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Middle Atlantic Bight salinity: Interannual variability
Abstract
Twenty-eight hydrographic surveys of the Middle Atlantic Bight (MAB) were conducted during 1977–1987 as part of the National Marine Fisheries Service's Marine Resources, Monitoring, Assessment, and Prediction program. The average temperature and salinity for Shelf Water (<34psu) in the MAB were determined for each survey. While temperature followed a well-defined seasonal cycle, the Shelf Water salinity exhibited large interannual variations. A stepwise multiple linear regression model is used to show that variations in river discharge and in precipitation can explain 70% of the year-to-year changes in the Shelf Water salinity.
... [5] In contrast to temperature, the seasonal variation in salinity on the New England shelf is small compared to either shorter time scale variations or inter-annual variations [Manning, 1991]. There is a slight freshening of the New England shelf water in spring, presumably associated with increased freshwater runoff in the Gulf of Maine and farther north [Bigelow and Sears, 1935;Manning, 1991], and possibly to local runoff from the southern coast of New England, notably the Connecticut River [Lentz et al., 2003a]. ...
... [5] In contrast to temperature, the seasonal variation in salinity on the New England shelf is small compared to either shorter time scale variations or inter-annual variations [Manning, 1991]. There is a slight freshening of the New England shelf water in spring, presumably associated with increased freshwater runoff in the Gulf of Maine and farther north [Bigelow and Sears, 1935;Manning, 1991], and possibly to local runoff from the southern coast of New England, notably the Connecticut River [Lentz et al., 2003a]. Salinity variations on the shelf are assumed to be primarily due to advection, since evaporation minus precipitation is small [Beardsley and Boicourt, 1981;Joyce, 1987]. ...
... Salinity variations on the shelf are assumed to be primarily due to advection, since evaporation minus precipitation is small [Beardsley and Boicourt, 1981;Joyce, 1987]. Potentially important contributions to salinity variability on the New England shelf include along-shelf advection of freshwater runoff and cross-shelf displacements of the shelf-slope front that separates the relatively fresh shelf water from saltier slope water [e.g., Bigelow and Sears, 1935;Manning, 1991;Linder and Gawarkiewicz, 1998;Lentz et al., 2003a]. ...
Heat and salt balances over the New England shelf are examined using 10 month time series of currents, temperature, and salinity from a four element moored array and surface heat and freshwater fluxes from a meteorological buoy. A principal result is closure of the heat budget to 10 W m-2. The seasonal variation in depth-average temperature, from 14°C in September to 5°C in March, was primarily due to the seasonal variation in surface heat flux and a heat loss in winter caused by along-shelf advection of colder water from the northeast. Conductivity sensor drifts precluded closing the salt balance on time scales of months or longer. For time scales of days to weeks, depth-average temperature and salinity variability were primarily due to advection. Advective heat and salt flux divergences were strongest and most complex in winter, when there were large cross-shelf temperature and salinity gradients at the site due to the shelf-slope front that separates cooler, fresher shelf water from warmer, saltier slope water. Onshore flow of warm, salty slope water near the bottom and offshore flow of cooler, fresher shelf water due to persistent eastward (upwelling-favorable) winds caused a temperature increase of nearly 3°C and a salinity increase of 0.8 in winter. Along-shelf barotropic tidal currents caused a temperature decrease of 1.5°C and a salinity decrease of 0.7. Wave-driven Stokes drift caused a temperature increase of 0.5°C and a salinity increase of 0.4 from mid December to January when there were large waves and large near-surface cross-shelf temperature and salinity gradients.
... Within Long Island Sound, Black Sea Bass abundance in spring and summer has increased by a staggering order of magnitude over the past decade ( However, current winter temperatures below the species' thermal limit preclude northern-stock Black Sea Bass remaining in coastal waters year-round; instead, they migrate offshore to the continental shelf once inshore fall temperatures decline past 12°C (Moser and Shepherd 2008). In this migration, they seek the warmer shelf slope waters, which are separated from colder inshore waters by a sharp thermohaline front (Fratantoni and Pickart 2007;Miller et al. 2016) located around the 34‰ isohaline (Manning 1991;Mountain 1991). Shifts in the location of this front conceivably affect the overwinter migration distance for Black Sea Bass adults and juveniles, and the effect on juveniles likely in turn impacts recruitment (Miller et al. 2016). ...
... The time spent overwintering offshore may shorten and thus accrue fewer growth benefits. In addition, the migration distance may change with location of the thermohaline front that is located at the shelf break around the 34‰ isohaline (Manning 1991;Mountain 1991). The front could move further inshore with the increasing frequency of warm core rings (Gawarkiewicz et al. 2018;Forsyth et al. 2020;Silver et al. 2023). ...
Objective
The northern stock of Black Sea Bass Centropristis striata has spatially expanded over the past decade, potentially due to warming northwest Atlantic Shelf waters affecting overwintering.
Methods
To gather empirical data on temperature‐dependent energetics, we quantified winter growth and lipid accumulation in juveniles from Long Island Sound using two experiments.
Result
Experiment 1 measured individual length growth (GR), weight‐specific growth (SGR), growth efficiency, and lipid content at constant food levels and three static temperatures (6, 12, 19°C), resulting in decreasing GR from 0.24 mm/day at 19°C (SGR = 0.89%/day) to 0.15 mm/day at 12°C (0.54%/day) to 0.04 mm/day at 6°C (0.17%/day). Even at the coldest temperature, most juveniles sustained positive GRs and SGRs; hence, the species' true thermal growth minimum may be below 6°C. Lipid accumulation was greatest at 12°C, which is close to what overwintering juveniles likely encounter offshore. Experiment 2 measured the same traits but combined a representative thermal overwinter profile (20°C → 13°C, October–March) with seasonally varying rations designed to mimic low and high levels of food availability offshore. Monthly GR and SGR responded in the direction of seasonal food level changes. The “winter pulse” consumption average of 1.7%/feeding elicited a mean GR of 0.15 mm/day and SGR of 0.55%/day, whereas the “winter dip” consumption average of 3.8%/feeding yielded faster GR (0.20 mm/day) and SGR (0.71%/day). Growth efficiency ranged between 15% and 30% and was inversely related to food consumption. In both experiments, juveniles disproportionally accumulated lipid over lean mass, with lipid proportions tripling in experiment 2 from 4% at 65 mm to 12% at 120 mm.
Conclusion
As inshore winter waters continue to warm, the energetic trade‐offs of overwinter offshore migration are likely to shift, potentially leading to a year‐round inshore Black Sea Bass presence.
... [53] Such seasonal shift in circulation pattern could affect the rate of volume transport on the shelf. Previous studies of MAB watermasses showed that the volume of the shelf water can vary seasonally with a magnitude on the order of the mean volume [Manning, 1991; Mountain, 2003]. Shelf water, defined to be water with salinity less than 34, reaches a maximum southwestward extent during the summer and retreats to a minimum volume during the winter [Mountain, 2003]. ...
... We observed that the seasons of maximum and minimum shelf water volume are characterized by mainly cross‐shelf transport, whereas seasons with the maximum change in the shelf water volume are characterized by mainly along‐shelf transport. The seasonal cycle of shelf water volume was attributed to a change in the influx of the Scotian Shelf Water [Manning, 1991]. A study by [Lentz, 2008b] using moored current meter data from the central MAB found that the magnitude of the seasonal variability of the along‐ shelf depth‐averaged flow to be comparable to the mean, on the order of 4–6 cm/s. ...
The mean and subtidal surface circulation in the central region of MAB are characterized using six years of CODAR Long Range HF Radar data. The mean surface flow is 3-7 cm/s downshelf and offshore to the southwest. Subtidal variability on the NJ Shelf is on the order of the mean offshore but several times that of the mean inshore. The response of the surface current to wind depends on the stratification and exhibits significant seasonal patterns. The flow tends to be either along-shelf or cross-shelf dominated. The seasonal climatology of the wind driven circulation for the NJ Shelf shows that the alongshore wind is correlated with cross-shelf current in the summer time, the cross-shore wind is correlated with cross-shelf current in the winter time, and the along-shore wind is correlated with along-shelf current in the transition seasons of spring and autumn. Cross-shore NW wind drives cross-shelf offshore flow in the unstratified winter season. Along-shore SW wind drives cross-shelf offshore flow in the stratified summer season. NE wind, often associated with storm events in the spring and fall, drives downshelf alongshelf flow. The Hudson Shelf Valley acts as a dynamical boundary between the northern and southern NJ Shelf with the north consistently showing weaker flow than the south. Analysis of virtual Lagrangian surface drifters show that the residence time of surface material ranges from 1 week to 8 weeks. The transport pathways are either cross- shelf or along-shelf dominated. Interannual variability in seasonal wind affects the mean winter flow; the strength of the winter cross-shore wind is correlated with the intensity of cross-shelf flow. Summer upwelling wind has little effect on the mean summer flow.
... [53] Such seasonal shift in circulation pattern could affect the rate of volume transport on the shelf. Previous studies of MAB watermasses showed that the volume of the shelf water can vary seasonally with a magnitude on the order of the mean volume [Manning, 1991;Mountain, 2003]. Shelf water, defined to be water with salinity less than 34, reaches a maximum southwestward extent during the summer and retreats to a minimum volume during the winter [Mountain, 2003]. ...
... We observed that the seasons of maximum and minimum shelf water volume are characterized by mainly cross-shelf transport, whereas seasons with the maximum change in the shelf water volume are characterized by mainly along-shelf transport. The seasonal cycle of shelf water volume was attributed to a change in the influx of the Scotian Shelf Water [Manning, 1991]. A study by [Lentz, 2008b] using moored current meter data from the central MAB found that the magnitude of the seasonal variability of the alongshelf depth-averaged flow to be comparable to the mean, on the order of 4-6 cm/s. ...
The spatial structure of the mean and seasonal surface circulation in the central region of the Mid-Atlantic Bight (New Jersey Shelf) are characterized using 6 years of CODAR long-range HF radar data (2002–2007). The mean surface flow over the New Jersey Shelf is 2–12 cm/s down shelf and offshore to the south. The detided root-mean-square (RMS) velocity variability ranges from 11 to 20 cm/s. The variability is on the order of the mean current offshore and several times that of the mean current nearshore. The Hudson Shelf Valley and the shelf break act as dynamical boundaries that define the New Jersey Shelf. The surface flow on the New Jersey Shelf depends on topography, seasonal stratification, and wind forcing. The flow is in the approximate direction of the wind during the unstratified season and more to the right of the wind during the stratified season. During the stratified summer season, the dominant along-shore upwelling favorable winds from the SW drive cross-shelf offshore flow. During the unstratified/well-mixed winter season, the dominant cross-shore NW winds drive cross-shelf offshore flows. During the transition seasons of spring and autumn, along-shore NE winds, often associated with storm events, drive energetic down-shelf, along-shelf flows. The surface transport pathways are either cross-shelf dominated during summer and winter or along-shelf dominated during the transition seasons. The residence time of surface Lagrangian drifters on the New Jersey Shelf ranged from 1 to 7 weeks with summer and autumn showing faster transport than winter and spring.
... Previous studies have documented substantial interannual variations in MAB salinities associated 544 with variations in upstream river discharge (e.g. Manning 1991, Mountain 2003. 545 ...
Analysis of forty years of tide gauge data and reanalysis wind stresses from the Middle Atlantic Bight indicate that along-shelf wind stresses are a dominant driver of coastal dynamic sea level (sea level plus atmospheric pressure) variability at daily to yearly time scales. The sea-level response to along-shelf wind stress varies substantially along the coast and is accurately reproduced by a steady, barotropic, depth-averaged model (Csanady 1978, Arrested Topographic Wave). The model indicates that the sea-level response in the MAB depends primarily on the along-shelf distribution of the along-shelf wind stress, the Coriolis frequency, the bottom drag coefficient, and the cross-shelf bottom slope. The along-shelf wind stress varies along the MAB shelf due primarily to changes in the shelf orientation. The sea-level response depends on both the local and upstream (in the sense of Kelvin wave propagation) along-shelf wind stresses. Consequently, sea-level variability at daily, monthly and yearly time scales along much of the central MAB coast is more strongly driven by upstream winds along the southern New England shelf than by local winds along the central MAB shelf. The residual coastal sea-level variability, after removing the wind-driven response and the trend, is roughly uniform along the MAB coast. The along-coast average of the residual sea level at monthly and yearly time scales is caused by variations in shelf water densities primarily associated with the large annual cycle in water temperature and interannual variations in salinity.
... It is thus unrealistic to link seasonal subpopulation variability at different locations with a single, shelfwide, environmental driver as some previous studies have suggested Licandro et al. 2001;Greene et al. 2003). Instead, the seasonal cycle could be influenced by multiple drivers operating at variable spatiotemporal scales, including spatially heterogeneous seasonality of hydrography and productivity cycles, strong cross-shelf gradients of bottom-up and top-down forcing, and a southward decline of advective inflow from upstream source populations (Manning 1991;Pershing et al. 2010). ...
Spatial population synchrony, defined as spatial covariation in population density fluctuations, exists across different temporal and spatial scales. Determining the degree of spatial synchrony is useful for inferring environmental drivers of population variability in the wake of climate change. In this study, we applied novel statistical methods to detect spatial synchrony patterns of Calanus finmarchicus on the Northeast U.S. Shelf at multiple spatiotemporal scales using unevenly distributed data. Our results reveal that C. finmarchicus subpopulations connected by advection are not necessarily in synchrony, indicating that the degree of synchrony is likely influenced by heterogeneity of local habitats. In addition, regionally synchronous environmental conditions (e.g., sea surface temperature) may not play as significant a role in influencing subregional population dynamics as was previously hypothesized. Overlooking the spatial heterogeneity of synchronous patterns at different time scales could lead to erroneous inferences of potential environmental drivers responsible for C. finmarchicus variability.
... Coastal ocean mixing with freshwater sources in the nearshore was most influential in the summer. Historically, rivers draining into the MAB exhibit peak outflow during spring, and coastal waters have the lowest salinity in summer, when the cumulative influence of seasonal runoff and precipitation are greatest (Manning, 1991;Whitney, 2010). During the summer glider deployment, multiple large precipitation events caused higher than average rainfall while the glider was in the nearshore and midshelf (17-22 July 2019; https://weather.gov/marfc/ ...
In shallow coastal shelves like the Mid‐Atlantic Bight (MAB), ocean acidification due to increased atmospheric carbon dioxide (CO2) is compounded by highly variable coastal processes including riverine freshwater inputs, nutrient loading, biogeochemical influence, coastal currents and water mass mixing, and seasonal transitions in physical parameters. Past deconstructions of carbonate system drivers in the MAB have focused on nearshore zones or single season data, and thus lack the spatial and temporal resolution required to assess impacts to important species occupying the shelf. Deconstructing highly resolved data collected during four seasonal Slocum glider deployments in the MAB, this study uses a Taylor Series decomposition to quantify the influence of temperature, salinity, biogeochemical activity, and water mass mixing on pH and aragonite saturation state from sea surface to bottom. Results show that water mass mixing and biogeochemical activity were the most significant drivers of the carbonate system in the MAB. Nearshore water was more acidic year‐round due to riverine freshwater input, but photosynthesis reduced acidity at certain depths and times. Water mass mixing increased acidity in bottom water on the shelf, particularly in summer. Gulf Stream intrusions at the shelf break during fall acted to mitigate acidification on the shelf in habitats occupied by carbonate‐bearing organisms. The relationships quantified here can be used to improve biogeochemical forecast models and determine habitat suitability for commercially important fin and shellfish species residing in the MAB.
... Freshwater enters the Mid-Atlantic Bight principally through Hudson-Raritan, Delaware, and Chesapeake Bays. Such freshwater inputs contribute to about 70% of the yearly variations in salinity in the Bight, and significantly influence hydrodynamic conditions as well (Manning, 1991). The area ranging from Chesapeake Bay in Virginia to Buzzards Bay in Massachusetts accounts for at least 124,320 km 2 (48,000 mi 2 ) of estuarine drainage. ...
... It is usually colder than 10 ∘ C and isolated from the surface by a seasonal thermocline. Cold Pool water is part of the primary shelf water mass of MAB, with salinity less than 34 practical salinity unit (psu; Manning, 1991;Mountain, 2003). The relative cold and fresh shelf water of MAB is part of a large-scale buoyancy-driven coastal current system. ...
The Mid-Atlantic Bight (MAB) Cold Pool is a distinctive cold (lower than 10 °C) and relatively fresh (lower than 34 practical salinity unit) water mass. It is located over the middle and outer shelf of the MAB, below the seasonal thermocline, and is attached to the bottom. Following this definition, we put forward a method that includes three criteria to capture and quantify Cold Pool characteristics, based on a 50-year (1958–2007) high-resolution regional ocean model hindcast. The seasonal climatology of the Cold Pool and its properties are investigated during its onset-peak-decline cycle. Three stages of the Cold Pool event are defined according to its evolution and characteristics. The Cold Pool cores travel along the 60-m isobath starting south of the New England shelf to the Hudson Shelf Valley at a speed of 2–3 cm/s. Furthermore, the northern extent of the Cold Pool retreats about 2.6 times faster than the southern extent during the summer progression. The heat balance of near-bottom waters over the MAB and Georges Bank is computed and it is found that the heat advection, rather than vertical diffusion, dominates the resulting spatial patterns of warming. Possible origins of the Cold Pool are investigated by performing a lead-lag correlation analysis. Results suggest that the Cold Pool originates not only from local remnants of winter water near the Nantucket Shoals, but has an upstream source traveling in the spring time from the southwestern flank of the Georges Bank along the 80-m isobath.
... The other region spreads from the southern New England shelf over the Delaware/Maryland shelf, and is the residual cold winter water that remains under the shallow seasonal thermocline, the so-called 'cold pool', that persists from May through October (Houghton et al., 1982;Lentz, 2008b). In contrast to the temperature, seasonal variations in both salinity (Manning, 1991;Mountain, 2003) and cross-shelf salinity gradient (Shearman and Lentz, 2003) tend to be small, except over the inner shelf (deptho60 m) where there can be an enhanced cross-shelf salinity gradient due to spring runoff (Ullman and Codiga, 2004). The plan view maps (Fig. 3b) clearly show the proximity of the 34.5 isohaline, which defines the core of the shelfbreak front at mid-depth to the bathymetry offshore of the 100 m isobath throughout the MAB. ...
A numerical simulation using the Regional Ocean Modeling System (ROMS) indicates that there was significant interannual-to-interpentadal variability of along-shelf transport and water properties over the Middle Atlantic Bight (MAB) from 2004 to 2013. To examine the relative contribution from local atmospheric forcing versus remote oceanic open boundary forcing to such low-frequency variability, we implement a suite of process oriented numerical experiments. Results show that the interannual variability is dominated by remote forcing from the open boundaries of the region rather than by local atmospheric forcing. The penetration of the Labrador Current into the region contributes to a significant increase of along-shelf transport in the winters of 2009 and 2010. By contrast, the anti-cyclonic mesoscale eddies associated with the Gulf Stream decrease the background along-shelf jet and, in certain cases, even reverse the along-shelf transport. In addition, the along-shelf transport appears to possess an interpentadal variation, i.e., weaker during 2004–2008 but stronger during 2009–2013, which is found caused by the migration of the Gulf Stream.
... Black sea bass typically congregate along the seaward edge of the SHW during the winter, following their fall offshore migration. The location of this edge proximate to the coast defines the distance necessary for black sea bass to travel to reach their winter residency and can be measured by estimating the volume of the SHW, defined by the 34 PSU isohaline [18,19]. This boundary undergoes significant seasonal and regional shifts, typically resulting in maximum volumes during the spring in southern New England and late summer in the southern MAB [14]. ...
Black sea bass (Centropristis striata) migrations are believed to play a role in overwinter survival and connectivity between juvenile and adult populations. This study investigated oceanographic drivers of winter habitat choice and regional differences between populations of juvenile and adult black sea bass. Trends in cohort strength, as a result of juvenile survival, were also identified. Oceanographic and fisheries survey data were analyzed using generalized additive models. Among the oceanographic variables investigated, salinity was the main driver in habitat selection with an optimal range of 33-35 practical salinity units (PSU) for both juveniles and adults. Preferred temperature ranges varied between juveniles and adults, but held a similar minimum preference of >8°C. Salinity and temperature ranges also differed by regions north and south of Hudson Canyon. Shelf water volume had less of an effect than temperature or salinity, but showed an overall negative relationship with survey catch. The effect of winter conditions on juvenile abundance was also observed across state and federal survey index trends. A lack of correlation observed among surveys in the fall paired with a strong correlation in the spring identifies the winter period as a factor determining year-class strength of new recruits to the population. A rank order analysis of spring indices identified three of the largest year classes occurring during years with reduced shelf water volumes, warmer winter shelf waters, and a 34 PSU isohaline aligned farther inshore. While greater catches of black sea bass in the northwest Atlantic Ocean remain south of Hudson Canyon, the species' range has expanded north in recent years.
... The MAB-SW is formed in the Gulf of Maine where the cold, low-salinity water from the Scotian Shelf joins the warmer, more saline Slope waters, which originated seaward of the shelf (Mountain, 2003). Manning (1991) defined the MAB-SW within water depths of 0-100 m as having a characteristic salinity of 32.5-33.5 staying fairly constant during the year, and a seasonally changing temperature of 4-15°C. The SAB-SW and the MAB-SW converge near Cape Hatteras, in what is known as the Hatteras Front (Savidge, 2002). ...
Climatic and oceanographic changes, as occurring at a glacial–interglacial scale, may alter the environmental conditions needed for the development of prolific cold-water coral reefs and mounds. Studies constraining the temporal distribution of cold-water corals in the NE Atlantic suggested the cyclic changes of the Atlantic Meridional Overturning Circulation as the main driver for the development and dispersal of cold-water coral ecosystems. However, conclusions were hindered by lack of data from the NW Atlantic. Aiming to overcome this lack of data, the temporal occurrence of cold-water corals in the Cape Lookout area along the southeastern US margin was explored by U-series dating. Furthermore, the local influence of the regional water masses, namely the Gulf Stream, on cold-water coral proliferation and occurrence since the Last Glacial Maximum was examined. Results suggest that the occurrence of cold-water corals in the Cape Lookout area is restricted to interglacial periods, with corals being present during the last ~7 kyr and also during the Eemian (~125 ka). The reconstructed local environmental conditions suggest an offshore displacement of the Gulf Stream and increased influence from the Mid-Atlantic Bight shelf waters during the last glacial period. During the deglacial sea level rise, the Gulf Stream moved coastward providing present-day-like conditions to the surface waters. Nevertheless, present-day conditions at the ocean sea floor were not established before 7.5 cal ka BP once the ultimate demise of the Laurentide ice-sheet caused the final sea level rise and the displacement of the Gulf Stream to its present location. Occasional presence of the Gulf Stream over the site during the Mid- to Late Holocene coincides with enhanced bottom current strength and a slightly higher bottom water temperature, which are environmental conditions that are favorable for cold-water coral growth
... The MAB-SW is formed in the Gulf of Maine where the cold, low-salinity water from the Scotian Shelf joins the warmer, more saline Slope waters, which originated seaward of the shelf (Mountain, 2003). Manning (1991) defined the MAB-SW within water depths of 0-100 m as having a characteristic salinity of 32.5-33.5 staying fairly constant during the year, and a seasonally changing temperature of 4-15qC. The SAB-SW and the MAB-SW converge near Cape Hatteras, in what is known as the Hatteras Front (Savidge, 2002). ...
Climatic and oceanographic changes, as occurring at a glacial–interglacial scale, may alter the environmental conditions needed for the development of prolific cold-water coral reefs and mounds. Studies constraining the temporal distribution of cold-water corals in the NE Atlantic suggested the cyclic changes of the Atlantic Meridional Overturning Circulation as the main driver for the development and dispersal of cold-water coral ecosystems. However, conclusions were hindered by lack of data from the NW Atlantic. Aiming to overcome this lack of data, the temporal occurrence of cold-water corals in the Cape Lookout area along the southeastern US margin was explored by U-series dating. Furthermore, the local influence of the regional water masses, namely the Gulf Stream, on cold-water coral proliferation and occurrence since the Last Glacial Maximum was examined. Results suggest that the occurrence of cold-water corals in the Cape Lookout area is restricted to interglacial periods, with corals being present during the last ~7 kyr and also during the Eemian (~125 ka). The reconstructed local environmental conditions suggest an offshore displacement of the Gulf Stream and increased influence from the Mid-Atlantic Bight shelf waters during the last glacial period. During the deglacial sea level rise, the Gulf Stream moved coastward providing present-day-like conditions to the surface waters. Nevertheless, present-day conditions at the ocean sea floor were not established before 7.5 cal ka BP once the ultimate demise of the Laurentide ice-sheet caused the final sea level rise and the displacement of the Gulf Stream to its present location. Occasional presence of the Gulf Stream over the site during the Mid- to Late Holocene coincides with enhanced bottom current strength and a slightly higher bottom water temperature, which are environmental conditions that are favorable for cold-water coral growth.
... Fresh water enters the Middle Atlantic Bight at the mouth of the Hudson-Raritan, Delaware, and Chesapeake bays. These local sources are responsible for approximately 70% of the large interannual variation in salinity in the bight (Manning, 1991). Runoff peaks in spring, when about half the annual runoff occurs (Bigelow and Sears, 1935). ...
... We now address the question of the origin of the anomalous water mass. Previous hydrographic studies in the MAB have generally defined shelf water to be water with salinity <34 [Mountain, 1991;Manning, 1991;Mountain, 2003]. Shelf water is bounded on its offshore side by the shelfbreak front, which separates lower salinity shelf water from higher salinity water over the continental slope. ...
Hydrographic surveys and moored observations in Rhode Island Sound (RIS) in water depths of 30 – 50 m, off the southern New England coast, revealed a near-bottom intrusion of anomalously warm and saline water in late fall 2009. The properties of this water mass, with peak salinity of nearly 35, are typical of slope water that is normally found offshore of the shelfbreak front, located approximately 100 km to the south. The slope water intrusion, with a horizontal spatial scale of about 45 km, appears to have been brought onto the outer shelf during the interaction of a Gulf Stream warm core ring with the shelfbreak east (upshelf) of RIS. The along-shelf transport rate of the intrusion can be explained as due to advection by the mean outer-shelf along-isobath current, although the transit time of the intrusion is also consistent with the self-advection of a dense bolus on a sloping shelf. The mechanism responsible for the large onshore movement of the intrusion from the outer shelf is not entirely clear, although a wind-driven upwelling circulation appeared to be responsible for its final movement into the RIS region. Depth-averaged salinity at all RIS mooring sites increased by 0.5 – 1 over the 3 – 4 week intrusion period suggesting that the intrusion mixed irreversibly, at least partially, with the ambient shelf water. The mixing of the salty intrusion over the shelf indicates that net cross-isobath fluxes of salt and other water properties have occurred.
... The first water mass is Chesapeake Bay plume water with a salinity of (30 psu. The second, Mid-Atlantic shelf water is defined as water with salinities between 32 and 34 and seasonally variable temperatures (Manning, 1991;Mountain, 1991). During the summer, temperature of this water mass ranges from 18 to 22°C. ...
Cross-frontal transport associated with upwelling conditions was responsible for modifying ichthyoplankton distributions across the inner continental shelf waters o⁄ the Chesapeake Bay during late August 1988. Two ichthyoplankton assemblages characteristic of the Chesapeake Bay plume and inner-continental shelf waters were defined using multivariate analysis. Mem- bers of the plume assemblage (Anchoa spp., Menticirrhus spp., and Micropogonias undulatus) were not retained within the Chesapeake Bay plume, but were instead advected 60 km onto the shelf within a low-salinity water mass. A second assemblage, dominated by several shelf- spawned taxa including Etropus microstomus, Prionotus spp. and Centropristis striata was distributed across the shelf. Atlantic croaker, M. undulatus, previously thought to be shelf- spawned exhibited a length-frequency distribution that increased from inshore to o⁄shore, and paralleled that of Anchoa spp. This cross-shelf distribution, and the abundance of small ((3.5 mm), pre-flexion larvae inshore suggests that M. undulatus spawned near the plume front and were subsequently transported o⁄shore with the plume assemblage. A mechanism for rapid cross-frontal transport is described. These findings suggest that the transport and recruitment patterns previously described for this taxon in Chesapeake Bay need to be re-examined. Larval survival and recruitment success of shelf-spawned estuarine species, like M. undulatus, are likely tied to oceanographic conditions on the inner shelf related to upwelling and downwelling conditions and plume dynamics, rather than to simple, wind-driven recruitment mechanisms. ( 1999 Elsevier Science Ltd. All rights reserved.
... Wind forcing, changes in coastline orientation, variable bathymetry, and along-shelf and cross-shelf horizontal pressure gradients caused by both sea surface slopes and horizontal density gradients contribute to that complexity. Here Mid-Atlantic Bight (MAB) and South Atlantic Bight (SAB) shelf waters meet, and a large freshwater influx enters the coastal ocean from the landward edge [Manning, 1991]. Gulf Stream meanders progress past the cape [Glenn and Ebbesmeyer, 1994a], possibly decaying and importing slope water into the coastal regime [Lee et al., 1991 ]. Gulf Stream filaments overwash the narrow shelf and participate in var- [Lillibridge et al. , 1990;Churchill and Co rnilion, 1991 ;Glenn and Ebbesmeyer, 1994a ;Churchill and Berger, 1998]. ...
Along-shelf transports across three cross-shelf lines on the continental shelf near Cape Hatteras have been calculated from moored current meter data over a continuous 24 month period in 1992-1994. The along-shelf convergence has been used to infer off-shelf export. Transport and transport convergence have been related to wind and Gulf Stream forcing and to variability in sea level at the coast. The along-shelf transport variability is primarily wind-driven and highly correlated with sea level fluctuations at the coast. Both winds and along-shelf transport exhibit a near-annual period variability. Along-shelf transport is not well correlated with Gulf Stream offshore position. Along-shelf transport convergence is highly correlated with Gulf Stream position offshore, with a more shoreward Gulf Stream position leading increased along-shelf convergence by hours to a few days. Long-period variability of 14-16 months and 1-3 months is apparent in both Gulf Stream position and transport convergence. Variability in along-shelf convergence is poorly correlated with wind, wind convergence, or coastal sea level. A likely hypothesis accounting for the observed relationship between Gulf Stream position and along-shelf transport convergence is that the Gulf Stream is directly influencing cross-shelf export processes along the outer boundary of the study site. Despite predominantly convergent flow on the shelf at Cape Hatteras, brief periods of along-shelf divergence and shoreward cross-shelf transport exist (~10% of the time just north of Cape Hatteras and ~34% of the time just south of Cape Hatteras during episodes of up to 3-8 days duration). Implied onshore flows of a few cm s-1 are tentatively identified in the moored current meter data for these periods. Satellite imagery for an extended along-shelf divergent period clearly suggests that shelf edge parcels could be advected a significant fraction of the way across the shelf.
... The historical data set consists of cross-sections taken during the SEEP I and II and the National Marine Fisheries Service Marine Resources Monitoring, Assessment and Prediction (MARMAP) programs to the MAB (Biscaye et al., 1994;Mountain, 1991;Manning, 1992). In addition, a compilation of hydrographic transects of the MAB shelf-break front that describe the variability of the physical conditions in this region, and the shelf-slope front in particular, are also used in the analysis (Lyne and Csanady, 1984). ...
Analyses of two years (1992 and 1993) of high-resolution sea surface temperature satellite images of the southern Mid Atlantic Bight (MAB), showed that unusually extensive overhang of shelf water occurs episodically, and coherently over along shelf distances of several 100km. These episodes are dubbed overrunning of the Slope Sea by shelf water. The overrunning volume has a “face” and a “back” (southern and northern limit). It transports substantial quantities of shelf water southward, and does not retreat onto the shelf, but eventually joins the western edge of the Gulf Stream in the vicinity of Chesapeake Bay. The combined analyses of satellite imagery and various in situ data further demonstrated that the shelf waters overrunning the Slope Sea were not mere surface features but reached depths between 40 and 60m. Results confirm previous concepts on shelf circulation, shelf–slope exchange and fate of shelf water. They also shed new light on shelf water budget: overrunning of the Slope Sea and southwest transport by upper slope current constitutes an important conduit for shelf water transport. Winter storms move the shelf–slope front, and with it shelf water, offshore to distances ∼10–40km. The offshore displacement of shelf water can be related to the onshore veering of the Gulf Stream near Cape Hatteras, producing a blocking effect on the shelf circulation. Such a blocking effect of the southwestward flow of shelf water in the MAB appeared to be the reason for the overrunning of shelf water off New Jersey. In addition, the excess fresh water discharge from the St. Lawerence was also observed to be related to the overflow of shelf water off New Jersey.
... While the average along-shelf current in the MAB is towards the southwest at velocities of 5 to 10 cm S-', there are periods of greater southwest speeds and periods of northeastward current reversals. This variability is greatest in the summer due to water column stratification (Epifanio et al. 1989, Flagg et al. in press) and is influenced by wind events (Bumpus 1969, Scott & Csanady 1976, Epifanio et al. 1989, local freshwater input (Bumpus 1969, Manning 1991, and input from the coastal current system (Chapman & Beardsley 1989, Mountain 1991. Greater along-shelf current speeds would effectively flush the MAB, transporting more offspring into the slope and reducing recruitment probability. ...
The current view of bluefish Pomatomus saltatrix life history holds that there are 2 distinct spawning events along the east coast of the United States which result in the recruitment of 2 juvenile cohorts to estuaries of the Middle Atlantic Bight. This two-spawning hypothesis is examined through an analysis of gonosomatic indices, larval abundances and larval distributions from both the South Atlantic and Middle Atlantic Bights. These data suggest that bluefish spawn continuously from about March to at least September, rather than in 2 distinct episodes. This continuous-spawning hypothesis raises the problem of which processes could act between spawning and estuarine recruitment to create the appearance of 2 juvenile cohorts. A model is developed which is based on large-scale circulation features of the east coast of the United States and on the hypothesis that bluefish spawn continuously as they migrate northward along the coast. The model predicts that offspring spawned in the middle of the spawning season will have a lower probability of recruitment, thereby creating a bimodal pattern of offspring survival. These results are discussed both in terms of variations in the large-scale circulation which may be responsible for creating intra- and interannual variation in recruitment, and in terms of the apparent non-adaptive nature of bluefish reproductive strategy.
... Surface temperature profiles in the GBK and MAB regions (not shown) were also persistent through the time series. Other studies have examined the variability of oceanographic processes in the region and report no substantial interannual changes in 1983 (Mountain and Holzwarth, 1989;Manning, 1991;Mountain, 1991;Manning and Strout, 2001). There also appear to have been no major perturbations in phytoplankton biomass after 1982. ...
The annual cycle of abundance for the calanoid copepod Metridia lucens and its interannual variability are described from 17 611 samples collected on 193 broad-scale plankton surveys of the US northeast continental shelf region from 1977 to 1999. The copepod's seasonal distribution is illustrated with bi-monthly geographic abundance plots. Abundance of M. lucens is compared with various environmental variables, abundance of the copepod Calanus finmarchicus, density of potential predators and the North Atlantic Oscillation (NAO) index. Metridia lucens abundance increased throughout the ecosystem during spring warming and usually reached peak levels in late spring. The highest mean densities were measured in the Gulf of Maine (GOM), where the copepod is usually found year round and exhibits a weak, decreasing west to east abundance gradient. The less dense populations located on Georges Bank and within the Middle Atlantic Bight are characterized by year-round onshore to offshore gradients that strengthen during the summer months when the copepod concentrates offshore where there is a cool layer of subthermocline water, the region often referred to as the cold pool. Interannual variability in abundance showed two persistent periods: above average values from 1979 to 1982, followed by very low levels from 1983 to at least 1987. Metridia lucens abundance in the 1990s has usually been at or above time series means. None of the environmental variables measured during the surveys could be correlated to this variability. The copepod's abundance in the GOM was not related to variation in the NAO index or to changes in predator abundance found in the region. The seasonal abundance cycle and interannual variability of M. lucens in the GOM were found to be very similar to those found for the dominant copepod, Calanus finmarchicus. Reasons for this coupling are discussed.
... [3] The salinity field is characterized by low values near the coast increasing offshore toward the shelfbreak front and with depth. In contrast to temperature, the reported seasonal variations in salinity and in cross-shelf salinity gradients are much smaller [Manning, 1991;Linder and Gawarkiewicz, 1998;Lentz et al., 2003;Mountain, 2003;Shearman and Lentz, 2003;Lentz, 2008b]. The notable exception is the inner shelf, where gradients are often enhanced due to increased river discharge during spring [e.g., Ullman and Codiga, 2004;Codiga, 2005;Chant et al., 2008aChant et al., , 2008b. ...
Four years of sustained glider observations are used to compute the seasonal cycle of hydrographic fields in the central Middle Atlantic Bight (MAB). Results reveal a large phase lag in near bottom temperatures, with peak values occurring in September at the inner shelf, in October at the mid shelf, and in November at the outer shelf. Unlike the northern MAB, the seasonal cycle explains over 70% of the near-surface salinity variability. At the inner shelf and offshore near the bottom, however, most of the variance is due to pulses in river discharge and to shifts in the position of the shelfbreak front. Cross-shelf density gradients inshore of the 60-m isobath are dominated by salinity during winter and spring, with temperature contributing significantly from August to October. This is because bottom waters near the coast are warm due to the deepening of the thermocline during fall, but offshore waters are still influenced by the cold pool. The vertical stratification seasonal variability is also large. Early in the year, stratification is small and entirely due to salinity. By May, salinity still dominates vertical gradients near the coast, but temperature and salinity contribute equally to the density stratification offshore. During summer, stratification is dominated by temperature. Temperature interannual variability was small during the sampling period, but surface salinity was anomalously low by 1.2 psu in summer 2006. The anomaly was due to larger than average discharge from the Hudson River in early summer during a period of strong upwelling favorable winds.
... Four major water masses are found on the Mid-Atlantic shelf off Virginia and the South Atlantic shelf off North Carolina. Chesapeake Bay plume (CB) water is characterized by salinity < 30 ‰ (Boicourt et al. 1987, Reiss & McConaugha 1998), Mid-Atlantic shelf water is characterized by salinities of 32 to 34 ‰ (Manning 1991 ), and Mid- Atlantic Cold-Pool Water (CPW) is characterized by temperatures <10°C (Houghton et al. 1982). CPW is found below the pycnocline on the outer shelf throughout the MAB. ...
Larval Atlantic croaker Micropogonias undulatus (1 to 7 mm in standard length) were collected on the east coast of the United States from North Carolina to Delaware during 2000. We defined 3 water-mass boundaries for potential groups of spawning Atlantic croaker using tempera- ture and salinity measured at each sampling station. We tested the hypothesis that distinct otolith chemistries existed among 3 groups of larval Atlantic croaker collected from these water masses using solution-based inductively coupled plasma-mass spectrometry. Multivariate analysis of vari- ance indicated that otolith chemistry differed significantly among water masses. Using a quadratic discriminant function, we were able to correctly classify fish from the Mid-Atlantic Bight (MAB) 73% of the time, South Atlantic Bight (SAB) 53% of the time, and Chesapeake Bay plume 36% of the time. The correct reclassification rates observed were significantly better than random. Results from this study indicate that it is possible to obtain measurable elemental concentrations from otoliths much smaller than previously analyzed (weight 0.015 to 1.976 µg). Moreover, contrary to previous studies, our results indicate that it is possible to distinguish natal signatures among larvae on different spawn- ing grounds in the MAB and SAB. Further, this new information could benefit investigations of dis- persal from offshore spawning grounds to estuaries or other nursery habitats.
... If this advective hypothesis holds true, empirical data alone may help in forecasting the arrival of these anomalous events at downstream locations. The effect of local river runoff also plays an important role in the interannual variability of salinity at many locations off the coast of Maine (Mountain and Manning, 1994;Geyer et al., 2004) and the inner Mid-Atlantic Bight (Manning, 1991). The challenge remains however in differentiating these advective influences from the heating/mixing processes that take place locally. ...
... Historically, the interannual variability in salinity in the Mid-Atlantic Bight near the Gulf of Maine has been largely associated with variability in river runoff and local precipitation (Manning, 1991) (Mountain and Manning, 1994). In the coastal ocean, upwelling and downwelling winds either trap these plumes nearshore, or disperse the low salinity water over the continental shelf, adding to the interannual variability of salinity in the Mid-Atlantic Bight (Castelao et al., 2010;Ryan et al., 1999;Yankovsky and Garvine, 1998). ...
Coastal salinity is a basic oceanographic property that is not routinely estimated by satellites. Efforts to measure ocean salinity from space are designed for large scale open ocean environments, not coastal regions. In the Mid-Atlantic coastal ocean, salinity is critical for understanding circulation patterns, river plumes, and transport, which in turn impact the status of the ecosystem. However, the spatial and temporal coverage of in situ salinity measurements in this region are sparse and do not synoptically capture salinity in the coastal ocean. We compiled ~2 million salinity records from four regional research vessels between the years 2003-2008 and found ~9 thousand salinity records that could be adequately matched to MODIS-Aqua data. We show that the spectral shape of water-leaving radiance and sea surface temperature are most correlated with in situ salinity. Four neural network models designed to predict salinity were developed for the Mid-Atlantic coastal region and three of its major estuaries (Hudson, Delaware, and Chesapeake). Our models predict salinity with RMS errors between 1.40. psu and 2.29. psu, which are much less than the null model ranges (4.87-10.08. psu) and the natural range of the system (0-32. psu). Seasonal climatologies for the Chesapeake, Delaware, and Mid-Atlantic regions based on these models are fresher than the existing NODC climatologies. We also found significant freshening trends in the Mid-Atlantic over a 6 year period.
... Previous studies of MAB watermasses on the continental shelf saw seasonal variability in the volume and the salinity of the shelf water (Manning 1991;Mountain et al. 2003). Shelfwater, defined to be water with salinity less than 34, reaches maximum southwestward extent during the summer and retreats to minimum volume during the winter (Figure 4, Mountain et al. 2003). ...
Develop and demonstrate in a Regional-scale Coastal Ocean Observatory a coupled observation and data assimilative modeling capability that contributes to our understanding of continental shelf processes, provides societal benefits, is relocatable worldwide in both collaborative and non-collaborative environments, and serves as an educational training ground for students and Navy personnel. Our approach will leverage the complementary capabilities of academic, industry and government groups through NOPP-style partnerships to develop new satellite remote sensing algorithms, new HF radar hardware and processing software, and new autonomous underwater vehicles and sensors for subsurface adaptive sampling. We will use the new technologies to sustain a continuous long-term presence in the Mid-Atlantic with enhanced coverage during an ongoing series of scientific process studies that include advanced data assimilation in coupled atmosphere/ocean physical, biological, biogeochemical, and sediment transport models. We will simultaneously develop and demonstrate the capability of a reach back cell to operate sustained autonomous ocean observing systems in remote locations world-wide. We will entrain students in the process, starting as early as their freshman undergraduate year, and we will provide training opportunities for in-service personnel from multiple agencies. OBJECTIVES Our primary objective of this data analysis project is to characterize the hydrography and stratification of the New Jersey Shelf during NLIWI/SW06 to provide a temporal and spatial context for internal wave evolution and dissipation studies. A secondary objective is to better understand the dynamical forcing responsible for the variability observed in cross-shelf transport and shelf-slope exchange during the experiment. The variability occurs on seasonal to supertidal time scales, and each can potentially affect the internal wave environment. In the end we seek connections between the shelf transport processes and the nonlinear internal waves. These science objectives can be grouped into four specific topics: 1) To characterize the hydrography and stratification of the NLIWI/SW06 sampling area, especially along the main mooring line as accurately as possible for the duration of the experiment. This result will feed into the internal wave analysis in collaboration with others.
... Estuarine landscapes of the southeastern U.S. coast are characterized by high freshwater inputs and reduced salinities in the winter. Physical parameters in the coastal ocean, such as salinity, follow this seasonality (Manning 1991). Our North Inlet transect data also demonstrated this pattern, as salinities increased system-wide from winter (Fig. 5b) to spring (Fig. 6b ). ...
Estuarine ecosystem dynamics have evolved around and respond to landscape-level influences that are dynamic in space and time. The estuarine water column is effectively the physical and biologial integrator of these landscape inputs. In this paper, we present a floating window Analysis of Covariance (ANCOVA) technique to statistically compare and contrast aquatic transect data that were taken at different times and under different tidal conditions, yet were geographically parallel and spatially articulate. The floating window ANCOVA compared two transects by testing whether the means of the dependent variable were significantly different while also testing whether the slopes of patterns in the dependent variable were significantly different. By varying the size of the floating window where the ANCOVA was run, we were able to examine how scale affected the magnitude and spatial pattern of that variable. The percentages of total models run, at a given window size, that generated significantly different magnitudes (means) and patterns (slopes) in the dependent variable were referred to as the degree of dissimilarity. Plots of window size versus degree of dissimilarity elucidated temporal and spatial variability in water column parameters at a range of scales. The advantages of this new statistical method in relation to traditional spatial statistics are discussed.We demonstrated the efficacy of the floating window ANCOVA method by comparing chlorophyll and salinity transect data taken at the North Inlet, SC estuary during flooding and ebbing tides in Winter, Spring, and Summer 1991. Chlorophyll concentrations represented the biological characteristics of the estuarine water column and salinity represented the physical processes affecting that water column. We found total dissimilarity in the magnitude of salinity data from one season to the next at all scales, but inter-seasonal similarity in spatial patterns over both short (hourly) and long (monthly) time scales. We also found a large seasonal dissimilarity in the magnitude of chlorophyll levels, as expected. Spatial patterns in phytoplankton biomass (as chlorophyll concentrations) appeared to be largely controlled by the physical processes represented with the salinity data. Often, we observed greater dissimilarity in biological and physical parameters from one tide to the next [on a given day] than from one season to the next. In these cases, the greatest flood-ebb differences were associated with landscape-level influences - from rivers and the coastal ocean - that varied greatly with direction of tidal flow. We are currently using spatially articulate aquatic transect data and the floating window ANCOVA technique to validate spatial simulation models at different scales. By using this variable-scale statistical technique to determine coherence between the actual transect data and model output from simulations run at different scales, we will test hypotheses about the scale-dependent relationships between data resolution and model predictability in landscape analysis.
... There is a relatively strong cross-shelf salinity gradient over the MAB shelf with fresher water near the coast (Fig. 9). However, the seasonal variations in both salinity (Manning 1991; Mountain 2003 ) and the crossshelf salinity gradient (Shearman and Lentz 2003) tend to be small, except over the inner shelf where there can be an enhanced cross-shelf salinity gradient due to spring runoff (March–April:Fig. 9) (Ullman and Codiga 2004; Codiga 2005). ...
Fits of an annual harmonic to depth-average along-shelf current time series longer than 200 days from 27 sites over the Middle Atlantic Bight (MAB) continental shelf have amplitudes of a few centimeters per second. These seasonal variations are forced by seasonal variations in the wind stress and the cross-shelf density gradient.
The component of wind stress that drives the along-shelf flow over most of the MAB mid- and outer shelf is oriented northeast–southwest, perpendicular to the major axis of the seasonal variation in the wind stress. Consequently, there is not a significant seasonal variation in the wind-driven along-shelf flow, except over the southern MAB shelf and the inner shelf of New England where the wind stress components forcing the along-shelf flow are north–south and east–west, respectively.
The seasonal variation in the residual along-shelf flow, after removing the wind-driven component, has an amplitude of a few centimeters per second with maximum southwestward flow in spring onshore of the 60-m isobath and autumn offshore of the 60-m isobath. The spring maximum onshore of the 60-m isobath is consistent with the maximum river discharges in spring enhancing cross-shelf salinity gradients. The autumn maximum offshore of the 60-m isobath and a steady phase increase with water depth offshore of Cape Cod are both consistent with the seasonal variation in the cross-shelf temperature gradient associated with the development and destruction of a near-bottom pool of cold water over the mid and outer shelf (“cold pool”) due to seasonal variations in surface heat flux and wind stress.
... The MAB salt balance has received less attention than the heat balance, in part because of the difficulty of making accurate moored salinity measurements (e.g., Bignami and Hopkins 2003; LSP ). In contrast to temperature, salinity does not exhibit a large seasonal variation (Bigelow and Sears 1935; Manning 1991). Mean net freshwater surface flux (precipitation minus evaporation) over the MAB is small relative to both freshwater runoff within the MAB and the along-shelf freshwater flux from the north (Beardsley and Boicourt 1981; Joyce 1987; Mountain 2003 ). ...
The mean heat and salt balances over the Middle Atlantic Bight continental shelf are investigated by testing the hypothesis that surface fluxes of heat or freshwater are balanced by along-isobath fluxes resulting from the mean, depth-averaged, along-isobath flow acting on the mean, depth-averaged, along-isobath temperature or salinity gradient. This hypothesized balance is equivalent in a Lagrangian frame to a column of water, for example, warming because of surface heating as it is advected southward along isobath by the mean flow.
Mean depth-averaged temperatures increase from north to south along isobath at a rate of 2°C (1000 km)−1 at midshelf, which is consistent with the hypothesized balance and mean surface heat flux estimates from the 50-yr NCEP Reanalysis. However, mean surface heat flux estimates from the higher-resolution 20-yr Objectively Analyzed Air–Sea Fluxes (OAFlux) reanalysis are too small to balance the along-isobath heat flux divergence implying a cross-shelf heat flux convergence. It is unclear which surface heat flux estimate, NCEP or OAFlux, is more accurate. The cross-shelf heat flux convergence resulting from the mean cross-shelf circulation is too small to balance the along-isobath heat flux divergence.
Mean depth-averaged salinities increase from north to south along isobath at a rate of 1 (psu) (1000 km)−1 at midshelf. Mean precipitation and evaporation rates nearly balance so that the net freshwater flux is too small by more than an order of magnitude to account for the observed along-isobath increase in salinity. The cross-shelf salt flux divergence resulting from the mean cross-shelf circulation has the wrong sign to balance the divergence in the along-isobath salt flux. These results imply there must be an onshore “eddy” salt flux resulting from the time-dependent current and salinity variability.
The along-isobath temperature and salinity gradients compensate for each other so that the mean, depth-averaged, along-isobath density gradient is approximately zero. This suggests that there may be a feedback between the along-isobath density gradient and the onshore salt and heat fluxes that maintains the density gradient near zero.
Understanding the variability of waters confined to the northeastern United States and Canadian continental shelf is essential in determining factors that influence hydrographic patterns and structure, changes in fisheries stocks and planktonic assemblages, and the impact of Arctic warming. Shelf waters (SHW) located between Newfoundland and Cape Hatteras are characterized by lower salinity (<34 PSU) and lower temperatures than the generally warmer and more saline slope waters located farther offshore. Significant inter-annual variability of SHW volume has been noted from previous studies within the more limited Mid Atlantic Bight sub-region. Multiple factors may impact the volume of SHW, including local and remote river runoff and precipitation, release and equator-ward transport of fresh water from the Arctic and sub-polar gyre, ice melt from Greenland, cross-shelf removal, and both vertical and horizontal mixing processes. Here, we estimate inter-annual variability of SHW volume over the large shelf domain located between Newfoundland and Cape Hatteras from 1973 through 2013. Objectively-analyzed (OA) annual mean SHW thickness and error (as a percent of data variance) is computed for each of eleven sub-regions spanning our study domain for the 41-year period. Results show significant decreasing trends in SHW volume within 5 of the 11 sub-regions (The Grand Banks through the Eastern Scotian Shelf sub-regions) in agreement with previous work which has shown a decreasing trend of northern Labrador Current transport. OA annual mean SHW volume anomalies were cross-correlated with annual mean shelf slope front (SSF) position anomalies for corresponding sub-regions, displaying a highly significant relationship for the Georges Bank, the Mid Atlantic Bight, and the DelMarVa Hatteras shelf, with higher volumes corresponding to more offshore SSF positions. Annual mean near-surface salinity anomalies, when cross-correlated with OA annual mean SHW volume anomalies, displayed significant positive correlations from the Gulf of St. Lawrence northeast to the Newfoundland shelf and displayed primarily negative correlations from the Gulf of Maine to the DelMarVa Hatteras sub-region. The North Atlantic Oscillation annual indices displayed significant cross-correlations with annual mean OA SHW volume anomalies only for the Tail of the Grand Banks and Georges Bank., There were no significant cross correlations computed between the OA annual mean SHW volume anomalies and the NAO winter index for corresponding years.
During the seasonal evolution of stratification on the New Jersey shelf in the fall, strong thermal stratification that was established in the preceding summer is broken down through wind-driven processes and surface cooling. Ten years of output from a Regional Ocean Modeling Systems run and a one-dimensional mixed layer model is used here to examine the interannual variability in the strength of the stratification and in the processes that reduce stratification in fall. Our analysis shows that the strength of the stratification at the end of the summer is not correlated with the timing of shelf destratification. This indicates that processes that occur within the fall are more important for the timing of stratification breakdown than are the initial fall conditions. Furthermore, wind-driven processes reduce a greater fraction of the stratification in each year than does the surface cooling during the fall. Winds affect the density gradients on the shelf through both changes to the temperature and salinity fields. Processes associated with the downwelling-favorable winds are more effective than those during upwelling-favorable winds in breaking down the vertical density gradients. In the first process, cross-shelf advective fluxes during storms act to decrease stratification during downwelling-favorable winds and increase stratification during upwelling-favorable winds. Second, there is also enhanced velocity shear during downwelling-favorable winds, which allows for more shear instabilities that break down stratification via mixing. Observational data and model output from Tropical Storm Ernesto compare favorably and suggest that downwelling-favorable winds act through the mechanisms identified from the Regional Ocean Modeling Systems results.
The seasonal and interannual variability in the temperature, salinity, and volume of Shelf Water (SHW) in the Middle Atlantic Bight (MAB) is described for the period 1977-1999. Large interannual variations in the volume, salinity, and, to a lesser extent, temperature of the SHW occurred that were coherent over multiple year time periods. The variations in volume and salinity originated through processes acting outside of the MAB and were advected into the region from the Gulf of Maine. On a decadal average the SHW observed in the 1990s was approximately 1°C warmer, 0.25 PSU fresher, and 1000 km3 more abundant than during the 1977 - 1987 period. The warming during the 1990s was largest in the southern part of the bight during the winter, when the SHW was more than 2°C warmer then during the earlier decade.
Interannual zooplankton abundance trends in the Middle Atlantic Bight region of the US Northeast continental shelf are described and related to variations in environmental variables for the years 1977 to 2009. Depth integrated plankton samples were collected on bimonthly broad-scale surveys of the region. Abundance information indicates that the region's zooplankton population is flourishing. Total counts and biomass levels have been mostly above average in the second-half of the sampling period. Multivariate analysis of abundance data supported these findings by classifying the time series into three consecutive groups of years defined by varying abundance levels: 1) average in the late 1970s, 2) low in the 1980s, and 3) above average from 1993 to 2009. This analysis identified eleven taxa that had similar increasing interannual abundance patterns during the time series. Evidence is presented that these changes may be related to warming temperatures in the Northwest Atlantic. The increasing abundance levels of the eleven taxa was positively correlated (p<0.01) to surface temperature measurements and the recent trends of the Atlantic Multidecadal Oscillation index. A second, smaller group of six taxa had correlated abundance trends that were variable through the years, with peak production associated with low salinity in the late 1990s.
The variability in temperature and salinity of the waters on the northeast USA continental shelf and the Gulf of Maine during the 1990s is presented and compared to that during a previous period (1978–87). A general freshening of the surface waters in the Gulf of Maine and of the shelf waters in the Middle Atlantic Bight is documented. An increase in the inflow to the Gulf of Maine of cool, low salinity surface water from the Scotian Shelf during the 1990s was responsible for the freshening. Wintertime warming of the shelf waters in the southern part of the region was noted. The deep waters of the western Gulf of Maine also exhibited a warming during the 1990s. This warming is believed due to reduced winter convective cooling, caused at least in part, by the freshening of the surface layer which increased the stratification that inhibited convection.
This project examines the role of local atmospheric forcing during the transition from relatively cold wintertime to relatively warmer springtime temperatures in the northern Middle Atlantic Bight (MAB) region during 1965–1973. A one-dimensional water column model is run for eight consecutive winter seasons with local surface heat flux used as the only external forcing. Historical data from the Nantucket Light Ship, along with modeled radiation estimates for New York and Boston are used for the heat flux calculations. Two model simulations were made for each winter season, allowing for both a qualitative and quantitative comparison of model output with observed regional temperature variability and with observed temperature changes measured at Nantucket Lightship (NLS). Interannual variability (IAV) in local atmospheric heat flux during wintertime is shown to be a dominant factor in determining springtime temperature conditions during the study period. However, the residuals from a regression analysis suggest that advective processes may have contributed to the observed temperature variability, although it is believed that the advective influence is secondary to local surface heat flux in the northern MAB for this study period.
Employing one million ship reports gathered in the years 1941–72 seasonal averages of the wind stress and its standard deviation have been computed for the shelf region of the eastern North American continent (out to a depth of 200 m). A drag coefficient is assumed which increases with wind speed, from 1.0×10⁻³ at 5 m s⁻¹ to 2.3×10⁻³ at 25 m s⁻¹. Atmospheric stratification is taken into account but its effect is shown to be small.
In the summer season the 32-year climatological wind stress is toward the northeast, having a magnitude close to 0.25 dyn cm⁻² throughout the entire shelf region. In the three other seasons the stress is directed toward the south and east being strongest in winter (1–1.5 dyn cm⁻²) and weakest in fall (0.25–0.5 dyn cm⁻²). In addition to the expected increase in magnitude with increasing latitude remarkable small-scale variability occurs. An offshore increase in stress is widespread and dominates the mid-Atlantic Bight; in winter the stress there increases from 0.5 to 1.0 dyn cm⁻² in going 200 km offshore. In the Gulf of Maine and especially in the Gulf of St. Lawrence local maxima occur; the tall of the Grand Banks 500 km from shore shows a minimum. Probably much of this variation is associated with the intensity (and frequency) of cyclonic activity rather than directly with changes in friction at the underlying surface. Some oceanographic consequences are commented on but the computations are principally intended as a data source for further research.
[1] The seasonal and interannual variability in the temperature, salinity, and volume of Shelf Water (SHW) in the Middle Atlantic Bight (MAB) is described for the period 1977–1999. Large interannual variations in the volume, salinity, and, to a lesser extent, temperature of the SHW occurred that were coherent over multiple year time periods. The variations in volume and salinity originated through processes acting outside of the MAB and were advected into the region from the Gulf of Maine. On a decadal average the SHW observed in the 1990s was approximately 1°C warmer, 0.25 PSU fresher, and 1000 km3 more abundant than during the 1977–1987 period. The warming during the 1990s was largest in the southern part of the bight during the winter, when the SHW was more than 2°C warmer then during the earlier decade.
Strong correlations were observed among subtidal longshelf currents from the Middle Atlantic Bight (MAB) to the Georges Bank region, a distance spanning 615 km. The longshelf current consisted predominantly of wind-forced motions and freely propagating events, which together accounted for 75%–90% of the longshelf current energy. Much stronger longshelf currents were observed in the MAB than on Georges Bank. The MAB/Georges Bank energy ratio for wind-forced currents on the 60 m isobath was 20. The ratio for freely propagating events was 3. The magnitudes of many of the terms in the vertically integrated wind-driven momentum equations were estimated from observations of current, pressure and surface stress, and from calculations of bottom stress. The cross-shelf momentum balance was geostrophic. Surface and bottom stress, the longshelf pressure gradient, and the Coriolis force on the cross-shelf flow were important terms in the longshelf momentum balance. An analytic model of wind-forced current, which incorporates the significant force balances, accounted for the observed longshelf variation of the wind-forced currents. Average bottom-drag and bottom-resistance coefficients estimated from current and bottom-stress records range from 4–8 (× 10⁻³) and 0.07–0.20 cm s⁻¹, respectively.
The circulation and transport of freshwater generated by an idealized buoyant source is studied using a three-dimensional primitive equation model. Freshwater enters the continental shelf, turns anticyclonically and moves downstream in the direction of Kelvin wave propagation. In the region close to the source, the flow reaches an equilibrium in the bottom boundary layer so that freshwater does not spread offshore any further. This offshore equilibrium distance increases as we move downstream until the freshwater is able to feel the presence of the shelfbreak. A shelfbreak front forms and the shelfbreak prevents any further offshore spreading of freshwater in the bottom boundary layer.Two complimentary mechanisms are responsible for the slow cross-shelf migration of freshwater and subsequent trapping of shelfbreak fronts: bottom stress and topographic changes. The shelfbreak creates an active, dynamic process preventing leakage from the continental shelf region to the slope region. However, the dynamical process that traps the front to the shelfbreak is still unclear.The location of the shelfbreak front depends on four dimensionless parameters: scaled inlet volume transport, scaled breadth, scaled “diffusivity” and scaled shelf width. We develop empirical relations for predicting the location of the frontal bottom intersection, given these parameters.
Interannual variability in the surface and bottom temperature and salinity on the U.S. northeast shelf is described by using hydrographic data from the Northeast Fisheries Science Center (NEFSC) MARMAP program. This 10 year data set provides the spatial resolution to describe spatial patterns in the variability of the shelf water properties. An empirical orthogonal function analysis is used to determine the primary modes of variability. All parameters investigated have significant first modes, which contain 40–50% of the variance in the winter and 25–35% in the summer period. All parameters, except the summer surface temperature, exhibit coherent variability across the entire shelf region from near Cape Hatteras to the central Gulf of Maine. The summer surface temperature appears to have two regions of coherent variability: in the central Middle Atlantic Bight and in the western Gulf of Maine. This regionalization is believed due to the effect of local sources of coastal runoff.
Description of the shelfbreak front in the Middle Atlantic Bight is hampered by the extreme variability of the front. In order to gain more insight into the mean frontal structure and associated baroclinic jet, historical data is used to produce two dimensional climatological fields of temperature and salinity for the region south of Nantucket shoals. Associated cross-shelf fields of density, geostrophic velocity, relative vorticity, and shallow water potential vorticity have also been computed. Historical data from a quality-controlled database (HydroBase) in the region 69-72 deg W, 39.5-41 deg N is included. Cross-shelf sections are obtained by averaging the data in nine depth bins with an average cross-shelf spacing of 10 km but an increased resolution of 4 km near the shelfbreak. The vertical averaging interval was 10 m over the shelf and upper slope waters, increasing to 50 m in the deep slope waters. The data were averaged in bimonthly periods to study seasonal trends. For inter-regional comparison, similar analyses were performed for the south flank of Georges Bank and the shelf off New Jersey. The climatological temperature and salinity are consistent with previous descriptions of the frontal hydrography. Most importantly, features such as the cold pool, the upper slope pycnostad, and the frontal boundary are well resolved when compared with synoptic sections. The temperature contrast across the front varies seasonally between 2-6 deg C near the surface and at depths of 45-65 m. The salinity contrast is 1.5-2 PSS, with little seasonal variation. The resulting cross-frontal near surface density gradients are strongest during the winter and weakest during the summer, when the seasonal thermocline is established.
The shelf-slope front (SSF) located off the northeastern United States and Canada is an oceanographic front separating colder and less-saline continental shelf waters from generally warmer and more-saline slope waters over the continental slope. The surface expression of the SSF is visible year-round using sea-surface temperature (SST) data obtained from satellite-based infrared radiometers. Availability of 20 years (1973–1992) of SSF positions, digitized from weekly satellite-derived SST charts between 75∘ and 50∘W longitude, allows a detailed spatial analysis of the seasonal variability of the SSF position between Cape Hatteras and the Tail of the Grand Banks. Results show an overall maximum seaward (shoreward) extent during winter (summer), consistent with earlier work. However, our more detailed spatial analysis shows that the eastern-most and western-most monthly SSF anomalies, relative to the long-term (1973–1992) mean, are 180∘ out of phase, with maximum seasonal SSF variability of occurring generally east of 58∘W. Furthermore, seasonal westward propagation of the seaward-most (landward-most) SSF position is evident between 50∘ and 58∘W from November to April (May–October), decreasing in amplitude towards the west. A simple Ekman coastal plume model incorporating gridded wind-stress anomalies and a constant plume depth reproduces the general seasonal cycle of the SSF along with the east-west phase shift, except in easternmost regions where SSF positional variability is maximal. The east-west phase shift results from interaction between the slowly varying (in space) wind-stress anomalies and the abrupt change in orientation of the mean along-SSF direction, from a mean of between 50.5∘ and 70.5∘W, to a mean of between 70.5∘ and 74.5∘W. A more complex Ekman coastal plume model that allows the upper layer to evolve to a uniform thickness through shear-induced mixing and a critical Richardson number criterion (hc=variable), overestimates onshore movement of the SSF south of Nantucket Shoals by a factor of 2–3 compared to August–October observations. While clearly not locally wind-forced, we speculate that a possible source of the seasonal, westward-propagating SSF meander is due to seasonal variability in the volume of shelf waters within this eastern-most region resulting from Labrador Current transport that is maximum (minimum) during fall (spring) upstream of the Tail of the Grand Banks and within the Labrador Sea. Comparisons of the seasonal movements of the satellite-derived surface SSF position with previously published sub-surface expressions of the SSF and shelf water volumes derived from hydrographic data collected within the Middle Atlantic Bight section of our domain, demonstrate decoupling of the surface wind-forced SSF from the sub-surface thermohaline-forced SSF over seasonal timescales for this westernmost region.
Surface samples have been collected in the North Atlantic in the past one hundred years for determining the ocean salinity and its temperature. A large share of the data we have used were collected by merchant vessels of weather ships of European countries and to a large extent are listed in reports, in particular in the "Bulletin Hydrographique". We investigate whether these data are relevant for determining low frequency fluctuations of the sea surface salinity. We find many crossing in the 1920s for which salinity is anomalously high compared with the climatology or with other crossings collected on the same ship line. These anomalies are indicative of a contamination of the sample. By examining hydrographic data, reports and recent experience in collectionand storage in sea water, we can attribute these large errors to unclean buckets where salt crystals dissolve into the sample and to breathing of the samples during the storage. Each of these stages contributes in estimating a too large salinity and adds to the scatter of the measurements. (D'après résumé d'auteur)
This study quantitatively characterizes annual, interannual, and decadal variability of Middle Atlantic Bight (MAB) river discharges, MAB surface salinities, Long Island Sound (LIS) surface salinities, and LIS salinity stratification via wavelet analysis. Links among rivers, salinities, and standard climate indices are investigated through correlation analysis of the complete data records and low-pass time series (including periods greater than 1.5 years). All rivers and salinities analyzed have strong annual cycles that are distinguishable from random noise. All records have interannual power, but this variability is indistinguishable from the noise background. Some MAB rivers have significant multi-decadal power (near either 18-year or 26-year periods). Correlations are strong among MAB rivers, salinities at different shelf sections, and salinities at LIS stations. Negative correlations between MAB rivers and surface salinities account for a significant part of the observed variance: up to 29% for shelf salinities and 46% for LIS salinities. Shelf and estuary salinities are positively correlated; accounting for at most 61% of the variance. LIS salinity stratification is positively correlated with river discharge (up to 36% of the variance). Interannual variability exhibits similar statistical relationships with higher correlations. Average annual cycles indicate a 1–2-month sequential lag between peak river discharge, minimum estuary salinity, and minimum shelf salinity. Weak but significant correlations indicate a tendency for high discharge, low LIS salinity, and high LIS stratification to coincide with positive intervals of the North Atlantic Oscillation Index.
Temperature data spanning the entire Middle Atlantic Bight (MAB) during 1979 are used to study the structure and evolution of the cold pool. The Nantucket Shoals and New England Shelf appear to be the souce of the coldest water found in the MAB in late winter. During the spring and summer, water within the cold pool in the New York Bight north of Hudson Canyon remains colder than any shelf water either to the northeast or southwest. Thus the coldest cold-pool water persists there as a remnant of winter-cooled water rather than being replenished by a colder upstream source, and south of Hudson Canyon, cold-pool temperatures decrease in June and July as colder water from upstream is advected southwestward along the coast. Both temperature data and direct current measurements suggest that the mean alongshore current has a minimum between Nantucket Shoals and Hudson Canyon. The alongshore variation of shelf topography appears to be responsible for the spatial variation in both the alongshelf drift speed and the thermal structure of the cold pool.
A numerical model of the wind-driven transient ocean circulation in the Middle Altantic Bight is described. The model incorporates realistic topography and covers the continental shelf between the coast and the 200 m isobath from Cape Hatteras to the southern tip of Nova Scotia. The traditional shallow-water dynanics are used, i.e, the vertically integrated and linearized equations for the flow of a homogeneous fluid driven by atmospheric pressure and wind stress fluctuations and damped by a quadratic bottom stress. The equations are integrated in time using a simple modification of Platzman's (1972) finite-difference scheme, with a 12.7 km grid spacing. At the coast, normal flow is required to vanish; at non-coastal boundaries, the equivalent surface elevation is held fixed.
Based on a limited set of available oxygen isotope measurements, it is hypothesized that the mean now in the Middle Atlantic Bight is part of a 5000 km-long buoyancy-driven, coastal current which originates along the southern coast of Greenland. This idea is consistent with most features of the known circulation of the region.
Oxygen-isotope tracer data combined with results from two linear barotropic coastal models are used to argue that the observed equatorward mean alongshelf flow in the Middle Atlantic Bight is a downstream extension of the mean alongshelf flow over the Scotian Shelf. Qualitative agreement between model results and observations supports the concept that the alongshelf pressure gradient associated with the mean alongshelf flow in the Middle Atlantic Bight has an upstream or downstream and not an offshelf origin. The role of the local large-scale general circulation is apparently to help keep the shelf water on the shelf rather than to drive the shelf mean flow.
The deep water on the continental shelf south of Montauk Point, Long Island, remains cold throughout the summer. Since this cold‐water pool is surrounded by warmer water, it appears to be formed in the winter and to persist, with only gradual modification, for several months.
The temperature and salinity of the water in this area have been observed on 20 cruises made during a 3‐year period. The cycle of temperature is described. The salinity changes in the deep water as it gradually warms are used to evaluate qualitatively whether the temperature change in each year was associated with admixture of higher‐salinity warmer offshore waters or lower‐salinity, warmer surface waters.
The average salinity of the water on the continental shelf was closely correlated with the 6‐month average river flow of the Connecticut River, and it is shown that the salinity can be predicted to within error of estimate of approximately 0.3‰ from this river flow.
The Hâ¹â¸O/Hâ¹â¶O ratio of meteoric water in eastern North America decreases with increasing latitude. The annual weighted average delta¹â¸O content of the Middle Atlantic Bight (MAB) and Gulf of Maine (GOM) rivers are -9.336%â and -10.89%â, respectively. The delta¹â¸O compositions of the major east coast rivers are 2%â enriched during summer months. By using Hâ¹â¸O and salinity measurements, both conservative properties of sea water, the geographic origin of continental shelf water can be identified. The isotope-salinity tracer method, which has been used so successfully in polar regions, is also an effective method in the temperate MAB because subpolar waters are exported to this region. The apparent dilutent of slope water is -22%â delta¹â¸O relative to standard mean ocean water. Water of this composition is presently forming in the Labrador Sea. Melt water from sea ice has nearly the same isotopic composition as the sea water from which it formed and thus may be distinguished from meteoric water. In March 1977, the New York Bight cold pool contained as much as 2.5% sea ice melt water. The Gulf of St. Lawrence is the nearest source of sea ice. The New York Bight 'cold pool' was renewed from the north between March and July, which was the extent of our sampling period.
A series of 15 hydrographic cruises in the New York Bight over 1975–1977 is described and analyzed. The cruises cover all seasons but focus primarily on spring and summer. Temperature and salinity data show wide seasonal and interannual variability. Each of the three regions—inner bight, midshelf, and outer shelf slope—has distinctive properties and dynamics.
The inner bight properties are affected primarily by river flow and wind‐driven flows up the shelf valley which often splits the freshwater surface layer into two plumes, one east and one west of the valley head. The “cold pool” temperature structure on the midshelf is different each year. The water with the lowest recorded temperature (2.58°C) was on the bottom after the thermocline formation in May 1977.
Mixing models of the inner bight confirmed previous estimates of residence time as 6.8 days and yielded K r = 5 × 10 ⁶ cm ² ·s ⁻¹ with an advective transport component of 1 cm·s ⁻¹ to the southwest. A model of the mixing of the lower layer cold pool on the midshelf with onshore, offshore, and upper layer waters yields K x = 7 × 10 ⁶ and K z = 0.1 cm ² ·s ⁻¹ as the on‐offshore horizontal and vertical diffusion coefficients.
Two seasonal volumetric temperature/salinity diagrams have been prepared for the waters of the Middle Atlantic Bight from Nantucket Shoals to Cape Hatteras, to a depth of 200 m and extending as much as 130 km beyond the edge of the continental shelf. Total volume included is 23,145.6 kms, of which about half is slope water, more saline than 35%,. Most of it is in a distinctive subsurface maximum region near 13"C, which is named the upper slope water thermostad. The less saline shelf water has #two modes di- vided by a minimum near 33.6%. The fresher mode, associated with shallow depths, is identified as coastal water; that from 33.6-35% is called shelf edge water, and much of it is found seaward of the shelf break. There is very little seasonal change in the total volume of shelf water but its geographical distribution varies, showing the effects of spring runoff and suggesting a summer influx of slope water in the northern portion of the bight. Comparison with a similar census for the Gulf of Maine and shelf waters
The volume of Atlantic Ocean water in each bivariate class with potential-temperature range of 0·5 C and salinity range of 0·1 per mille has been estimated from 105 uniformly distributed hydrographic stations. The resulting statistics are presented on a pair of characteristic diagrams, each having potential temperature and salinity as co-ordinates, potential specific-volume anomaly being represented by isopleths. Several water types stand out distinctly as separate modes. These statistics are then combined with Cochrane's for the Pacific Ocean and Pollak's for the Indian Ocean to form a pair of diagrams for the world ocean. These diagrams provide the first ocean-wide frequency distributions of water characteristics. It is found that the mean potential temperature is 3·52 C, the mean salinity is 34·72 per mille, and the mean potential specific-volume anomaly is 56 cl/ton ; these values accord with the mean temperature and salinity estimated by Krümmel in 1907.
The present paper forms a sequel to the account of the temperature of the same region (Bigelow, 1933)... the continental shelf between the offings of Cape Cod (longitude about 70°) and Chesapeake Bay;-extended southward, for occasional months, to the offing of Cape Hatteras; and with such discussion of conditions along the continental slope as is justified by occasional profiles.
Description of the 1986 oceanographic conditions on the Northeast Continental Shelf. Laboratory Reference Document 89-03, Northeast Fisheries Center
- J P W Manning Houghton R
- R Schlitz
- R C Beardsley
- B Butman
- J L Chamberlain
HOLZWARTH T. J.L and J. P. MANNING (1989) Description of the 1986 oceanographic conditions on the Northeast Continental Shelf. Laboratory Reference Document 89-03, Northeast Fisheries Center, Woods Hole, MA, 34 pp. HOUGHTON R. W., R. SCHLITZ, R. C. BEARDSLEY, B. BUTMAN and J. L. CHAMBERLAIN (1982) Mid-Atlantic Bight Cool Pool: the evolution of the temperature structure during summer, 1979. Journal of Physical Oceanogra-phy, 12, 1019-1029.
Hydrographic work on MARMAP cruises Laboratory Reference Document 80-25, Northeast Fisheries Center Jr (1891) Report upon a physical investigation of the waters off the southern coast of New England, made during the summer of 1889 by the U.S. Fish Commission schooner Grampus
- R A Karschner
KaRSCHNER R. A. (1980) Hydrographic work on MARMAP cruises. Laboratory Reference Document 80-25, Northeast Fisheries Center, Woods Hole, MA. LIBBEY W., Jr (1891) Report upon a physical investigation of the waters off the southern coast of New England, made during the summer of 1889 by the U.S. Fish Commission schooner Grampus. Bulletin of the US Fisheries Commission, pp. 391-407.
Bottom-water temperature trends in the Middle Atlantic Bight during spring and autumn, 1964–1976
- Davis
Hydrographic work on MARMAP cruises
- Kirschner
Report upon a physical investigation of the waters off the southern coast of New England, made during the summer of 1889 by the U.S. Fish Commission schooner Grampus
- Libbey
Description of the oceanographic conditions on the Northeast Continental Shelf: 1977–1985
- Manning
Description of the 1986 oceanographic conditions on the Northeast Continental Shelf
- Holzwarth
Model studies of wind driven transient circulation in the Mid-Atlantic Bight: Part I. Adiabatic boundary conditions
- Beardsley
Report on temperature, salinity, and dissolved oxygen measurements made on MARMAP surveys between October 1977–December 1978
- Patanjo
MARMAP, a fisheries ecosystem study in the Northwest Atlantic: fluctuations in ichthyoplankton-zooplankton components and their potential for impact on the system
- Sherman
Variation in Shelf Slope Front position in 1987 from Georges Bank to Cape Hatteras
- Strout