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The influence of net community production and phytoplankton community structure on CO 2 uptake in the Gulf of Alaska
Global Biogeochemical Cycles
Abstract
Biological productivity is a key factor controlling the ocean's ability to take up carbon dioxide from the atmosphere. However, the ecological dynamics that drive regions of intense productivity and carbon export are poorly understood. In this study, we present high-spatial-resolution estimates of air-sea CO2 flux, net community production (NCP) rates calculated from O2/Ar ratios, and phytoplankton population abundances determined by continuous underway measurements on a cruise across the Gulf of Alaska in May 2010. The highest rates of NCP (249 ± 40 mmol C m-2 d-1) and oceanic CO2 uptake (air-sea flux of −42.3 ± 6.1 mmol C m-2 d-1) were observed across a transition zone between the high-nitrate low-chlorophyll (HNLC) waters of the Alaskan Gyre and the coastal waters off the Aleutian Islands. While the transition zone comprises 20% of the total area covered in crossing the Gulf of Alaska, it contributed 58% of the total NCP and 67% of the total CO2 uptake observed along the cruise track. A corresponding transition zone phytoplankton bloom was dominated by two small-celled (<20 µm) phytoplankton communities, which were distinct from the phytoplankton communities in the surrounding Alaskan Gyre and coastal waters. We hypothesize that mixing between iron-rich coastal waters and iron-limited Alaskan Gyre waters stimulated this bloom and fueled the high NCP and CO2 export observed in the region.
... This equation can be reorganized in a form reminiscent of the export ratio NCP=NPP proportion of variations in export/new production ratio. A similar relationship between NCP and NPP has also been observed in previous studies [Reuer et al., 2007;Palevsky et al., 2013;Stanley et al., 2010]. Therefore, we select the equation ...
... Although other parameters such as POC, band ratios, and inherent optical properties are likely strong predictors of NCP (Figure 4), they are omitted by GP, possibly because their relationships with NCP are not clearly expressed by our data set or because they are encompassed in the NPP parameterization [Behrenfeld and Falkowski, 1997;Behrenfeld et al., 2005;Westberry et al., 2008]. Interestingly, although VGPM and carbon-based production model (CbPM) estimates of NPP were both included in the pool of potential predictors, GP consistently selected VGPM over CbPM estimates of NPP, which is consistent with the results of Palevsky et al. [2013] in the Gulf of Alaska but in contrast to the recent results of Emerson [2014]. The difference may be attributed to the lack of time series observations in our training data set and representation of annual NCP (see discussion below on caveats and limitations). ...
... The satellite observations we use may also fail to capture some of the factors regulating NCP. For example, for a given NPP, regional differences in taxonomic composition Global Biogeochemical Cycles 10.1002/2015GB005314 may lead to differences in the relation of NCP to predictors [Boyd and Newton, 1995;Palevsky et al., 2013;Tremblay et al., 1997]. If NCP is a function of parameters that are not included in our algorithms or observable from satellites, deriving algorithms for specific oceanic biomes may improve predictions [e.g., Chang et al., 2014]. ...
We present two statistical algorithms for predicting global oceanic net community production (NCP) from satellite observations. To calibrate these two algorithms, we compiled a large data set of in situ O2/Ar-NCP and remotely sensed observations, including sea surface temperature (SST), net primary production (NPP), phytoplankton size composition, and inherent optical properties. The first algorithm is based on genetic programming (GP) which simultaneously searches for the optimal form and coefficients of NCP equations. We find that several GP solutions are consistent with NPP and SST being strong predictors of NCP. The second algorithm uses support vector regression (SVR) to optimize a numerical relationship between O2/Ar-NCP measurements and satellite observations. Both statistical algorithms can predict NCP relatively well, with a coefficient of determination (R2) of 0.68 for GP and 0.72 for SVR, which is comparable to other algorithms in the literature. However, our new algorithms predict more spatially uniform annual NCP distribution for the world's oceans and higher annual NCP values in the Southern Ocean and the five oligotrophic gyres.
... With respect to surface ocean carbon measurements, the Alaskan Gyre system remains extremely sparsely sampled. The seasonal air-sea CO 2 flux of the gyre has been described as being strongly influenced by gyre upwelling with outgassing in the winter and uptake in the summer (Brady et al., 2019;Palevsky et al., 2013;Chierici et al., 2006). Along the easternmost part of the North Pacific Current, most of our understanding comes from a limited region: the Ocean Station Papa mooring at 50 • N, 145 • W (Sutton et al., 2017) and the Line P Program (Freeland, 2007). ...
... The climatology is plotted over 19 months to emphasize the seasonal cycle. matological air-sea CO 2 flux (Brady et al., 2019;Palevsky et al., 2013;Chierici et al., 2006). The change in the sign of the flux is driven by a 40 µatm difference between winter maximum and summer minimum pCO 2 climatology values (Fig. 6b). ...
The global ocean takes up nearly a quarter of anthropogenic CO2 emissions annually, but the variability in this uptake at regional scales remains poorly understood. Here we use a neural network approach to interpolate sparse observations, creating a monthly gridded seawater partial pressure of CO2 (pCO2) data product from January 1998 to December 2019, at 1/12∘ × 1/12∘ spatial resolution, in the northeast Pacific open ocean, a net sink region. The data product (ANN-NEP; NCEI Accession 0277836) was created from pCO2 observations within the 2021 version of the Surface Ocean CO2 Atlas (SOCAT) and a range of predictor variables acting as proxies for processes affecting pCO2 to create nonlinear relationships to interpolate observations at a spatial resolution 4 times greater than leading global products and with better overall performance. In moving to a higher resolution, we show that the internal division of training data is the most important parameter for reducing overfitting. Using our pCO2 product, wind speed, and atmospheric CO2, we evaluate air–sea CO2 flux variability. On sub-decadal to decadal timescales, we find that the upwelling strength of the subpolar Alaskan Gyre, driven by large-scale atmospheric forcing, acts as the primary control on air–sea CO2 flux variability (r2=0.93, p<0.01). In the northern part of our study region, divergence from atmospheric CO2 is enhanced by increased local wind stress curl, enhancing upwelling and entrainment of naturally CO2-rich subsurface waters, leading to decade-long intervals of strong winter outgassing. During recent Pacific marine heat waves from 2013 on, we find enhanced atmospheric CO2 uptake (by as much as 45 %) due to limited wintertime entrainment. Our product estimates long-term surface ocean pCO2 increase at a rate below the atmospheric trend (1.4 ± 0.1 µatm yr−1) with the slowest increase in the center of the subpolar gyre where there is strong interaction with subsurface waters. This mismatch suggests the northeast Pacific Ocean sink for atmospheric CO2 may be increasing.
... The error bars in individual studies indicate the reported uncertainty. Numbers above or below the bars indicate the references: 1) Wong and Chan (1991), 2) Sutton et al. (2017), 3) Palevsky et al. (2013), 4) Chierici, Fransson and Nojiri (2006), etc. Details are in Table S1. ...
... Observed long-term changes in CO 2 fluxes show a clear increase in surface ocean CO 2 generally consistent with, or slightly weaker than the atmospheric CO 2 increase (Wong et al. 2010;Franco et al. 2021). Further north, the upwelling strength of the subpolar Alaskan Gyre has been shown to be the dominant control on surface carbonate chemistry seasonally ( Fig. 1; Chierici et al. 2006;Palevsky et al. 2013;Brady et al. 2019) and on longer timescales (Hauri et al. 2021). Increased winter wind speeds drive stronger gyre upwelling, bringing CO 2 -rich subsurface waters to the surface leading to seasonal outgassing (Chierici et al. 2006). ...
Improving our understanding of how the ocean absorbs carbon dioxide is critical to climate change mitigation efforts. We, a group of early career ocean professionals working in Canada, summarize current research and identify steps forward to improve our understanding of the marine carbon sink in Canadian national and offshore waters. We have compiled an extensive collection of reported surface ocean air–sea carbon dioxide exchange values within each of Canada's three adjacent ocean basins. We review the current understanding of air–sea carbon fluxes and identify major challenges limiting our understanding in the Pacific, the Arctic, and the Atlantic Ocean. We focus on ways of reducing uncertainty to inform Canada's carbon stocktake, establish baselines for marine carbon dioxide removal projects, and support efforts to mitigate and adapt to ocean acidification. Future directions recommended by this group include investing in maturing and building capacity in the use of marine carbon sensors, improving ocean biogeochemical models fit-for-purpose in regional and ocean carbon dioxide removal applications, creating transparent and robust monitoring, verification, and reporting protocols for marine carbon dioxide removal, tailoring community-specific approaches to co-generate knowledge with First Nations, and advancing training opportunities for early career ocean professionals in marine carbon science and technology.
... New production from Northwestern Pacific Ocean by satellite observation (Falkowski et al., 1998;Laws et al., 2000;Goes et al., 2000). NCP data are from the Station ALOHA (Ferroń et al., 2015), northeast subtropic and Alaskan Gyre (Lockwood et al., 2012;Palevsky et al., 2013). Sinking particles in the upper 200 m were collected by using drifting sediment traps (Honda et al., 2015) and 4810 m by using conical sediment trap (Nichiyu-Giken-Kogyo SMD26S-6000; Honda, 2020) at Station K2. ...
... The average NCP in the upwelling region of the UB was 55 ± 29 mmolC m −2 d −1 , which is about twice that in the ambient waters (24 ± 14 mmolC m −2 d −1 ; Table 3). The values from the UB are higher than those from the low-latitude Pacific region (7.9-26 mmolC m −2 d −1 ; Lockwood et al., 2012) and similar to, or lower than, those from high latitude regions such as Alaska (250 mmolC m −2 d −1 ; Palevsky et al., 2013). ...
The East Sea (also known as the Japan Sea; hereafter, EJS) is a semi-enclosed marginal sea surrounded by the Korean Peninsula, Russia, and the Japanese Islands. The EJS is connected to the Pacific through shallow straits. Thus, the EJS has its own thermohaline circulation and the characteristic biogeochemistry. The deep overturning circulation plays a critical role in carbon cycling including absorption of atmospheric CO2 and its sequestration into the interior of the sea. The turnover time of the deep EJS (>1000 m) is ~ hundred years and probably varies depending on physical climate forcing. Thus, the effect of climate change on oceanic processes may be more easily detected in the EJS. In this paper, we summarize the current understanding of carbon cycling in the EJS. We focus especially on the Ulleung Basin in the southwestern EJS, from which more extensive data are available. Notable features of carbon cycling in the EJS include the following: primary productivity and the export/production ratio are higher than in the adjacent Pacific; the EJS is a net sink of atmospheric CO2 and anthropogenic CO2 content is ~1% of the dissolved inorganic carbon inventory; dissolved inorganic carbon in the sea interior is mostly supplied by organic matter decomposition rather than CaCO3 dissolution and thus, the deep waters are vulnerable to acidification; N:P molar ratio of the deep waters is ~13, lower than the Redfield ratio; concentration of dissolved organic carbon is significantly higher than in the oceans; and sediment resuspension and lateral transport is an important component of sinking particulate organic carbon (POC) flux. Another important feature is the temporal trends observed for the last few decades. For example, pH, calcium carbonate saturation status, and dissolved oxygen concentration in the sea interior have decreased, whereas dissolved inorganic carbon and likely, the inventory of anthropogenic CO2 have increased. These temporal trends have an implication on better understanding of the processes occurring more slowly in the oceans. Brief suggestions for future research that will improve our understanding of carbon cycling and its variability are provided at the end of the paper.
... Measurements of the oxygen/argon (O 2 /Ar) dissolved gas ratio in the surface mixed layer trace the balance between photosynthesis and respiration, where net autotrophic conditions contribute to biological oxygen supersaturation, and comparison to argon, a noble gas with similar physical properties to oxygen, normalizes for physical drivers of oxygen supersaturation from bubble injection and temperature changes (Craig & Hayward, 2011;Emerson et al., 1991). The development of continuous underway methods to measure O 2 /Ar (Cassar et al., 2009;Kaiser et al., 2005;Tortell, 2005) has enabled new fine spatial-scale measurements which have been widely applied in both coastal and open ocean regions (Castro-Morales et al., 2013;Estapa et al., 2015;Eveleth et al., 2017;Hamme et al., 2012;Izett et al., 2018;Kaiser et al., 2005;Lockwood et al., 2012;Manning et al., 2017;Palevsky et al., 2013;Rosengard et al., 2020;Stanley et al., 2010;Tortell et al., 2015Tortell et al., , 2011Ulfsbo et al., 2014). These data are frequently combined with an estimate of air-sea gas exchange to calculate a rate of air-sea biological oxygen flux (termed "bioflux" by Jonsson et al., 2013), which under steady-state conditions with negligible physical flux of oxygen in out of the mixed layer, is equivalent to mixed layer NCP (equivalent to gross primary production minus community respiration). ...
... In high latitude systems, strong correlations between NCP and Chl are observed during the spring bloom (Tortell & Long, 2009), in summer (Tortell et al., 2012), and across a springtime productivity hotspot at the transition between the coastal and open ocean (Palevsky et al., 2013), but much weaker correlations after the peak of a bloom (Tortell et al., 2011). Conversely, a study in the equatorial Pacific found no correlation at all between NCP and Chl (Stanley et al., 2010). ...
The Kuroshio current separates from the Japanese coast to become the eastward flowing Kuroshio Extension (KE) characterized by a strong latitudinal density front, high levels of mesoscale (eddy) energy, and high chlorophyll a (Chl). While satellite measurements of Chl show evidence of the impact of mesoscale eddies on the standing stock of phytoplankton, there have been very limited synoptic, spatially resolved in situ estimates of productivity in this region. Here, we present underway measurements of oxygen/argon supersaturation (ΔO2/Ar), a tracer of net biological productivity, for the KE made in spring, summer, and early autumn. We find large seasonal differences in the relationships between ΔO2/Ar, Chl, and sea level anomaly (SLA), a proxy for local thermocline depth deviations driven by mesoscale eddies derived from satellite observations. We show that the KE is a pronounced hotspot of high ΔO2/Ar in spring, but corresponding surface Chl values are low and have no correlation with ΔO2/Ar. In summer, there is a hotspot of productivity associated with the Oyashio front, where ΔO2/Ar and Chl are strongly positively correlated. In autumn, ΔO2/Ar and Chl are consistently low throughout the region and also positively correlated. By combining our analysis of the in situ ΔO2/Ar data with complementary Argo, BGC‐Argo, repeat hydrography, and SLA observations, we infer the combination of physical and biological controls that drive the observed distributions of ΔO2/Ar and Chl. We find that the KE and Oyashio currents both act to supply nutrients laterally, fueling regions of high productivity in spring and summer, respectively.
... Studies have described correlations of community structures with patterns of primary production and carbon export in a variety of nutrient regimes [Pollard et al., 2009;Moreno-Ostos et al., 2011;Lockwood et al., 2012;Cassar et al., 2015]. Transition regions between higher and lower nutrient regions can be zones of high biomass and intensified production Ostle et al., 2015] with unique phytoplankton communities distinct from the regions to either side [Ribalet et al., 2010;Palevsky et al., 2013;Kavanaugh et al., 2014a]. ...
... GPP and NCP rates in the SST, SAG, and WTA agreed within standard deviations between this study (late March to early May) and the pooled incubation data (May and October). Higher NCP in the transition region compared to the subtropical gyre was consistent with results in other frontal regions Ostle et al., 2015;Palevsky et al., 2013] and may have been related to enhanced nutrient supply from the subpolar gyre [Ayers and Lozier, 2010;Palter et al., 2013]. Notably, both NCP and GPP rates in the SST had increased variability compared to other regions in this and the other studies; in particular, infrequent but high GPP and NCP features were separated from regionally typical values over distances of~100 km in both data sets. ...
In situ oxygen tracers (triple oxygen isotope and oxygen/argon ratios) were used to evaluate meridional trends in surface biological production and export efficiency across ~8000 km of the tropical and subtropical South Atlantic in March–May 2013. We used observations of picophytoplankton, nanophytoplankton, and microphytoplankton to evaluate community structure and diversity and assessed the relationships of these characteristics with production, export efficiency, and particulate organic carbon (POC) fluxes. Rates of productivity were relatively uniform along most of the transect with net community production (NCP) between 0 and 10 mmol O2 m−2 d−1, gross primary production (GPP) between 40 and 100 mmol O2 m−2 d−1, and NCP/GPP, a measure of export efficiency, ranging from 0.1 to 0.2 (0.05–0.1 in carbon units). However, notable exceptions to this basin-scale homogeneity included two locations with highly enhanced NCP and export efficiency compared to surrounding regions. Export of POC and particulate nitrogen, derived from sediment traps, correlated with GPP across the transect, over which the surface community was dominated numerically by picophytoplankton. NCP, however, did not correlate with POC flux; the mean difference between NCP and POC flux was similar to published estimates of dissolved organic carbon export from the surface ocean. The interrelated rates of production presented in this work contribute to the understanding, building on the framework of better-studied ocean basins, of how carbon is biologically transported between the atmosphere and the deep ocean.
... This organic matter is exported from surface waters by the biological and solubility carbon pumps (Stanley et al., 2010). Understanding the mechanisms driving these processes is vital for predicting how marine waters will respond to and influence climate change (Guo et al., 2012; Palevsky et al., 2013 ). Coastal regions in particular have high value to society but are also vulnerable to anthropogenic activities (Jickells, 1998). ...
... ties to reveal new insights into data collected for other purposes. To date, the majority of oxygen-based NCP estimates have focused on oceanic waters (Alkire et al., 2012). Emerson (2014) noted that coastal NCP values can be 3 times greater than open-ocean values; however, there are too few measurements to be confident in geographical variability. Palevsky et al. (2013) also found during their Gulf of Alaska O 2 /Ar survey that the transitional coastal zone contributed 58 % of the total NCP whilst representing only 20 % of the total area surveyed. The nature of the metabolic balance is particularly important in river-dominated margins, where high carbon and nutrient inputs stimulate primary production ...
Coastal seas represent one of the most valuable and vulnerable habitats on
Earth. Understanding biological productivity in these dynamic regions is
vital to understanding how they may influence and be affected by climate
change. A key metric to this end is net community production (NCP), the net
effect of autotrophy and heterotrophy; however accurate estimation of NCP has
proved to be a difficult task. Presented here is a thorough exploration and
sensitivity analysis of an oxygen mass-balance-based NCP estimation technique
applied to the Warp Anchorage monitoring station, which is a permanently
well-mixed shallow area within the River Thames plume. We have developed an
open-source software package for calculating NCP estimates and air–sea gas flux.
Our study site is identified as a region of net heterotrophy with strong
seasonal variability. The annual cumulative net community oxygen production
is calculated as (−5 ± 2.5) mol m−2 a−1. Short-term
daily variability in oxygen is demonstrated to make accurate individual daily
estimates challenging. The effects of bubble-induced supersaturation is shown
to have a large influence on cumulative annual estimates and is the source
of much uncertainty.
... Seasonally, the northern Alaskan Gyre region of our study area (latitudes north of 52N; Figure 6a&b), flips from outgassing in the wintertime to uptake in the summer in the climatological air-sea CO2 flux (Brady et al., 2019;Palevsky et al., 2013;Chierici et al., 2006). The change in the sign of the flux is driven by a 40 µatm difference between winter maxima and summer minima pCO2 climatology values (Figure 6b (Figure 6b), leading to outgassing (Figure 6a; Chierici et al. 2006). ...
The global ocean takes up nearly a quarter of anthropogenic CO2 emissions annually, but the variability of this uptake at regional scales remains poorly understood. Here we use a neural network approach to interpolate sparse observations, creating a monthly gridded seawater partial pressure of CO2 (pCO2) data product from January 1998 to December 2019, at 1/12° × 1/12° spatial resolution, in the Northeast Pacific open ocean. The data product (ANN-NEP; NCEI Record ID: BGSH2HNRP) was created from pCO2 observations within the 2021 version of the Surface Ocean CO2 Atlas (SOCAT), and a range of predictor variables acting as proxies for processes affecting pCO2 to create non-linear relationships to interpolate observations at a spatial resolution four times greater than leading global products and with better overall performance. In moving to a higher resolution, we show that the internal division of training data is the most important parameter for reducing overfitting. Using our pCO2 product, wind speed, and atmospheric CO2, we evaluate air-sea CO2 flux variability. On sub-decadal to decadal timescales, we find that the upwelling strength of the subpolar Alaskan Gyre, driven by large-scale atmospheric forcing, acts as the primary control on air-sea CO2 flux variability (r2 = 0.93, p < 0.01). In the northern part of our study region, divergence with atmospheric CO2 is enhanced by increased local wind stress curl, enhancing upwelling and entrainment of naturally CO2-rich subsurface waters, leading to decade-long intervals of strong winter outgassing. During recent Pacific marine heatwaves from 2013 on, we find enhanced atmospheric CO2 uptake (by as much as 45 %) due to limited wintertime entrainment. Our product estimates long-term surface ocean pCO2 increase at a rate below the atmospheric trend (1.4 ± 0.1 μatm yr−1) with the slowest increase in the center of the subpolar gyre where there is strong interaction with subsurface waters. This mismatch suggests the Northeast Pacific Ocean sink for atmospheric CO2 may be increasing.
... NCP regulates the CO 2 dynamics in the upper ocean box by exporting photosynthetic organic carbon and releasing CO 2 through community respiration, thereby influencing the concentrations of CO 2 at the sea surface and even the exchange of CO 2 with the atmosphere (Jiang et al., 2019;Plant et al., 2016). As a crucial parameter that can provide insights into whether marine ecosystems function as carbon sources or carbon sinks, NCP has been extensively investigated in various marine regions (Bushinsky and Emerson, 2015;Huang et al., 2018;Palevsky et al., 2013). However, due to the constraints of ship-based discrete observations, research on the coupling effect between NCP and sea surface CO 2 dynamics in highly variable estuaries is still limited, which hinders our understanding of the carbon source-sink dynamics at the air-sea interface. ...
Estuaries are crucial components of the global ocean carbon cycle due to their high productivity. However, our understanding of the carbon source-sink dynamics at the air-sea interface of estuaries is incomplete, largely due to the rapidly changing environmental conditions. To address this, we conducted a study in early autumn 2016 using high-resolution biogeochemical data collected through buoy observations in the Changjiang River plume (CRP). Using a mass balance approach, we examined the factors driving changes in the sea surface partial pressure of carbon dioxide (pCO2) and quantified the net community production (NCP) in the mixed layer. We also explored the relationship between NCP and the carbon source-sink dynamics at the air-sea interface. Our results revealed that biological activities (64.0 %) and seawater mixing (19.7 %, including lateral transport and vertical mixing) were the dominant factors controlling changes in sea surface pCO2 during the study period. Moreover, NCP in the mixed layer was affected by factors such as light availability and the presence of respired organic carbon associated with vertical mixing of seawater. Notably, we observed a strong correlation between NCP and the difference in pCO2 between air and sea (δpCO2), with a threshold NCP value of 308.4 mmol m-2 d-1 identified as an indicator of the transition from a CO2 source to a sink in the CRP. Hence, we suggest that the NCP in a specific ocean box has a threshold, beyond which the air-sea interface in estuaries will change from a carbon source to a carbon sink, and vice versa.
... Both elevated productivity and better organic matter preservation could have been important for increasing deep ocean and sediment storage of organic matter, and potentially drawing down atmospheric CO 2 and cooling the climate (e.g., Burdige, 2007) under short (orbital) time scales (e.g., during low eccentricity intervals in the MPWP; de la Vega et al., 2020, Figure 5b), and longer time scales (e.g., across the PPT). In addition, high marine diversity during the late Pliocene might have slowly contributed to atmospheric CO 2 drawdown as suggested for the present day (Palevsky et al., 2013). Globally, the atmospheric CO 2 decreased about 100 ppm during the PPT (Figure 5b), where 40% of the modern decadal atmospheric CO 2 variability has been attributed to ocean forcing (DeVries et al., 2019). ...
The modern Gulf of Alaska (GOA) is a Cordilleran Ice Sheet (CIS) region, estimated to be important for nutrient cycling and CO2 exchange. Little is known of the GOA evolution over the Pliocene and Pleistocene as well as its impact on the CIS development, when other evidence for changing North Pacific circulation has emerged. We analyzed Integrated Ocean Drilling Program Expedition 341 Site U1417 sediments, which extend through the Plio‐Pleistocene transition (4–1.7 Ma), focusing on productivity‐related biomarkers (alkenones, brassicasterol), siliceous microfossils and bulk carbon and nitrogen stable isotopes. Our results show two dominant water column regimes: one characterized by high silica and low organic matter (OM) preservation, containing microorganism remains from a mix of habitats (4–3.7 Ma) and a second characterized by low biogenic silica and increased OM preservation of microorganisms from dominantly open ocean habitats (3.33–3.32 Ma and 2.8–1.66 Ma). An increase of phytoplankton diversity (3.7–3.35 Ma, 3.19–2.82 Ma) characterizes the two transitions of water column conditions, from oxygenated to reductive, that we attribute to a change from ocean mixing to strong stratified conditions with some occasional mixing. The biogeochemical changes in the GOA follow 400 and 100 kyr eccentricity cycles which are also reflected in changes in the CIS. We conclude that the CIS expansion created high nutrient low chlorophyll conditions in the GOA during the Mid Piacenzian Warm Period and the early Pleistocene. In turn, positive feedbacks increased marine productivity export, atmospheric CO2 drawdown and further CIS expansion.
... They have a disproportionately large impact, relative to their surface area, on global carbon cycling (Thomas, 2004) as shelf seas provide 10 %-30 % of all marine primary production while comprising less than 10 % of the ocean surface (Harris et al., 2014;Sharples et al., 2019). Given their global role in carbon cycling, understanding the mechanisms driving primary production is vital for predicting how shelf systems will respond to and influence climate change (Palevsky et al., 2013;Legge et al., 2020). ...
The continental shelf seas are important at a global scale for ecosystem services.
These highly dynamic regions are under a wide range of stresses, and as such future management requires appropriate monitoring measures.
A key metric to understanding and predicting future change are the rates of biological production.
We present here the use of an autonomous underwater glider with an oxygen (O2) and a wet-chemical microfluidic total oxidised nitrogen (NOx-=NO3-+NO2-) sensor during a spring bloom as part of a 2019 pilot autonomous shelf sea monitoring study.
We find exceptionally high rates of net community production using both O2 and NOx- water column inventory changes,
corrected for air–sea gas exchange in case of O2.
We compare these rates with 2007 and 2008 mooring observations finding similar rates of NOx- consumption.
With these complementary methods we determine the O2:N amount ratio of the newly produced organic matter (7.8 ± 0.4) and the overall O2:N ratio for the total water column (5.7 ± 0.4).
The former is close to the canonical Redfield O2:N ratio of 8.6 ± 1.0,
whereas the latter may be explained by a combination of new organic matter production and preferential remineralisation of more reduced organic matter at a higher O2:N ratio below the euphotic zone.
... The approach has thus far exclusively been used at the ocean surface to estimate biological oxygen fluxes and net community production (Cassar et al., 2009(Cassar et al., , 2011Gueguen & Tortell, 2008;Hamme et al., 2012;Huang et al., 2012;Long et al., 2011;Palevsky et al., 2013;Reuer et al., 2007;Spitzer & Jenkins, 1989). [ ] [ ] Ar Ar / sat on the very right-hand side of Equation 6 is generally assumed at saturation, but can be measured (Hamme & Emerson, 2002) (Eveleth et al., 2014(Eveleth et al., , 2017. ...
In the subsurface ocean, O2 depleted because of organic matter remineralization is generally estimated based on apparent oxygen utilization (AOU). However, AOU is an imperfect measure of oxygen utilization because of O2 air‐sea disequilibrium at the site of deepwater formation. Recent methodological and instrumental advances have paved the way to further deconvolve the processes driving the O2 signature. Using numerical model simulations of the global ocean, we show that the measurements of the dissolved O2/Ar ratio, which so far have been confined to the ocean surface, can provide improved estimates of oxygen utilization, especially in regions where the disequilibrium at the site of deepwater formation is associated with physical processes. We discuss applications of this new approach and implications for the current tracers relying on O2 such as remineralization ratios, respiratory quotients, and preformed nutrients. Finally, we propose a new composite geochemical tracer, [O2]bio* combining dissolved O2/Ar and phosphate concentration. Being insensitive to photosynthesis and respiration, the change in this new tracer reflects gas exchange at the air‐sea interface at the sites of deepwater formation.
... An additional biological influence on the air-sea CO 2 flux has been posited: Phytoplankton community structure is expected to have a dominant effect (Hilligsoe et al., 2011), with functional types such as diatoms thought to export organic carbon most efficiently (Michaels & Silver, 1988). However, small phytoplankton have also been found to influence CO 2 uptake and export (Palevsky et al., 2013;Richardson & Jackson, 2007), and in the North Atlantic dinoflagellate abundance was found to strongly correlate with organic carbon flux at 2,000 m (Henson et al., 2012). While calcifying phytoplankton (e.g., coccolithophores) can also modify seawater pCO 2 during formation, they may also contribute to efficient organic carbon transfer to depth (Klaas & Archer, 2002). ...
The North Atlantic is a substantial sink for anthropogenic CO2. Understanding the mechanisms driving the sink's variability is key to assessing its current state and predicting its potential response to global climate change. Here we apply a time series decomposition technique to satellite and in situ data to examine separately the factors (both biological and nonbiological) that affect the sea-air CO2 difference (ΔpCO2) on seasonal and interannual time scales. We demonstrate that on seasonal time scales, the subpolar North Atlantic ΔpCO2 signal is predominantly correlated with biological processes, whereas seawater temperature dominates in the subtropics. However, the same factors do not necessarily control ΔpCO2 on interannual time scales. Our results imply that the mechanisms driving seasonal variability in ΔpCO2 cannot necessarily be extrapolated to predict how ΔpCO2, and thus the North Atlantic CO2 sink, may respond to increases in anthropogenic CO2 over longer time scales.
... Plankton biodiversity supports critical ecosystem services such as the production of oxygen, the removal of atmospheric carbon, and the provision of food for commercial fish stocks, all of which are under pressure due to climate change [75,76]. For example, the size structure and species composition of phytoplankton communities is related to oxygen production and the removal of atmospheric carbon, ecosystem services which are likely to alter due to climate change [77]. Similarly, warming seas have caused a transition of Northeast Atlantic plankton communities from a community dominated by cold-water organisms with large body sizes to a more biodiverse community characterised by smaller warm-water organisms, coinciding with decreased carbon export [78]. ...
Taxonomic information provides a crucial understanding of the most basic component of biodiversity – which organisms are present in a region or ecosystem. Taxonomy, however, is a discipline in decline, at times perceived as ‘obsolete’ due to technical advances in science, and with fewer trained taxonomists and analysts emerging each year to replace the previous generation as it retires. Simultaneously, increasing focus is turned towards sustainable management of the marine environment using an ecosystem approach, and towards conserving biodiversity, key species, and habitats. Sensitive indicators derived from taxonomic data are instrumental to the successful delivery of these efforts. At the base of the marine food web and closely linked to their immediate environment, plankton are increasingly needed as indicators to support marine policy, inform conservation efforts for higher trophic organisms, and protect human health. Detailed taxonomic data, containing information on the presence/absence and abundance of individual plankton species, are required to underpin the development of sensitive species- and community-level indicators which are necessary to understand subtle changes in marine ecosystems and inform management and conservation efforts. Here the critical importance of plankton taxonomic data is illustrated, and therefore plankton taxonomic expertise, in informing marine policy and conservation and outline challenges, and potential solutions, facing this discipline.
... The VGPM comes closest to reproducing geochemically observed PP rates at OSP and in the container ship regions, while the CbPM underestimates PP as compared to the geochemically determined rates. Similarly, a previous study in the Gulf of Alaska showed that VGPM-based EP matched O 2 /Ar-based EP in a springtime high-productivity hot spot, whereas it was not detected in CbPM-based EP [Palevsky et al., 2013]. However, the VGPM significantly underestimates PP in the subtropics ( Figure 2) and also underestimates winter and spring PP in the container ship regions (Figure 3). ...
Estimates of primary and export production (PP and EP) based on satellite remote sensing algorithms and global biogeochemical models are widely used to provide year-round global coverage not available from direct observations. However, observational data to validate these approaches are limited. We find that no single satellite algorithm or model can reproduce seasonal and annual geochemically-determined PP, export efficiency (EP/PP) and EP rates throughout the North Pacific basin, based on comparisons throughout the full annual cycle at time series stations in the subarctic and subtropical gyres and basin-wide regions sampled by container ship transects. The high latitude regions show large PP discrepancies in winter and spring and strong effects of deep winter mixed layers on annual EP that cannot be accounted for in current satellite-based approaches. These results underscore the need to evaluate satellite- and model-based estimates using multiple productivity parameters measured over broad ocean regions throughout the annual cycle.
... Uncertainty in the air-sea gas exchange rate is estimated by assuming that the majority of uncertainty results from the parameterized relationship between gas exchange rate (k) and wind speed and that the spread between the air-sea gas exchange rates calculated from the Liss and Merlivat [1986] and Wanninkhof [1992] equations represents 95% of the variability (±2σ) in k [Palevsky et al., 2013], yielding a mean uncertainty in k of ±14% over all discrete sample locations in the data set. ...
We measured triple oxygen isotopes and oxygen/argon dissolved gas ratios as non-incubation based geochemical tracers of gross oxygen production (GOP) and net community production (NCP) on sixteen container ship transects across the North Pacific from 2008-2012. We estimate rates and efficiency of biological carbon export throughout the full annual cycle across the North Pacific basin (35°N – 50°N, 142°E – 125°W) by constructing mixed layer budgets that account for physical and biological influences on these tracers. During the productive season from spring through fall, GOP and NCP are highest in the Kuroshio region west of 170°E and decrease eastward across the basin. However deep winter mixed layers (>200 m) west of 160°W ventilate ~40-90% of this seasonally exported carbon while only ~10% of seasonally exported carbon east of 160°W is ventilated in winter where mixed layers are <120 m. As a result, despite higher annual GOP in the west than the east, the annual carbon export (sequestration) rate and efficiency decrease westward across the basin from export of 2.3 ± 0.3 mol C m-2 yr-1 east of 160°W to 0.5 ± 0.7 mol C m-2 yr-1 west of 170°E. Existing productivity rate estimates from time-series stations are consistent with our regional productivity rate estimates in the eastern but not western North Pacific. These results highlight the need to estimate productivity rates over broad spatial areas and throughout the full annual cycle including during winter ventilation in order to accurately estimate the rate and efficiency of carbon sequestration via the ocean's biological pump.
... We note both methods perform poorly at the end of this cruise. The difficulty comes from a short section of the third segment of the cruise, where the population density shifted rapidly due to a passage into a different oceanic environment (Palevsky et al., 2013), a shift which is detected by the change-point detection algorithm. Unfortunately, this shift is accompanied by a massive drop in the amount of data collected per three minute window. ...
Motivation:
Recent technological innovations in flow cytometry now allow oceanographers to collect high-frequency flow cytometry data from particles in aquatic environments on a scale far surpassing conventional flow cytometers. The SeaFlow cytometer continuously profiles microbial phytoplankton populations across thousands of kilometers of the surface ocean. The data streams produced by instruments such as SeaFlow challenge the traditional sample-by-sample approach in cytometric analysis and highlight the need for scalable clustering algorithms to extract population information from these large-scale, high-frequency flow cytometers.
Results:
We explore how available algorithms commonly used for medical applications perform at classification of such a large-scale, environmental flow cytometry data. We apply large-scale Gaussian mixture models (GMM) to massive data sets using Hadoop. This approach outperforms current state-of-the-art cytometry classification algorithms in accuracy, and can be coupled with manual or automatic partitioning of data into homogeneous sections for further classification gains. We propose the GMM with partitioning approach for classification of large-scale, high-frequency flow cytometry data.
Contact:
hyrkas@cs.washington.edu.
... Emerson (2014) noted that coastal NCP values can be three times greater than open ocean values, however, there are too few measurements to be confident in geographical variability. Palevsky et al. (2013) also found during their Gulf of Alaska O 2 /Ar survey that the transitional coastal zone contributed 58 % of 10 the total NCP whilst representing only 20 % of the total area surveyed. The nature of the metabolic balance is particularly important in river-dominated margins, where high carbon and nutrient inputs stimulate primary production and microbial respiration with large seasonal variations (Guo et al., 2012). ...
Coastal seas represent one of the most valuable and vulnerable habitats on Earth. Understanding biological productivity in these dynamic regions is vital to understanding how they may influence and be affected by climate change. A key metric to this end is net community production (NCP), the net effect of autotrophy and hetrotrophy, however accurate estimation of NCP has proved to be a difficult task. Presented here is a thorough exploration and sensitivity analysis of an oxygen mass-balance based NCP estimation technique applied to the Warp Anchorage monitoring station which is a permanently well mixed shallow area within the Thames river plume. We have developed an open source software package for calculating NCP estimates and air-sea gas flux. Our study site is identified as a region of net heteotrophy with strong seasonal variability. The annual cumulative net community oxygen production is calculated as (−5 ± 2.5) mol m−2 a−1. Short term daily variability in oxygen is demonstrated to make accurate individual daily estimates challenging. The effects of bubble induced supersaturation is shown to have a large influence on cumulative annual estimates, and is the source of much uncertainty.
... Mainly, O 2 /Ar reflects the balance between photosynthesis and respiration, i.e., net community production (NCP). The O 2 /Ar approach is increasingly being adopted by various groups Hamme et al., 2012;Huang et al., 2012;Palevsky et al., 2013;Reuer et al., 2007;Spitzer and Jenkins, 1989;Stanley et al., 2010], with new methods allowing for high-resolution measurements [e.g., Cassar et al., 2009;Tortell, 2005]. However, the O 2 /Ar-NCP approach harbors limitations and uncertainties, some of which are described below. ...
The O2/Ar approach has become a key method to estimate oceanic net community production (NCP). However, in some seasons and regions of the ocean, strong vertical mixing of O2-depleted deepwater introduces a large error into O2/Ar-derived NCP estimates. In these cases, undersaturated-O2/Ar observations have for all intents and purposes been ignored. We propose to combine underway O2/Ar and N2O observations into a composite tracer that is conservative with respect to the influence of vertical mixing on the surface biological O2 inventory. We test the proposed method with an ocean observing system simulation experiment (OSSE) in which we compare N2O-O2/Ar and O2/Ar-only gas flux estimates of NCP to the model-simulated true NCP in the Southern Ocean. Our proof-of-concept simulations show that the N2O-O2/Ar tracer significantly improves NCP estimates when/where vertical mixing is important.
... Our high NCP O2/Ar (up to 6 mol C m À2 ) in the marginal sea ice zone are of the same order of magnitude as estimates from the productive Bering Sea region based on the drawdown of DIC and nutrients [Cross et al., 2012;Mathis et al., 2010], as well as mean NCP rates (88 ± 15 mmol C m À2 d À1 ) estimated for the coastal region of the Gulf of Alaska from Δ(O 2 /Ar) measurements [Palevsky et al., 2013]. The high rates are also comparable to previous estimates of new production associated with ice-edge phytoplankton blooms [e.g., Mundy et al., 2009] which are significant features of Arctic primary production [Sakshaug, 2004] and occur in all seasonally ice-covered areas from spring to late summer [Perrette et al., 2011, and references therein]. ...
Large-scale patterns of net community production (NCP) were estimated during the late summer cruise ARK-XXVI/3 (TransArc, Aug/Sep 2011) to the central Arctic Ocean. Several approaches were used based on: (i) continuous measurements of surface water oxygen to argon ratios (O2/Ar), (ii) underway measurements of surface partial pressure of carbon dioxide (pCO2), (iii) discrete samples of dissolved inorganic carbon (DIC), and (iv) dissolved inorganic nitrogen and phosphate. The NCP estimates agreed well within the uncertainties associated with each approach. The highest late summer NCP (up to 6 mol C m−2) was observed in the marginal sea ice zone region. Low values (<1 mol C m−2) were found in the sea-ice covered deep basins with a strong spatial variability. Lowest values were found in the Amundsen Basin and moderate values in the Nansen and Makarov Basins with slightly higher estimates over the Mendeleev Ridge. Our findings support a coupling of NCP to sea ice coverage and nutrient supply and thus stress a potential change in spatial and temporal distribution of NCP in a future Arctic Ocean. To follow the evolution of NCP in space and time, it is suggested to apply one or several of these approaches in shipboard investigations with a time interval of three to five years.
Total mercury concentrations ([THg]) exceed thresholds of concern in some Steller sea lion (Eumetopias jubatus) tissues from certain portions of the Aleutian Islands, Alaska. We applied compound-specific stable isotope analyses of both carbon and nitrogen in amino acids from fish muscle tissue to quantify the proportional contributions of primary production sources and trophic positions of eight prey species (n = 474 total) that are part of Steller sea lion diets. Previous THg analyses of fish muscle, coupled with monomethylmercury analyses of a subset of samples, substantiated previous findings that fishes from the west of Amchitka Pass, a discrete oceanographic boundary of the Aleutian Archipelago, have higher muscle Hg concentrations relative to fishes from the east. The δ13C values of essential amino acids (EAAs) in fish muscle demonstrated that although most fishes obtained their EAAs primarily from algae, some species varied in the extent to which they relied on this EAA source. The δ15N values of phenylalanine (0.9 to 7.8 ‰), an indicator of the isotopic baseline of a food web, varied widely within and among fish species. Trophic position estimates, accounting for this baseline variation, were higher from the west relative to the east of the pass for some fish species. Trophic magnification slopes using baseline-corrected trophic position estimates indicated similar rates of Hg biomagnification to the east and west of Amchitka Pass. Multiple linear regression models revealed that trophic position was the most important driver of fish muscle [THg] with less variation explained by other parameters. Thus, higher trophic positions but not the rate of Hg biomagnification to the west of Amchitka Pass may play a role in the regional differences in both fish and Steller sea lion [THg]. Although, differences in Hg contamination and uptake at the base of the east and west food webs could not be excluded.
As a tree of considerable importance in arid regions—date palm, Phoenix dactylifera L. survival in contaminated areas of Sfax city has drawn our attention. Leaf samples of the plants grown in the study area showed high levels of cadmium (Cd), copper (Cu), and chromium (Cr). On the basis of this finding, the cellular mechanisms that explain these metal accumulations were investigated in controlled conditions. After four months of exposure to Cd, Cr, or Cu, high bioconcentration and translocation factor (TF>1) have been shown for date palm plantlets exposed to Cd and low TF values were obtained for plantlets treated with Cr and Cu. Moreover, accumulation of oxidants and antioxidant enzyme activities occurred in exposed roots to Cu and Cd. Secondary metabolites, such as polyphenols and flavonoids, were enhanced in plants exposed at low metal concentrations and declined thereafter. Accumulation of flavonoids in cells may be correlated with the expression of the gene encoding Pdmate5, responsible for the transport of secondary metabolites, especially flavonoids. Other transporter genes responded positively to metal incorporation, especially Pdhma2, but also Pdabcc and Pdnramp6. The latter would be a new candidate gene sensitive to metallic stress in plants. Expressions of gene coding metal chelators were also investigated. Pdpcs1 and Pdmt3 exhibited a strong induction in plants exposed to Cr. These modifications of the expression of some biochemical and molecular based-markers in date palm helped to better understand the ability of the plant to tolerate metals. They could be useful in assessing heavy metal contaminations in polluted soils and may improve accumulation capacity of other plants.
Phytoplankton growth in the Gulf of Alaska (GoA) is limited by iron (Fe), yet Fe sources are poorly constrained. We examine the temporal and spatial distributions of Fe, and its sources in the GoA, based on data from three cruises carried out in 2010 from the Copper River (AK) mouth to beyond the shelf break. April data are the first to describe late winter Fe behavior before surface water nitrate depletion began. Sediment resuspension during winter and spring storms generated high “total dissolvable Fe” (TDFe) concentrations of ~1000 nmol kg ⁻¹ along the entire continental shelf, which decreased beyond the shelf break. In July, high TDFe concentrations were similar on the shelf, but more spatially variable, and driven by low‐salinity glacial meltwater. Conversely, dissolved Fe (DFe) concentrations in surface waters were far lower and more seasonally consistent, ranging from ~4 nmol kg ⁻¹ in nearshore waters to ~0.6–1.5 nmol kg ⁻¹ seaward of the shelf break during April and July, despite dramatic depletion of nitrate over that period. The reasonably constant DFe concentrations are likely maintained during the year across the shelf by complexation by strong organic ligands, coupled with ample supply of labile particulate Fe. The April DFe data can be simulated using a simple numerical model that assumes a DFe flux from shelf sediments, horizontal transport by eddy diffusion, and removal by scavenging. Given how global change is altering many processes impacting the Fe cycle, additional studies are needed to examine controls on DFe in the Gulf of Alaska.
We evaluate the influences of biological carbon export, physical circulation, and temperature-driven solubility changes on air-sea CO2 flux across the North Pacific basin (35°N–50°N, 142°E–125°W) throughout the full annual cycle by constructing mixed layer budgets for dissolved inorganic carbon (DIC) and pCO2, determined on fifteen container ship transects between Hong Kong and Long Beach, CA from 2008 to 2012. Annual air-sea CO2 flux is greatest in the western North Pacific and decreases eastward across the basin (2.7 ± 0.9 mol C m-2 yr-1 west of 170°E, as compared to 2.1 ± 0.3 mol C m-2 yr-1 east of 160°W). East of 160°W, DIC removal by annual net community production (NCP) more than fully offsets the DIC increase due to air-sea CO2 flux. However, in the region west of 170°E influenced by deep winter mixing, annual NCP only offsets ~20% of the DIC increase due to air-sea CO2 flux, requiring significant DIC removal by geostrophic advection. Temperature-driven solubility changes have no net influence on pCO2 and account for <25% of annual CO2 uptake. The seasonal timing of NCP strongly affects its influence on air-sea CO2 flux. Biological carbon export from the mixed layer has a stronger influence on pCO2 in summer when mixed layers are shallow, but changes in pCO2 have a stronger influence on air-sea CO2 flux in winter when high wind speeds drive more vigorous gas exchange. Thus it is necessary to determine the seasonal timing as well as the annual magnitude of NCP to determine its influence on ocean carbon uptake.
Western boundary currents support high primary production and carbon export. Here, we performed a survey of photosynthetic picoeukaryotes in the North Pacific Ocean in four transects crossing the Kuroshio Front. Prasinophyte algae comprised 85% of 18S rRNA gene sequences for photosynthetic taxa in the <5 μm size fraction. The picoplanktonic (<2 μm) genera Micromonas and Ostreococcus comprised 30% and 51% of the total photosynthetic 18S rDNA sequences from five stations. Phylogenetic analysis showed that two Ostreococcus ecotypes, until now rarely found to co-occur, were both present in the majority of samples. Ostreococcus ecotype OI reached 6,830 ± 343 gene copies mL−1, while Ostreococcus ecotype OII reached 50,190 ± 971 gene copies mL−1 based on qPCR analysis of the 18S rRNA gene. These values are higher than in studies of other oceanographic regions by a factor of 10 for OII. The data suggest that meso- and finer-scale physical dynamics had a significant impact on the populations at the front, either by mingling ecotypes from different source regions at fine scales (∼10s km) or by stimulating their growth through vertical nutrient injections. We investigate this hypothesis with an idealized diffusion-reaction model, and find that only a combination of mixing and positive net growth can explain the observed distributions and overlap of the two Ostreococcus ecotypes. Our field observations support larger-scale numerical ocean simulations that predict enhanced biodiversity at western boundary current fronts, and suggest a strategy for systematically testing that hypothesis.
The integration of cytometers with autonomous surface and underwater vehicles can facilitate a more thorough understanding of ocean plankton types and their spatiotemporal distribution. This paper reviews existing and emerging cytometers that could potentially be integrated, with an eye toward constraints and capabilities. Vehicles have payload size and power constraints that must be considered when evaluating instrument designs for payload integration. The candidate cytometer capabilities, including dynamic range for particle-size detection, must also be taken into account to accomplish mission goals.
In this paper, we use an observational dataset built from Argo in situ profiles to describe the main large-scale patterns of intraseasonal mixed layer depth (MLD) variations in the Indian Ocean. An eddy permitting (0.25°) regional ocean model that generally agrees well with those observed estimates is then used to investigate the mechanisms that drive MLD intraseasonal variations and to assess their potential impact on the related SST response. During summer, intraseasonal MLD variations in the Bay of Bengal and eastern equatorial Indian Ocean primarily respond to active/break convective phases of the summer monsoon. In the southern Arabian Sea, summer MLD variations are largely driven by seemingly-independent intraseasonal fluctuations of the Findlater jet intensity. During winter, the Madden-Julian Oscillation drives most of the intraseasonal MLD variability in the eastern equatorial Indian Ocean. Large winter MLD signals in northern Arabian Sea can, on the other hand, be related to advection of continental temperature anomalies from the northern end of the basin. In all the aforementioned regions, peak-to-peak MLD variations usually reach 10 m, but can exceed 20 m for the largest events. Buoyancy flux and wind stirring contribute to intraseasonal MLD fluctuations in roughly equal proportions, except for the Northern Arabian Sea in winter, where buoyancy fluxes dominate. A simple slab ocean analysis finally suggests that the impact of these MLD fluctuations on intraseasonal sea surface temperature variability is probably rather weak, because of the compensating effects of thermal capacity and sunlight penetration: a thin mixed-layer is more efficiently warmed at the surface by heat fluxes but loses more solar flux through its lower base.
A new 2° resolution global climatology of the mixed layer depth (MLD) based on individual profiles is constructed. Previous global climatologies have been based on temperature or density‐gridded climatologies. The criterion selected is a threshold value of temperature or density from a near‐surface value at 10 m depth (Δ T = 0.2°C or Δσ θ = 0.03 kg m ⁻³ ). A validation of the temperature criterion on moored time series data shows that the method is successful at following the base of the mixed layer. In particular, the first spring restratification is better captured than with a more commonly used larger criteria. In addition, we show that for a given 0.2°C criterion, the MLD estimated from averaged profiles results in a shallow bias of 25% compared to the MLD estimated from individual profiles. A new global seasonal estimation of barrier layer thickness is also provided. An interesting result is the prevalence in mid‐ and high‐latitude winter hemispheres of vertically density‐compensated layers, creating an isopycnal but not mixed layer. Consequently, we propose an optimal estimate of MLD based on both temperature and density data. An independent validation of the maximum annual MLD with oxygen data shows that this oxygen estimate may be biased in regions of Ekman pumping or strong biological activity. Significant differences are shown compared to previous climatologies. The timing of the seasonal cycle of the mixed layer is shifted earlier in the year, and the maximum MLD captures finer structures and is shallower. These results are discussed in light of the different approaches and the choice of criterion.
A climatology of the winter mixed layer in the North Pacific Ocean was constructed using hydrographic data from historical archives and recent observational programs, including the World Ocean Circulation Experiment. The main aim was to provide better knowledge about source areas of upper water masses. The authors have endeavored to preserve water properties near the frontal regions by keeping the smoothing scale as small as possible. The resulting climatology shows considerable differences in the mixed layer depth and its water properties from those derived from the World Ocean Atlas (WOA). Maps of the potential vorticity field of the North Pacific pycnocline are presented using the isopycnally averaged climatology, HydroBase. Three distinct lateral minima of potential vorticity are identified as Subtropical Mode Water (STMW), Central Mode Water (CMW), and Eastern Subtropical Mode Water (ESTMW), in the western, central, and eastern parts of the subtropical gyre, respectively. The HydroBase isopycnal climatology is more consistent with the present mixed layer climatology than with the mixed layer from WOA in the sense that the former represents the formation of all mode waters more adequately. The STMW and ESTMW formation areas are associated with the mixed layer front and the small horizontal gradient of the mixed layer density, respectively, which confirms previously proposed formation mechanisms. That is, the low potential vorticity of STMW and ESTMW results from the large lateral induction and the small cross-isopycnal flow, respectively. The CMW formation area is not primarily associated with the mixed layer front, which contrasts with previous ideas. It is suggested that low potential vorticity of CMW is mainly caused by small cross-isopycnal flow rather than through large lateral induction rate. Additional new features of subtropical pycnocline ventilation revealed by the HydroBase isopycnal climatology are also discussed.
Concentrations of soluble (<0.025μm), dissolved (<0.4μm) and total (unfiltered) iron (Fe) were measured over the continental shelf and slope of the northern Gulf of Alaska (GoA) during spring-summer. Large cross-shelf gradients of surface water Fe concentrations were observed in these productive shelf waters during both seasons. Most of the particulate (>0.4 μm) and colloidal (0.025-0.4 μm) Fe size fractions were removed from surface waters within the inner and mid shelf. As a result the contribution of soluble Fe to the total Fe concentration increased from the inner shelf to the shelf break/slope waters. Surface water dissolved Fe concentrations on the northern GoA continental slope were higher than those previously observed in the central GoA gyre. Variations in surface water Fe concentrations from spring through summer appear to result from the changes in freshwater discharge and physical processes on the shelf.
There has been considerable debate about both the mechanisms controlling primary production, and the interpretation of data from Fe-enrichment experiments conducted in high nitrate-low chlorophyll (HNLC) regions. This paper presents results of 3 in vitro Fe-enrichment experiments performed in May 1993 and May 1994 at Ocean Station Papa (OSP) in the NE subarctic Pacific. Expt 1 (May 1993) considered jointly the influence of both Fe supply and microzooplankton herbivory on algal stocks, while the second (May 1993) investigated the influence of Fe supply on the partitioning of C, N and Fe between algal size classes. The third study (May 1994) monitored changes in phytoplankton stocks in Fe-enriched carboys containing mesozooplankton. Assuming similar environmental conditions in May 1993 and 1994, then the combined findings indicate that under ambient conditions autotrophic cells <5 mu m compose >70 % of algal biomass, primarily utilized ammonium, showed no Fe-mediated enhancement of N-normalized nitrate or ammonium uptake, and were thus unlikely to be Fe-limited. Although the coupling between grazer mortality and algal growth of these cells (g/mu) was ca 0.71 +/- 0.25, they grew at close to maximal rates but exhibited negligible net growth rates, suggesting strong grazer control. Dissolved iron (DFe) supply promoted a rapid increase in the abundance of large, initially rare, diatoms (mainly Nitzschia spp.) over 6 d, elevated diatom growth rates to close to their theoretical maximum and increased rates of incorporation of N-normalized nitrate and Fe by these cells over time. Unlike the small cells, stocks of large autotrophs also increased in the controls; DFe measurements indicate that this was probably due to inadvertent Fe contamination. The development of a phytoplankton population, of a cell size probably too large to be grazed at a significant rate by microzooplankton, resulted in a decoupling of herbivory and algal growth. In addition, mesozooplankton herbivory appeared unable to prevent the accumulation of these large cells; in May 1994, Fe supply prompted an 8-fold increase in algal stocks over 6 d in carboys where grazers equivalent to the maximum annual in situ pelagic abundance were present. The findings agree with the theories of others, that Fe supply rather than grazing provides the ultimate control over the phytoplankton community in the NE subarctic Pacific.
In this chapter we attempt to present a brief introduction to the subject of air-sea gas exchange. First the basic equations governing such exchange are given, then a review of some models proposed to describe the gas transfer process. Following this, experimental approaches through both laboratory (principally using wind/water tunnels) and field measurements are summarised. Finally, we present what seems to us to be the best current synthesis of the wind tunnel and field results for the prediction of gas exchange rates across the sea surface.
A coupled, one-dimensional ecosystem/carbon flux model is used to simulate the seasonal and interannual variability of phytoplankton, nutrients, TCO2, O2, and pCO2 at ocean weather station Papa (OWS P at 50°N, 145°W). The 23-year interannual simulation (1958-1980) is validated with available data and analyzed to extend seasonal and interannual variations beyond the limited observational records. The seasonal cycles of pCO2 and sea-air CO2 flux are controlled by a combination of thermodynamics, winds, and biological uptake. There is ingassing of CO2 during the fall-winter months when SSTs are colder and wind forcing is vigorous, while there is a much smaller ingassing of CO2 during the summer when sea surface temperatures are warmer and wind speeds are reduced. Biological production plays a major role in maintaining the air-sea equilibrium. An abiotic simulation showed that OWS P would be a source of atmospheric CO2 (1.41 molCm-2yr-1) if the biological sink of CO2 were removed. The peak net community production in summer compensates for the increased temperature effect on pCO2, which prevents large outgassing in summer. Oxygen anomalies relative to the temperature-determined saturation value show that there is a seasonal cycle of air-sea flux, with ingassing in winter and outgassing in summer. The net surface oxygen flux is positive (0.8 molm-2yr-1), indicating that OWS P is a source of oxygen to the atmosphere. The average primary production is 167 gCm-2yr-1. The 1960-1980 (1958 and 1959 spin-up years removed) mean carbon flux is ~1.8 molCm-2yr-1, indicating that the ocean at OWS P is a sink of atmospheric carbon. The sea-air CO2 flux ranges from -1.2 to -2.3 molCm-2yr-1 during the 21-year simulation period. This finding emphasizes the need for long-term observations to accurately determine carbon flux budgets. A series of sensitivity experiments indicate that the seasonal variability and overall (21 years) mean of TCO2, pCO2, DeltapCO2, and air-sea CO2 flux are strongly dependent on the gas transfer formulation adopted, the total alkalinity near the surface, and the bottom (350 m) value adopted for TCO2. The secular atmospheric pCO2 upward trend is manifested in the TCO2 concentration within the upper 100 m by an increase of 15 mmolm-3 in 20 years, consistent with observations at other locations [Winn et al., 1998; Bates, 2001].
A pelagic food web model was formulated with the goal of developing a quantitative understanding of the relationship between total production, export production, and environmental variables in marine ecosystems. The model assumes that primary production is partitioned through both large and small phytoplankton and that the food web adjusts to changes in the rate of allochthonous nutrient inputs in a way that maximizes stability, i.e., the ability of the system to return to steady state following a perturbation. The results of the modeling exercise indicate that ef ratios, defined as new production/totalproduction=exportproduction/totalproduction, are relatively insensitive to total production rates at temperatures greater than ~25°C and lie in the range 0.1-0.2. At moderate to high total production rates, ef ratios are insensitive to total production and negatively correlated with temperature. The maximum ef ratios are ~0.67 at high rates of production and temperatures of 0°-10°C. At temperatures less than ~20°C, there is a transition from low ef ratios to relatively high ef ratios as total production increases from low to moderate values. This transition accounts for the hyperbolic relationship often presumed to exist between ef ratios and total production. At low rates of production the model predicts a negative correlation between production and ef ratios, a result consistent with data collected at station ALOHA (22°45'N, 158°W) in the North Pacific subtropical gyre. The predictions of the model are in excellent agreement with results reported from the Joint global Ocean Flux Study (JGOFS) and from other field work. In these studies, there is virtually no correlation between total production and ef ratios, but temperature alone accounts for 86% of the variance in the ef ratios. Model predictions of the absolute and relative abundance of autotrophic and heterotrophic microorganisms are in excellent agreement with data reported from field studies. Combining the ef ratio model with estimates of ocean temperature and photosynthetic rates derived from satellite data indicates that export production on a global scale is ~20% of net photosynthesis. The results of the model have important implications for the impact of climate change on export production, particularly with respect to temperature effects.
The 14CO2 released into the stratosphere during bomb testing in the early 1960s provides a global constraint on air-sea gas exchange of soluble atmospheric gases like CO2. Using the most complete database of dissolved inorganic radiocarbon, DI14C, available to date and a suite of ocean general circulation models in an inverse mode we recalculate the ocean inventory of bomb-produced DI14C in the global ocean and confirm that there is a 25% decrease from previous estimates using older DI14C data sets. Additionally, we find a 33% lower globally averaged gas transfer velocity for CO2 compared to previous estimates (Wanninkhof, 1992) using the NCEP/NCAR Reanalysis 1 1954-2000 where the global mean winds are 6.9 m s-1. Unlike some earlier ocean radiocarbon studies, the implied gas transfer velocity finally closes the gap between small-scale deliberate tracer studies and global-scale estimates. Additionally, the total inventory of bomb-produced radiocarbon in the ocean is now in agreement with global budgets based on radiocarbon measurements made in the stratosphere and troposphere. Using the implied relationship between wind speed and gas transfer velocity k s = 0.27$\langle$ u 10 2 $\rangle$(Sc/660)-0.5 and standard partial pressure difference climatology of CO2 we obtain an net air-sea flux estimate of 1.3 +/- 0.5 PgCyr-1 for 1995. After accounting for the carbon transferred from rivers to the deep ocean, our estimate of oceanic uptake (1.8 +/- 0.5 PgCyr-1) compares well with estimates based on ocean inventories, ocean transport inversions using ocean concentration data, and model simulations.
Estimates of phytoplankton sticking efficiency (α) were made in the laboratory within a 1500 l annular flume meso- cosm over the initiation, maintenance and senescence phases of a bloom of the diatom Thalassiosira pseudonana. The spatially weighted mean turbulence kinetic energy dissipation rate in the annular flume was comparable to values found at the ocean's sur- face on a calm day. The α of T. pseudonana varied as a result of physiological state, and ranged from 0 ± 0.08 during the bloom ini- tiation to 0.26 and 0.73 ± 0.16, respectively, during bloom mainte- nance and senescence phases. During the periods of high α, physiological changes included (1) diminished phytoplankton photosynthetic quantum efficiency, (2) an increase in super-oxide dismutase protein expression, reflecting oxidative stress, and (3) the induction of a biochemical cascade initiating autocatalytic pro- grammed cell death. Additionally, during the period of high physi- ological stress on the diatoms, there was an increase in the pres- ence of transparent exopolymer particles and bacteria. Applying a variable α to a 1-dimensional export flux model shows that carbon export can be increased by at least 2-fold compared to simulations assuming a typically modeled value of α = 1 (100% sticking effi- ciency). The model using a physiologically dependent α had a low initial sticking efficiency that allowed a significant increase in the critical concentration of algal cells. Such an increase in the number of cells during bloom initiation followed by an increase in α during the maintenance and senescence phases resulted in enhanced export fluxes during the latter, 'stickier', stages of the bloom.
Measurements of air-sea gas exchange rates are reported from two deliberate tracer experiments in the southern North Sea during February 1992 and 1993. A conservative tracer, spores of the bacterium Bacillus globigii var. Niger, was used for the first time in an in situ air-sea gas exchange experiment. This nonvolatile tracer is used to correct for dispersive dilution of the volatile tracers and allows three estimations of the transfer velocity for the same time period. The first estimation of the power dependence of gas transfer on molecular diffusivity in the marine environment is reported. This allows the impact of bubbles on estimates of the transfer velocity derived from changes in the helium/sulphur hexafluoride ratio to be assessed. Data from earlier dual tracer experiments are reinterpreted, and findings suggest that results from all dual tracer experiments are mutually consistent. The complete data set is used to test published parameterizations of gas transfer with wind speed. A gas exchange relationship that shows a dependence on wind speed intermediate between those of Liss and Merlivat [1986] and Wanninkhof [1992] is found to be optimal. The dual tracer data are shown to be reasonably consistent with global estimates of gas exchange based on the uptake of natural and bomb-derived radiocarbon. The degree of scatter in the data when plotted against wind speed suggests that parameters not scaling with wind speed are also influencing gas exchange rates.
Approximately half of the world's net annual photosynthesis occurs in the oceans ( similar to 48 Pg C y(-1)). Areas bordering continents ( bottom < 2000 m) support 10 - 15% of this production. We used satellite data to compute annual global net primary production ( 1998 - 2001), and derived the global particulate organic carbon ( POC) flux settling below the permanent thermocline and to the seafloor using an empirical model of POC remineralization. Approximately 0.68 Pg C y(-1) sink below the thermocline on continental margins, compared to 1.01 Pg C y(-1) in the deep ocean. Over 0.62 Pg C y(-1) settles to the seafloor on margins, compared to 0.31 Pg C y(-1) to deep ocean sediments. At least 0.06 Pg C y(-1) may be buried in sediments on margins. Therefore, margins may be responsible for > 40% of the carbon sequestration in the ocean. These regions must be accounted for in realistic models of the global carbon cycle and its linkages to climate change.
High resolution surface wind fields covering the global ocean, estimated from remotely sensed wind data and ECMWF wind analyses, have been available since 2005 with a spatial resolution of 0.25° in longitude and latitude, and a temporal resolution of 6h. Their quality is investigated through various comparisons with surface wind vectors from 190 buoys moored in various oceanic basins, from research vessels and from QuikSCAT scatterometer data taken during 2005-2006. The NCEP/NCAR and NCDC blended wind products are also considered. The comparisons performed during January-December 2005 show that speeds and directions compare well to in-situ observations, including from moored buoys and ships, as well as to the remotely sensed data. The root-mean-squared differences of the wind speed and direction for the new blended wind data are lower than 2m/s and 30°, respectively. These values are similar to those estimated in the comparisons of hourly buoy measurements and QuikSCAT near real time retrievals. At global scale, it is found that the new products compare well with the wind speed and wind vector components observed by QuikSCAT. No significant dependencies on the QuikSCAT wind speed or on the oceanic region considered are evident.
Based on about 940,000 measurements of surface-water pCO2 obtained since the International Geophysical Year of 1956–59, the climatological, monthly distribution of pCO2 in the global surface waters representing mean non-El Niño conditions has been obtained with a spatial resolution of 4°×5° for a reference year 1995. The monthly and annual net sea–air CO2 flux has been computed using the NCEP/NCAR 41-year mean monthly wind speeds. An annual net uptake flux of CO2 by the global oceans has been estimated to be 2.2 (+22% or −19%) Pg C yr−1 using the (wind speed)2 dependence of the CO2 gas transfer velocity of Wanninkhof (J. Geophys. Res. 97 (1992) 7373). The errors associated with the wind-speed variation have been estimated using one standard deviation (about±2 m s−1) from the mean monthly wind speed observed over each 4°×5° pixel area of the global oceans. The new global uptake flux obtained with the Wanninkhof (wind speed)2 dependence is compared with those obtained previously using a smaller number of measurements, about 250,000 and 550,000, respectively, and are found to be consistent within±0.2 Pg C yr−1. This estimate for the global ocean uptake flux is consistent with the values of 2.0±0.6 Pg C yr−1 estimated on the basis of the observed changes in the atmospheric CO2 and oxygen concentrations during the 1990s (Nature 381 (1996) 218; Science 287 (2000) 2467). However, if the (wind speed)3 dependence of Wanninkhof and McGillis (Res. Lett. 26 (1999) 1889) is used instead, the annual ocean uptake as well as the sensitivity to wind-speed variability is increased by about 70%.
We constructed a simple non-steady-state model of trophic cycling relationships in the California Current Ecosystem and tested its predictions of mesozooplankton fecal-pellet export against vertical carbon-flux measurements by the Th-234 method taken during Lagrangian experiments. To assess trophic relationships, we simultaneously measured C-14-primary production and chlorophyll-based rate estimates of phytoplankton growth, microzooplankton grazing, mesozooplankton grazing, and net phytoplankton growth. Study locations ranged from coastal upwelling to offshore oligotrophic conditions. E-ratios (carbon export : C-14-primary production) predicted by the model ranged from 0.08 to 0.14, in good agreement with both the magnitude and the variability found in contemporaneous measurements of Th-234 export and C: Th-234-ratios of sinking particles. E-ratios were strongly decoupled from new production estimates. The lowest measured and predicted e-ratios were associated with higher nutrient chlorophyll parcels with net accumulating phytoplankton in the inshore region. For our study sites, variability in export efficiency was determined by the local net balance of growth and grazing and the relative strengths of grazing pathways to microzooplankton and mesozooplankton. Despite very different plankton assemblages studied, the consistently good agreement between independently measured production-grazing processes and biogeochemical rates suggest that zooplankton are the major drivers of vertical carbon-flux in this system during springtime.
A method is presented for the shipboard analysis of dissolved gases (O 2, CO2, Ar, N2, H2S, dimethylsulfide) in oceanic waters using membrane inlet mass spectrometry (MIMS). Gases are extracted from seawater across a semi-permeable membrane into the ion source of the mass spectrometer. The method can be used to simultaneously measure both major and trace gases in seawater samples in near real-time. In the case of DMS, low nmol L-1 detection limits can be achieved without any concentration step. Multiple calibration and method comparison exercises conducted in the subarctic Pacific Ocean show that the MIMS method provides gas measurements that are consistent with those obtained by standard techniques, with precision of replicate samples ranging from less than 1% to approximately 5% coefficient of variation (CV). To illustrate the usefulness of the MIMS approach, depth profiles are presented for O2, CO2, N2, and DMS at various coastal and open ocean stations in the subarctic Pacific. In addition to these discrete gas measurements, the MIMS system has also been used to continuously monitor gas concentrations along underway transects. High frequency gas measurements of O2, CO2, and DMS made along two coastal transects reveal a high degree of spatial and temporal variability in gas concentrations, likely resulting from the interplay of various biological, chemical, and physical forcings. The underway MIMS data provide insight into the biogeochemical controls on gas cycling in dynamic marine waters. © 2004, by the American Society of Limnology and Oceanography, Inc.
Seasonal cycles of oxygen, temperature and salinity at Ocean Weather Station P in the subarctic Pacific Ocean reveal a regular 4–6% supersaturation of oxygen in the surface waters during the summers of the 10-year period 1969–1978. The main processes causing super-saturation are surface water heating and the net effect of primary production and community respiration. The biological and heating signals are separated using a mixed layer model and estimates for the air-water gas exchange rate calculated from empirical correlations to wind speed. Biological new production during the summer (mid-May to mid-August) is estimated to be 100–300 mg C m−2 d−1. These values are within the range of independent estimates calculated from the summer nitrate depletion. There is a factor of 3 variation in the new production estimates during the period 1969–1978 with a minimum in 1973–1975. This trend is positively correlated with the interannual variation in zooplankton standing stock at station P.
The effect of temperature, biological processes, air-sea CO2
exchange and vertical mixing as drivers of the seasonality of the
surface water fugacity of CO2 (fCO2sw) were
studied for the year 2000 in the subarctic North Pacific Ocean. The
regional and seasonal variability of the surface water chemistry was
studied using an extensive data set on surface water fCO2 and
nutrient concentrations in six contrasting provinces. We observed the
largest seasonal amplitude for all parameters in the western provinces
(Oyashio and Western Subarctic Gyre, WSG). Our study showed that
biological processes and temperature were major controls for the monthly
fCO2sw change in all provinces. The magnitude and strength of
the processes showed large temporal and spatial variability. The WSG
showed larger influence by biological processes and vertical mixing than
the Alaska gyre (AG), where the effect caused by temperature was larger,
implying different forcing of the fCO2 change in the two
gyres. Biological activity, estimated from the monthly nitrate change
corrected for addition induced by vertical mixing, resulted in a net
annual CO2 loss. The net carbon loss out of the top 50 m
driven by biological activity was 3 times higher in the WSG (64 g C
m-2 yr-1) than in the AG (23 g C m-2
yr-1). The annual sum of the fCO2sw change based
on all processes resulted in a CO2 buildup in the surface
waters for all provinces. Although the air-sea CO2 exchange
was of minor importance relative to the other considered processes (4 to
13%), all provinces showed a net annual uptake of atmospheric
CO2 from 1 to 23 g C m-2 yr-1 and an
average for the whole study area of about 12 (±9) g C
m-2 yr-1.
Net community biological production in the euphotic zone of the ocean fuels organic matter and oxygen export from the upper ocean, which has a large influence on the atmospheric pressure of carbon dioxide and is the driving force for metabolite distributions in the sea. We determine the net annual biological oxygen production in the mixed layer of the northeast subarctic Pacific Ocean from in situ O2 and N2 measurements. Temperature, salinity, total gas pressure and O2 were measured every 3 h for 9 months in 2007 at about 3 m depth on a surface mooring at Station P (50°N, 145°W). The concentration of nitrogen gas, N2, determined from separate total gas pressure and pO2 measurements, was used as an inert tracer of the physical processes that induce gas departure from thermodynamic equilibrium with the atmosphere. We use a simple model of the ocean’s mixed layer along with the nitrogen concentration to constrain the importance of bubbles, gas exchange and horizontal advection, which are then used in the oxygen mass balance to derive net biological oxygen production. The mixed-layer oxygen mass balance is dominated by exchange with the atmosphere, and we determine a mean summertime oxygen production of 24 mmol O2 m−2 d−1. The annual pattern in the difference between the supersaturation of oxygen and nitrogen in the surface waters reveals very little net oxygen production during the winter at this location. The calculated annual net community production (NCP) of carbon from this new method, 2.5 mol m−2 yr−1, agrees to within its error of about×40% with previous determinations at this location from oxygen mass balance, NO3− draw down and 234Th measurements. This value is either indistinguishable from or lower than annual NCP measurements in the subtropical North Pacific, indicating that there is no experimental evidence for differences in annual NCP between the subarctic and subtropical North Pacific Ocean.
Diffusion coefficients for dissolved hydrogen, oxygen, nitrogen, air, helium, argon, methane, ethane proprane and n-butane have been measured in water at 10°, 20°, 30°, 40°, 50° and 60°C by following the rate of collapse of small bubbles in gas-free water, the results being compared wherever possible with corresponding diffusivities published in the literature. The temperature dependence of the diffusion coefficients is expressed in terms of an Arrhenius-type exponential relationship, the frequency factor and activation energy for dissolved gas diffusion in water being interpreted in terms of the hole mechanism of activated self diffusion originally proposed by Eyring. The solute gas diffusivities in water are also compared with those predicted theoretically from solvent viscosity by the relationships of Einstein, Eyring, Longuet-Higgins and Pople, Ree, Ree and Eyring, and Houghton, the purpose being to find a physical explanation for the observed variation of diffusion coefficient with solute molecule size.
The relationship between flow cytometric fluorescence signals and photosynthetic pigments was investigated in three species of marine eucaryotic phytoplankton, ThaZassiosiru weissflogii, Hy- menomonas carterae, and Amphidinium carteri. The species were grown over a range of light intensities to provide a spectrum of pigment compositions for the study. Both interspecific and intraspecific differences were observed. Variations among the species in fluorescence per unit of chlorophyll a (Chl a) could be explained by differences in the relative abundance of Chl a and accessory pigments. Amphidinium carteri had much greater fluorescence per unit of Chl a than the other two species and it had the highest Chl c : Chl a ratio. Fluorescence per unit of Chl a decreased as Chl a per cell increased in H. carterae and A. carteri, whereas it remained the same in T. weissflogii. We interpret these differences to have their origins in the "package" effect on light absorption. This effect seems to be least evident in the diatom because cell size increased as Chl a per cell increased in low-light-grown cells. In H. carterae and A. carteri the opposite was true, such that the intracellular concentration of Chl a increased substantially in the low-light cells. Based on these data, we find that to interpret fluorescence signals among species, differences in the relative abundances of Chl a and accessory pigments must be considered, while for intraspecific fluorescence differences, the package effect may be more important.
A two-year study of the iron distributions in anticyclonic mesoscale Haida eddies of the eastern North Pacific Ocean has shown that such eddies are a major source of iron to the high nitrate–low chlorophyll (HNLC) waters of the central Gulf of Alaska basin. These eddies, which are typically about 100km in diameter, form off the west coast of Canada in winter and then track roughly westward into the open ocean. Therefore, they carry large quantities of iron-rich coastal waters into iron-limited waters of the oligotrophic gyre. When the eddies had first formed, their dissolved iron concentrations were nearly two orders of magnitude higher than is typically observed at Station Papa (50°N, 145°W; 3nm versus less than 0.05nm), and the total iron in the eddies surface waters (10–40m) was more than 13nm higher than open ocean waters of the Alaska gyre (14nm versus 0.5nm). While the overall iron content of the eddies decreased rapidly during the first year after they formed, the eddy we were able to track the longest still contained 1.5–2 times more iron than the surrounding waters 16 months after its formation. Therefore, although iron concentrations in the surface mixed layers of the eddies drop to levels observed outside very rapidly (within 4 months), upward transport along isopycnals and upwelling due to eddy decay, as well as vertical advective and diffusive transports typical of North Pacific waters, probably provide steady fluxes of iron into the euphotic zone from the still iron-rich eddy core waters throughout the lifetime of the eddy.
Mesoscale anticyclonic eddies in the Gulf of Alaska are an important mechanism for cross-shelf exchange of high iron, low nitrate coastal waters and low iron, high nitrate offshore waters. A Kenai eddy was sampled in September 2007, 8 months after formation. The subsurface eddy core layer contained reactive iron concentrations more than eight times greater than waters at the same depths outside the eddy. The subsurface core of the Kenai eddy (25.4≤σθ≤25.8) is suggested to be seasonally important as these waters can be brought to the surface with storm events and deep winter mixing. The deeper core layer (25.8≤σθ≤27.0) is suggested to be a source of iron to HNLC waters on a longer timescale, due to isopycnal mixing and eventual eddy relaxation. The subsurface and deeper core layers are important reservoirs of iron that can promote and sustain primary productivity over the lifetime of the Kenai eddy. In addition, dissolved and leachable particulate manganese are shown to be excellent tracers of eddy surface and subsurface waters, respectively.
Distributions of oxygen, argon, nitrogen, and radon in the upper ocean of the subarctic Pacific distinguish the fluxes controlling the oxygen mass balance during the summers of 1987 and 1988. The difference between the net O2 flux (in mmol m−2 d−1) to the atmosphere via gas exchange (32) and the integrated decrease with time (−14) is balanced by biological production (13-17), air injection by bubble entrainment (5), and O2 flux to the thermocline −(0-4). Nitrogen/argon and oxygen/argon ratios reveal that ˜15% of the oxygen supersaturation in summer is produced by air injection and ˜40% by biological production, with the rest induced by surface water warming. Our estimate of biologically induced oxygen production when translated stoichiometrically to nitrogen uptake agrees to within error estimates with both the particulate and dissolved nitrogen mass balances for the upper ocean determined in the SUPER program during the same time period. The oxygen mass balance requires a net carbon production in the euphotic zone of ˜140 mg C m−2 d−1 (PQ=1.5), which is 20–30% of the level of 14C primary production determined by SUPER investigators.
We measured gross primary productivity (GPP) in vitro and GPP and net community production (NCP) in situ on four cruises to the Hawaii Ocean Time series (HOT) station ALOHA during 2002–2003. In vitro GPP, determined by 18O labeling, yielded integrated production (0–100 m) that was on average 1.5 times the 14C integrated production. Mean integrated productivity from two winter and two summer cruises was 575 mg C m−2d−1 and 930 mg C m−2d−1, respectively. In situ GPP, determined from the triple-isotope composition of dissolved O2, averaged 910 mg C m−2d−1 in the winter and 1225 mg C m−2d−1 in the summer/fall, with an uncertainty of ±40%. The NCP/GPP ratio, determined using O2/Ar gas ratio and oxygen isotope measurements, was around 0.1 in the summer, close to the canonical f-ratio for the open ocean, indicating station ALOHA is a net autotrophic system during summer months. The consistently higher gross carbon production measured by the in situ method, which integrates production over the ∼2-week residence time of O2 in the mixed layer, suggests that aperiodic bursts of production contribute significantly to time-averaged mean productivity at station ALOHA.
Particle fluxes measured with time series sediment traps deployed below 2000 m at 68 sites in the world ocean are combined with satellite-derived estimates of export production from the overlying water to assess the factors affecting the transfer of particulate organic matter from surface to deep water. Multiple linear regression is used to derive an algorithm suggesting that the transfer efficiency of organic carbon, defined as the settling flux of organic carbon normalized to export production, increases with the flux of carbonate and decreases with water depth and seasonality. The algorithm predicts >80% of the organic carbon transfer efficiency variability in diverse oceanic regions. The influence of the carbonate flux suggests that the ballasting effect of this biogenic mineral may be an important factor promoting export of organic carbon to the deep sea by increasing the density of settling particles. However, the lack of a similar effect for biogenic opal suggests that factors other than particle density also play a role. The adverse effect of increasing seasonality on the transfer efficiency of carbon to the deep sea is tentatively attributed to greater biodegradability of organic matter exported during bloom events. In high latitude opal-dominated regions with high f-ratios and seasonality, while a higher fraction of net production is exported, a higher fraction of the exported organic matter is remineralized before reaching bathypelagic depths. On the other hand, in warm, low latitude, carbonate-dominated regions with low f-ratios and seasonality, a higher fraction of the exported organic matter sinks to the deep sea.
Estimates of mixed layer depth are important to a wide variety of oceanic investigations including upper-ocean productivity, air-sea exchange processes, and long-term climate change. In the absence of direct turbulent dissipation measurements, mixed layer depth is commonly derived from oceanic profile data using threshold, integral, least squares regression, or other proxy variables. The different methodologies often yield different values for mixed layer depth. In this paper, a new method-the split-and-merge (SM) method-is introduced for determining the depth of the surface mixed layer and associated upper-ocean structure from digital conductivity-temperature-depth (CTD) profiles. Two decades of CTD observations for the continental margin of British Columbia are used to validate the SM method and to examine differences in mixed layer depth estimates for the various computational techniques. On a profile-by-profile basis, close agreement is found between the SM and de facto standard threshold methods. However, depth estimates from these two methods can differ significantly from those obtained using the integral and least squares regression methods. The SM and threshold methods are found to approximate the "true" mixed layer depth whereas the integral and regression methods typically compute the depth of the underlying pycnocline. On a statistical basis, the marginally smaller standard errors for spatially averaged mixed layer depths for the SM method suggest a slight improvement in depth determination over threshold methods. This improvement, combined with the added ability of the SM method to delineate simultaneously ancillary features of the upper ocean (such as the depth and gradient of the permanent pycnocline), make it a valuable computational tool for characterizing the structure of the upper ocean.
Twenty-four near-exact repeat tracks (over a 48-month period) of ocean
surface pCO2 data from the North Pacific offer an
uprecedented opportunity to examine the space scales of pCO2
in this region. Because previous basin scale studies of air-sea carbon
flux have shown that the field Of ΔpCO2 (air-sea
disequilibrium) largely controls the field of flux (and atmospheric
pCO2 is relatively constant), knowing how to sample
pCO2 in seawater is a crucial element of the design of a
basin scale carbon flux observing system. Unbiased (within 3 µatm)
along-track means for ΔpCO2 can be obtained from
measurements made every 40 km (∼ hourly for a ship traveling 20
knots). We find distinctly different characteristics of spatial
variability in two open ocean regions, the Bering Sea and the Gulf of
Alaska. The first zero crossing of the mean spatial autocorrelation
function is 1.5° longitude in the Bering Sea and 3.5° in the
Gulf of Alaska, when the cruise data are linearly detrended to remove
the larger scale field. There is a strong seasonal variation in the zero
crossing, with shorter scales in the summer. In near-shore waters there
is extreme variability, often with very small space scales and very
large cruise-to-cruise differences. Neither the mean nor variability
statistics from a single ship cruise data set appear likely to produce
reliable information for designing an observing system.
We determine annual rates of net biological oxygen production in the euphotic zone and respiration in the upper thermocline of the subtropical North Pacific ocean using mass balances of oxygen, argon, and nitrogen measured at the U.S. Joint Global Ocean Flux Study time series station ALOHA. Net evasion of nitrogen and argon to the atmosphere caused by warming of surface waters is balanced by supply primarily from cross-isopycnal transport. Mixing rates between the euphotic zone and the top of the permanent thermocline required to balance the inert gas flux are 1-2 cm2s-1 when transformed to units of an eddy diffusion coefficient. Application of mixing rates derived from the inert gas mass balance to the oxygen field yields at a net annual euphotic zone production rate of 1.4+/-1.0 moles O2 m-2yr-1, one half of which is lost to the atmosphere, with most of the rest mixed into the top of the thermocline. Since cross-isopycnal gradients of dissolved organic carbon (DOC) are about half to those of oxygen, we estimate that at least one quarter of the carbon flux out of the euphotic zone is via DOC. Because surface ocean dissolved organic matter has a relatively high C/N ratio, the stoichiometry among O2, C and inorganic N in the upper ocean should be different than that observed in deeper waters.
Monthly distribution maps of ΔpCO2 (oceanic pCO2 minus atmospheric pCO2) in the northern North Pacific were constructed based on observations from a commercial vessel in March 1995–1999. These maps clearly show the seasonal progression of ΔpCO2 for the entire region. The results were compared with those of Takahashi et al. (Proc. Natl. Acad. Sci., USA 94 (1997) 8292), who derived global ΔpCO2 distributions using a different data set and method of interpolation. The annual mean difference between the two sets of ΔpCO2 is 3μatm, much smaller than the annual mean ΔpCO2 of −14μatm obtained by this study. However, monthly mean differences can be as large as the annual mean ΔpCO2, and the monthly difference in individual 4°×5° boxes can be as large as 70μatm. There is no grid box that shows consistently large or small differences throughout the year. We also compared CO2 fluxes estimated from the two different sets of ΔpCO2 but the same set of wind, sea-surface temperature and salinity. Both studies find that the northern North Pacific is a small sink for carbon (−0.26GtCyr−1, this study; and −0.33GtCyr−1, Takahashi et al., 1997). Monthly fluxes based on the two data sets show larger differences, especially in spring and autumn. Further observations will help to reduce the difference in calculating monthly ΔpCO2 distributions by different interpolation algorithms and, therefore, improving the estimation of CO2 fluxes in the northern North Pacific.
Profiles of particulate and dissolved 234Th (t1/2=24.1d) were collected during the Canadian JGOFS program (February, May, and August 1996 and February 1997) along a transect from 125°W to 145°W at 50°N (Ocean Station Papa – OSP). Persistent features included a deficit of 234Th relative to its parent 238U in the upper ∼75m and occasionally an excess of total 234Th (particulate+dissolved) at ∼150–200m attributed to redissolution of the particulate-bound nuclide. To calculate POC export fluxes, a steady-state model of 234Th export was combined with measurements of the POC/234Th ratio determined on particles >1-μm collected by in situ filtration. Along the transect, e-ratios (POC export/primary production) calculated for the 0.1% light level were similar during February 1997 and May 1996, 0.06–0.08 (avg. POC flux =2.8–7.1mmolCm−2d−1). During August 1996, e-ratios reached a maximum, averaging 0.13 (avg. POC flux=7.6mmolCm−2d−1). Particulate 234Th fluxes measured by drifting cylindrical sediment traps were 3-fold greater than the flux calculated for the water column 234Th deficit. Finally, to study changes in 234Th and POC export on short time-scales, some stations were sampled twice within 36hours. During February 1997, 234Th increased nearly 50% from 60–100m in a 36 h period. Hydrographic data suggest that this change was due to advective processes.
The subarctic North Pacific is one of the three major high nitrate low chlorophyll (HNLC) regions of the world. The two gyres, the NE and the NW subarctic Pacific gyres dominate this region; the NE subarctic Pacific gyre is also known as the Alaska Gyre. The NE subarctic Pacific has one of the longest time series of any open ocean station, primarily as a result of the biological sampling that began in 1956 on the weathership stationed at Stn P (50°N, 145°W; also known as Ocean Station Papa (OSP)). Sampling along Line P, a transect from the coast (south end of Vancouver Island) out to Stn P has provided valuable information on how various parameters change along this coastal to open ocean gradient. The NW subarctic Pacific gyre has been less well studied than the NE gyre. This review focuses mainly on the NE gyre because of the large and long term data set available, but makes a brief comparison with the NW gyre. The NE gyre has saturating NO3 concentrations all year (winter = about 16 μM and summer = about 8 μM), constantly very low chlorophyll (chl) (usually
In the subarctic Pacific and its adjacent waters, the photochemical quantum yield (Fv/Fm) and the functional absorption cross section (sPSII ) of photosystem II for surface phytoplankton were continuously measured during the early summer of 1999 using a fast repetition rate fluorometer. Concentrations of total dissolvable iron (TD-Fe) were also determined at each sampling station. The maximum value (0.61) of Fv/Fm was observed off the Aleutian Peninsula, where TD-Fe concentrations were relatively high. The Western Subarctic Gyre (WSG) and the Alaskan Gyre (AG), located in the northwest and northeast subarctic Pacific, respectively, were in high-nutrient, low-chlo- rophyll (HNLC) conditions. Surface TD-Fe generally remained in the WSG but was depleted (,0.01 nmol L 21 )i n the AG. Nighttime Fv/Fm and sPSII in the WSG were significantly higher (p , 0.01) and lower (p , 0.01), respectively, than in the AG. Iron or nitrogen limitations generally lead to a decrease in Fv/Fm and an increase in sPSII. These results suggested that there was an east-west gradient (WSG . AG) in the photosynthetic competence of phytoplankton in the subarctic Pacific and that the difference was probably caused by iron levels in seawater. Indeed, our iron enrichment experiment in the AG revealed that Fv/Fm increased from 0.27 to 0.49 and sPSII decreased from 496 3 10 220 to 365 3 10 220 m 2 photon 21 after a 0.8 nmol L 21 iron addition. At the same time, a dramatic floristic shift from phytoflagellates to diatoms was found by pigment signatures. Iron could principally control the photosynthetic physiology of phytoplankton in the whole subarctic Pacific. The identification of factors controlling primary produc- tion is a key issue for a better understanding of the biogeo- chemical processes in high-nutrient, low-chlorophyll (HNLC) regions, where macronutrients (nitrate, phosphate, and silicate) are abundant and where phytoplankton stocks 1
The coastal Gulf of Alaska (CGOA) supports high abundances of invertebrates, fishes, and marine mammals. While variable from year to year, multi-decade fish production trends have been correlated with climate regimes such as the Pacific Decadal Oscillation. Winds, massive freshwater inputs, and complex topography in the CGOA create high-energy physical features on multiple time and space scales. This suggests that climate might be linked to higher trophic level production through the regulation of resources for primary producers. Data from spring and summer 2001 revealed seasonal and spatial variability in the factors regulating CGOA primary production. Some of the highest growth rates (> 1.0 d(-1), as estimated with the seawater dilution technique) were measured in April diatom blooms. Nitrogen limitation of growth rates was evident as early as late April and appeared to follow closely the onset of spring stratification. The summer phytoplankton community was dominated by small (< 5 mu m) cells exhibiting varying degrees of nitrogen limitation depending on cross-shelf location. However,we observed an intense mid-summer diatom bloom in the Alaska Coastal Current, perhaps a response to a series of upwelling events. Strong cross-shelf gradients governed every aspect of phytoplankton community structure and function, including overall biomass, cell size, species composition, nutrient utilization, growth rate, and degree of macronutrient limitation. These gradients were consistent with a cross-shelf gradient in dissolved iron availability. Because the type of resource limitation and the taxonomic composition of the phytoplankton community varied across the shelf, a stepwise regression of whole-shelf phytoplankton growth rates versus resource availability had little predictive power. The effect of climate-driven resource variation on primary production in the CGOA has to be understood in the context of different community types, their production potential, and the environmental conditions that dictate their extent and stability.
Autotrophic and microheterotrophic plankton populations were monitored in the euphotic zone of the eastern subarctic Pacific during 6 one-month cruises in spring and summer, 1984, 1987 and 1988. Transmitted light, epifluorescence, and electron microscopy were used to identify, enumerate and estimate the biomass of size-populations of species. The 2–10μm size class dominated the biomass of both autotrophs and heterotrophs. The autotrophic flagellate, Phaeocystis pouchetii, was frequently observed in its non-colonial phase. Temporal variation in all the stocks was evident and could be explained only partially by the physical, chemical or biological factors investigated here. The general structure of the autotrophic community was similar to that in the North Atlantic, but major, unexplained variations between cruises occurred. Variation in mixed-layer depth and day length (but not variation in daily insolation) explained 25% of the variation in autotrophic doubling rate. Heterotrophic biomass comprised, in decreasing order of importance, non-pigmented flagellates, dinoflagellates, and ciliates. Ciliates rarely contributed more than 40% to the total. Microheterotrophic biomass rarely exceeded 30μg C 1−1 (avg 15μg C 1−1, 0–60m) whereas autotrophic biomass averaged 20μg C 1−1, 0–60m, and reached 74μg C 1−1 on one occasion, yet the grazing capacity of these microheterotrophs averaged 100% of primary production.
The northern Gulf of Alaska shelf is a productive coastal region that supports several commercially important fisheries. The mechanisms supporting such high levels of productivity over this shelf, however, are not understood since it is a downwelling-dominated shelf. Furthermore, the annual nutrient cycle in this region was completely unknown prior to this research. In an effort to understand the mechanisms driving such high biological productivity, cross-shelf nutrient distributions were sampled 18 times throughout 1998, 1999 and 2000. Deep-water (>75 m) nitrate, silicate and phosphate were positively correlated with salinity, indicating an offshore nutrient source. The average annual cycle was established, in which nitrate, silicate and phosphate responded seasonally to physical and biological processes. Ammonium concentrations were generally low and uniform (
Coastal upwelling events in the California Current System can transport subsurface waters with high levels of carbon dioxide (CO2) to the sea surface near shore. As these waters age and are advected offshore, CO2 levels decrease dramatically, falling well below the atmospheric concentration beyond the continental shelf break. In May 2007 we observed an upwelling event off the coast of northern California. During the upwelling event subsurface respiration along the upwelling path added ∼35μmolkg−1 of dissolved inorganic carbon (DIC) to the water as it transited toward shore causing the waters to become undersaturated with respect to Aragonite. Within the mixed layer, pCO2 levels were reduced by the biological uptake of DIC (up to 70%), gas exchange (up to 44%), and the addition of total alkalinity through CaCO3 dissolution in the undersaturated waters (up to 23%). The percentage contribution of each of these processes was dependent on distance from shore. At the time of measurement, a phytoplankton bloom was just beginning to develop over the continental shelf. A box model was used to project the evolution of the water chemistry as the bloom developed. The biological utilization of available nitrate resulted in a DIC decrease of ∼200μmolkg−1, sea surface pCO2 near ∼200ppm, and an aragonite saturation state of ∼3. These results suggest that respiration processes along the upwelling path generally increase the acidification of the waters that are being upwelled, but once the waters reach the surface biological productivity and gas exchange reduce that acidification over time.
Examines uncertainties associated with the routine computation of O2 solubility (Co*) at 1 atm total pressure in pure water and seawater in equilibrium with air as a function of temperature and salinity. The authors propose formulae expressing Co* (at STP, real gas) in cm3 dm-3 and μmol kg-1 in the range (tF ≥ t ≥ 40°C; 0 ≥ S ≥ 42‰) based on a fit to precise data selected from the literature. -Authors
The size of 30 small (2-60 pm) phytoplankton species was examined with a microscope and a Coulter Counter before and after fixation. Acid Lugol's iodine caused cells to shrink immediately. The shrinkage effect was constant for concentrations of l-10% Lugol's iodine (in seawater). For optically measured cells fixed in 2% Lugol's iodine, volume of live cells = 1.33 x (volume of fixed cells). Coulter Counter and optically measured volumes did not agree. For live cells, optical cell volume = 1.24-2.04 x (Coulter Counter determined volume); this difference is likely due to inaccurate volume measurements of non- spherical cells by the Coulter Counter and by inaccurate microscopy resulting from optical distortions (errors of ~0.5 pm in cell dimensions). Cell quota estimates were presented following the relation y = a.x?, where x = optically measured cell volume (pm3), y = any cell constituent (pg cell-'), and a and b are constants. The constants a and b were 0.109 and 0.99 1 for carbon, 0.0172 and 1.023 for nitrogen, 0.043 and 1.058 for protein, and 0.00428 and 0.9 17 for Chl a. Our relation of carbon to volume differs from other literature values, in which there is no consensus. Our data can be used to determine carbon, nitrogen, protein, and Chl a estimates from field material that has been fixed with Lugol's iodine, observed live, optically measured, or Coulter Counter measured; however, the variability in published data suggests that any of these estimates will have a large potential error.
The carbonate, soft tissue, and solubility 'pump' processes by which the
steady state distribution of CO2 at the ocean surface is depleted
relative to that at depth are treated. While the first two result from
the biological flux of organic and CaCO3 detritus at the ocean's
surface, the third is due to the increased CO2 solubility in downwelling
cold water. Using alkalinity, nitrate, and steady state CO2 to remove
the carbonate pump signal from ocean or model data, the individual
working strengths of the soft tissue and solubility pumps can be
calculated by an upscaling of soft tissue's Delta-CO2 distribution to
the surface-to-deep Delta-PO4. Analysis of global ocean data indicates a
positive solubility pump signal.
A process study is conducted on the evolution of boundary currents in a two-layer quasigeostrophic model on the f plane. These currents are composed of two strips of uniform potential vorticity (PV), one in each layer, and both hugging the coast. Coastal water separation (“detrainment”) through baroclinic instability and topographic perturbation is examined. It is shown that the key characteristics of the flow finite-amplitude destabilization can be explained with the help of a linear quantity—the critical amplitude Ac—that refers to the location of the line (often called critical layer) where the phase speed of the growing perturbation is equal to the unperturbed flow velocity. Notably, prediction on PV front breaking location is made possible. Different detrainment regimes (i.e., the way fragments of the boundary current are isolated and detached from the initially rectilinear core—e.g., filament formation, eddy shedding) are also identified, related to various Ac value ranges, and compared with observed oceanic events.
Large discrepancies in published neon and nitrogen solubility data limit the interpretation of oceanic measurements of these gases. We present new solubility measurements for neon, nitrogen and argon in distilled water and seawater, over a temperature range of 1-30 � C: Water was equilibrated with air at measured temperatures, salinities and pressures. Dissolved Ne concentrations were then determined by isotope dilution using a quadrupole mass spectrometer. Ratios of O2=N2=Ar were measured ona stable isotope ratio mass spectrometer, from which absolute N 2 and Ar concentrations were calculated using published O2 solubilities. We propose new equations, fitted to the data, for the equilibrium concentrations of Ne, N2 and Ar with estimated errors of 0.30%, 0.14% and 0.13%, respectively. The Ar results matched those of most previous researchers within0.4%. However, the Ne and N 2 results were greater by 1% or more thanthose of Weiss (J. Chem. En g. Data 16(2) (1971b) 235, Deep-Sea Res. 17(4) (1970) 721). r 2004 Elsevier Ltd. All rights reserved.
An interesting oceanographic problem concerns the excess major plant nutrients (PO4, NO3, SiO3) occurring in offshore surface waters of the Antarctic1–3 and north-east Pacific subarctic Oceans4. In a previous study5, we presented indirect evidence suggesting that inadequate Fe input was responsible for this limitation of growth; recently we had the opportunity to seek direct evidence for this hypothesis in the north-east Pacific subarctic. We report here that the addition of nmol amounts of dissolved iron resulted in the nearly complete utilization of excess NO3, whereas in the controls—without added Fe—only 25% of the available NO3 was used. We also observed that the amounts of chlorophyll in the phytoplankton increased in proportion to the Fe added. We conclude that Fe deficiency is limiting phytoplankton growth in these major-nutrient-rich waters.
New measurements of the solubility of carbon dioxide in water and seawater confirm the accuracy of the measurements of Murray and Riley, as opposed to those of Li and Tsui. Corrections for non-ideal behavior in the gas phase and for dissociation in distilled water are required to calculate solubility coefficients from these sets of data. Equations for the solubilities of real gases are presented and discussed. Solubility coefficients for carbon dioxide in water and seawater are calculated for the data of Murray and Riley, and are fitted to equations in temperature and salinity of the form used previously to fit the solubilities of other gases.
