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Louanchi, F., Boudjakdji, M, and Nacef, L. 2009. Decadal changes in surface carbon dioxide and related variables in the Mediterranean Sea as inferred from a coupled data-diagnostic model approach. – ICES Journal of Marine Science, 66: 1538–1546.
A coupled approach based on available datasets of temperature, salinity, oxygen, nutrients, and chloroph...
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... analysis helps to establish whether these zones are effectively different from each other in terms of hydrological variability. The results of this analysis allowed us to identify 18 independent zones (Figure 1). This grid is used for subsequent binning of the data and in applying the box model. ...
Citations
... Nutrients replenishment occurs seasonally with winter-time deep convection and allows the occurrence of intense biological processes [e.g., Beǵovic and Copin-Monteǵut, 2002;. In situ measurements of air-sea CO 2 fluxes highlighted a gradual change of the area from a source to a sink between summertime and wintertime, respectively [Beǵovic and Copin-Monteǵut, 2002;Copin-Monteǵut et al., 2004;Louanchi et al., 2009]. Moreover, a recent synthesis of the carbonate system data recorded in the Ligurian Sea between 1998 and 2016 reported both clear seasonal cycles and temporal trends for sub-surface waters [Coppola et al., 2020]. ...
Sustained time-series measurements are crucial to understand changes in oceanic carbonate chemistry. In the North Western Mediterranean Sea, the temporal evolution of the carbonate system is here investigated based on two 10-year time-series (between January 2010 and December 2019) of monthly carbonate parameters measurements at two sampling sites in the Ligurian Sea (ANTARES and DYFAMED). At seasonal timescale, the seawater partial pressure of CO2 (pCO2) within the mixed layer is mostly driven by temperature at both sites, and biological processes as stated by the observed relationships between total inorganic carbon (C T), nitrate and temperature. This study suggests also that mixing and water masses advection could play a role in modulating the CT content. At decadal timescale, significant changes in ocean chemistry are observed with increasing trends in C T (+3.2 ± 0.9 µmol.kg⁻¹.a⁻¹ – ANTARES; +1.6 ± 0.8 µmol.kg⁻¹.a⁻¹ – DYFAMED), associated with increasing pCO2 trends and decreasing trends in pH. The magnitude of the increasing trend in C T at DYFAMED is consistent with the increase in atmospheric pCO2 and the anthropogenic carbon transport of water originating from the Atlantic Ocean, while the higher trends observed at the ANTARES site could be related to the hydrological variability induced by the variability of the Northern Current.
... Bégovic and Copin-Montégut, 2002;. In situ measurements of air-sea CO 2 fluxes highlighted a gradual change of the area from a source to a sink Copin-Montégut et al., 2004;Louanchi et al., 2009]. Moreover, a recent synthesis of the carbonate system data recorded in the Ligurian Sea between 1998 and 2016 [Coppola et al., 2020a] reported both clear seasonal cycles and temporal trends for sub-surface waters. ...
... The role of the MedSea as a source or sink for atmospheric CO 2 in the global carbon cycle, especially in the context of warming MedSea waters, is unclear Vargas-Yáñez et al., 2008]. Several recent studies indicate a gradual change from a source to a sink over the last few decades [Louanchi et al., 2009;. However, in situ measurements of the carbonate seawater system are still scarce for the MedSea. ...
La mer Méditerranée est souvent considérée comme un océan laboratoire pour comprendre les changements globaux liés à l’augmentation de CO2 atmosphérique. Ce travail, basé sur l’étude de données recueilles dans trois régions méditerranéennes, étudie les variations du CO2 océanique dans ce bassin. À l’échelle de la saison, outre les changements de température, le contenu en alcalinité influe sur le contenu en CO2 en Méditerranée orientale, tandis que les changements en carbone total sont responsables des variations dans le bassin occidental. En zone côtière urbanisée, l’émission de CO2 anthropique conditionne les échanges air-mer de CO2. Cette étude montre que l’augmentation de carbone et l’acidification à l’échelle de plusieurs années ne sont pas seulement dues à l’augmentation du CO2 atmosphérique : le contenu en alcalinité module ces tendances dans le bassin oriental, tandis que, dans le bassin occidental, ces tendances sont vraisemblablement influencées par la dynamique des courants.
... Therefore, it is critical to evaluate the likely effects of climate change on the physiology and biomass productivity of this species through the simulation of anticipated future conditions. The Mediterranean Sea is recognised as a priority area for climate studies due to the previously reported increases in average seawater temperature and the occurrence of heat extremes by 200 to 500% (Diffenbaugh et al., 2007;Mieszkowska et al., 2008;Louanchi et al., 2009). ...
Short-term effects of pCO 2 (700-380 ppm; HC-LC) and nitrate content (50-5 M; HN-LC) on photosynthesis, estimated by different pulse amplitude modulated (PAMs) fluorometers and by oxygen evolution, were investigated in Ulva rigida (Chlorophyta) under solar radiation (ex-situ) and in the laboratory under artificial light (in-situ). After 6-days of incubation at ambient temperature (AT), algae were subjected to a 4 o C-temperature increase (AT+4 o C) for 3 d. Both in-situ and ex-situ, maximal electron transport rate (ETR max) and in situ gross photosynthesis (GP) measured by O 2 evolution presented the highest values under HCHN, and the lowest under HCLN, across all measuring systems. Maximal quantum yield (F v /F m), and ETR max of PSII (ETR(II) max) and of PSI (ETR(I) max), decreased under HCLN under AT+4°C. Ex situ ETR was higher than in situ ETR. At noon, F v /F m decreased (indicating photoinhibition), whereas ETR(II) max and maximal non-photochemical quenching (NPQ max) increased. ETR(II) max decreased under AT+4 o C in contrast to F v /F m , photosynthetic efficiency ( ETR) and saturated irradiance (E K). Thus, U. rigida exhibited a decrease in photosynthetic production under acidification, LN levels and AT+4 o C. These results emphasize the importance of studying the interactive effects between environmental parameters using in-situ vs. ex-situ conditions when aiming to evaluate the impact of global change on marine macroalgae. A c c e p t e d M a n u s c r i p t Abbreviations A Absorptance AT Ambient temperature ETR Electron transport rate Fv/Fm Maximal quantum yield HC High pCO 2 (700 ppm) HN High nitrate levels (50 M) LC Low pCO 2 (380 ppm) LN Low nitrate levels (5 M) NPQ Non photochemical quenching PAM Pulse amplitude modulated PAR Photosynthetic active radiation PSI Photosystem I PSII Photosystem II RLC Rapid light curves Y(II) Effective quantum yield
... ,D'Ortenzio et al. (2008), andLouanchi et al. (2009). The increasing eastward pCO 2 gradient was also observed by several researchers, in response to the increased TA and DIC concentrations (e.g.,D'Ortenzio et al., 2008;Gemayel et al., 2015;Rivaro et al., 2010;Taillandier et al., 2012). ...
Recent studies have provided a better understanding of carbonate system parameters and their spatial and temporal variability in several areas of the Mediterranean Sea. This study uses a new dataset that covered the entire Algerian Basin during the summer of 2014 (SOMBA cruise) to describe the distribution of carbonate system parameters. The findings show that almost the entire basin was a source of CO2 to the atmosphere during the studied period. Besides the well-known TrOCA (Tracer combining Oxygen, Carbon and total Alkalinity) approach, the study proposes new parametrization for the standard back calculation method to assess the anthropogenic carbon concentration. The results of both approaches yield similar distributions and concentration ranges (81 ± 4.3 and 69 ± 5.2 μmol/kg, respectively). This study assesses the errors for both approaches and emphasizes the importance of mesoscale and submesoscale structures on anthropogenic carbon sequestration and the distribution of carbonate parameters in the Algerian Basin. It shows that these features enhance basin ventilation and acidification. The first inventory of the anthropogenic carbon trapped by the Algerian Basin is estimated at 0.44–0.53 ± 0.06 Pg C, based on the new dataset.
... In figures, 1‰ is added to every modern fish δ 13 C value to account for the "oceanic Suess effect." This 1‰ correction factor was developed based on the Pacific, Atlantic, and Indian Oceans (Sonnerup et al., 1999), which are deeper and thus slower to equilibrate with atmospheric CO 2 changes than is the Mediterranean Sea, but is adopted in the present study because Mediterranean Sea water is primarily recharged by the Atlantic Sea via the Strait of Gibraltar, approximately every 100 years (Louanchi et al., 2009). ...
During the 8-7th centuries BCE, Greeks began establishing colonies throughout the Mediterranean region. Founded in 648 BCE, the Greek colony Himera was the meeting place for Greeks of multiple cultural backgrounds, indigenous Sicilians, and Phoenicians, and was closely connected to the broader Mediterranean world through trade. We explore evidence for diversity and cultural hybridity at Himera from the perspective of its food traditions using stable carbon and nitrogen isotope analysis of 90 humans, and fauna associated with the burials.
Results indicate diets based on C3 plants, supporting historical evidence that cereals provided most daily calories, with other plants eaten as supplemental “relishes.” Terrestrial animal protein was consumed in variable, but mostly low amounts, and there is no clear isotopic evidence for fish consumption. There are no differences in diet based on burial style, body position, burial “richness,” or age group, but some evidence for differences in diets of males and females, particularly during young adulthood. The fact that diets vary independently of several potentially prominent markers of status or ethnicity supports models of cultural hybridity in Greek colonization, wherein elements of different cultures mingled and recombined in new ways specific to the colony, rather than simple admixture or assimilation.
... The role of the MedSea as a source or sink for atmospheric CO 2 in the global carbon cycle, especially in the context of warming MedSea waters, is unclear (Nykjaer, 2009;Vargas-Y� añez et al., 2008). Several recent studies indicate a gradual change from a source to a sink over the last few decades (Louanchi et al., 2009;Taillandier et al., 2012). However, in situ measurements of the carbonate seawater system are still scarce for the MedSea. ...
The temporal evolution of the carbonate system and air-sea CO2 fluxes are investigated for the first time in the Bay of Marseille (BoM – North Western Mediterranean Sea), a coastal system affected by anthropogenic forcing from the Marseille metropolis. This study presents a two-year time-series (between 2016 and 2018) of fortnightly measurements of AT, CT, pH and derived seawater carbonate parameters at the SOLEMIO station. On this land-ocean boundary area, no linear relationship between AT and salinity in surface water is observed due to sporadic intrusions of freshwater coming from the Rhone River. On an annual scale, the BoM acts as a sink of atmospheric CO2. This result is consistent with previous studies in the Mediterranean Sea. Mean daily air-sea CO2 fluxes range between −0.8 mmolC.m−2.d−1 and -2.2 mmolC.m−2.d−1 during the study period, depending on the atmospheric CO2 sampling site used for the estimates. This study shows that the pCO2 in the surface water is predominantly driven by temperature changes, even if partially counterbalanced by biological activity. Therefore, temperature is the main contributor to the air-sea CO2 exchange variability. Mean daily Net Ecosystem Production (NEP) estimates from CT budget shows an ecosystem in which autotrophic processes are associated with a sink of CO2. Despite some negative NEP values, the observed air-sea CO2 fluxes in the BoM are negative, suggesting that thermodynamic processes are the predominant drivers for these fluxes.
... As mentioned above, long-term data series of the carbonate properties are very scarce throughout the Mediterranean Sea, and this precludes making an accurate evaluation of the degree and rate of acidification in this region. However, a modeling exercise from Louanchi et al. (2009) suggests that the Mediterranean Sea has been transformed from a source of 0.62 Gt C year À1 for atmospheric CO 2 in the 1960s to a net sink of À1.98 Gt C year À1 in the 1990s. This study also suggested that changes of surface pH in the Mediterranean Sea were not significant over this period. ...
... Data on slick coverage in other oceanic regions, including our study sites, are not available. We used annual air-sea CO 2 fluxes from Louanchi et al. (2009), and calculated fluxes for coastal (based on a coast line of 46,000 km and 3 km offshore zone) and open sea. These fluxes were multiplied with the slick coverages for the coastal and oceanic Mediterranean Sea (Romano, 1996), respectively, and corrected by a reduction factor for gas exchange over artificial slicks (Salter et al., 2011). ...
... Reduction of air-sea CO 2 flux by slicks in the Mediterranean Sea based on a total flux of À1.98 Tg C year À1 (Louanchi et al., 2009), slick coverage of 30% and 10% for coastal and open water, respectively, (Romano, 1996) and reduction of CO 2 flux in slicks by 50% (Salter et al., 2011 Romano (1996). c Based on a reduction of 50% (Salter et al., 2011). ...
... d Based on a coastline of 46,000 km and 3 km offshore zone. Louanchi et al. (2009) reported that the Mediterranean Sea is a net sink of anthropogenic CO 2 (À1.98 Tg C y -1 ). Our calculation shows that slicks can reduce CO 2 fluxes in coastal and open waters by 15% and 5% respectively (Table 2). ...
... Large geographical distribution of CO 2 data are often confined to cruises with a short sampling period (Álvarez et al., 2014;Goyet et al., 2015;Rivaro et al., 2010;Touratier et al., 2012). Numerical models have provided some insights into the carbon dynamics in the Mediterranean Sea (Cossarini et al., 2015;D'Ortenzio et al., 2008;Louanchi et al., 2009), but it remains important to constrain the system from in situ measurements to validate their output. ...
A compilation of data from several cruises between 1998 and 2013 was used to derive polynomial fits that estimate total alkalinity (AT) and total dissolved inorganic carbon (CT) from measurements of salinity and temperature in the Mediterranean Sea surface waters. The optimal equations were chosen based on the 10-fold cross-validation results and revealed that second- and third-order polynomials fit the AT and CT data respectively. The AT surface fit yielded a root mean square error (RMSE) of ± 10.6 μmol kg−1, and salinity and temperature contribute to 96 % of the variability. Furthermore, we present the first annual mean CT parameterization for the Mediterranean Sea surface waters with a RMSE of ± 14.3 μmol kg−1. Excluding the marginal seas of the Adriatic and the Aegean, these equations can be used to estimate AT and CT in case of the lack of measurements. The identified empirical equations were applied on the 0.25° climatologies of temperature and salinity, available from the World Ocean Atlas 2013. The 7-year averages (2005–2012) showed that AT and CT have similar patterns with an increasing eastward gradient. The variability is influenced by the inflow of cold Atlantic waters through the Strait of Gibraltar and by the oligotrophic and thermohaline gradient that characterize the Mediterranean Sea. The summer–winter seasonality was also mapped and showed different patterns for AT and CT. During the winter, the AT and CT concentrations were higher in the western than in the eastern basin. The opposite was observed in the summer where the eastern basin was marked by higher AT and CT concentrations than in winter. The strong evaporation that takes place in this season along with the ultra-oligotrophy of the eastern basin determines the increase of both AT and CT concentrations.
... Many studies were carried out to numerically simulate the carbonate system in the global oceans (Orr et al., 2005). In the Mediterranean Sea, box modelling estimates were made by d' Ortenzio et al. (2008), who used an array of decoupled 1-D water column biogeochemical models forced by satellite observations, and by Louanchi et al. (2009), who used a coupled data-diagnostic model approach to estimate trends in carbonate variables over the last decades. A high-resolution circulation model coupled with CO 2 module adopting a perturbation technique was used by Palmiéri et al. (2014) to estimate the anthropogenic CO 2 in the Mediterranean Sea. ...
... More than 4200 alkalinity measurements, collected through Pangea, SeaDataNet and Perseus database services, refer to several campaigns and research cruises (Table 1) in the period 1999-2011. This period is consistent with the time window of the simulation and allows one to avoid possible problems of inconsistency with older data (Louanchi et al., 2009). Given the inhomogeneity of the spatiotemporal coverage of data, average climatology profiles have been computed for a grid of 1 • × 1 • for the year and the four seasons. ...
The paper provides a basin-scale assessment of the spatiotemporal distribution of alkalinity in the Mediterranean Sea. The assessment is made by integrating the available observations into a 3-D transport–biogeochemical model. The results indicate the presence of complex spatial patterns: a marked west-to-east surface gradient of alkalinity is coupled to secondary negative gradients: (1) from marginal seas (Adriatic and Aegean Sea) to the eastern Mediterranean Sea and (2) from north to south in the western region. The west–east gradient is related to the mixing of Atlantic water entering from the Strait of Gibraltar with the high-alkaline water of the eastern sub-basins, which is correlated to the positive surface flux of evaporation minus precipitation. The north-to-south gradients are related to the terrestrial input and to the input of the Black Sea water through the Dardanelles. In the surface layers, alkalinity has a relevant seasonal cycle (up to 40 μmol kg−1) that is driven by physical processes (seasonal cycle of evaporation and vertical mixing) and, to a minor extent, by biological processes. A comparison of alkalinity vs. salinity indicates that different regions present different relationships: in regions of freshwater influence, the two quantities are negatively correlated due to riverine alkalinity input, whereas they are positively correlated in open sea areas of the Mediterranean Sea.
