A climatology and time series for dissolved nitrate in the Gulf of Maine region

Rebuck, Nathan D.; Townsend, David W.

doi:10.1016/j.dsr2.2013.09.006

Cited by 10 publications

(14 citation statements)

References 38 publications

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“…We chose these physical variables based on previous research in these waters, and in other regions, that have explored models and empirical data regarding the physical constraints on phytoplankton biomass. Finally, we compared both chlorophyll a and the physical variables to winter surface (0–39 m) nitrate concentrations [ Rebuck and Townsend , ] in Georges Bank and Gulf of Maine waters (where the majority of these measurements were taken) to understand winter nitrate limitation on the magnitude of spring phytoplankton biomass in these waters. All correlations were computed with and without time lags (monthly, seasonal, and annual).…”

Section: Methodsmentioning

confidence: 99%

“…Surface nitrate data (0 to 39 m) for Georges Bank and the Gulf Maine derived from a nutrient database compiled from many historical sources (http://grampus.umeoce.maine.edu/nutrients). Seasonal climatological means (1998 to 2012) were produced using a kriging method that resulted in a ~ 2.75 km spatial resolution [ Rebuck and Townsend , ]. Seasonal anomalies of surface nitrate (0–39 m) were calculated using the seasonal climatological means.…”

Section: Methodsmentioning

confidence: 99%

“…Seasonal anomalies of surface nitrate (0–39 m) were calculated using the seasonal climatological means. Refer to Rebuck and Townsend [] for details regarding the historical nitrate measurements and kriging methodology.…”

Section: Methodsmentioning

confidence: 99%

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Physical associations to spring phytoplankton biomass interannual variability in the U.S. Northeast Continental Shelf

et al. 2015

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The continental shelf of the Northeast United States and Nova Scotia is a productive marine ecosystem that supports a robust biomass of living marine resources. Understanding marine ecosystem sensitivity to changes in the physical environment can start with the first-order response of phytoplankton (i.e., chlorophyll a), the base of the marine food web. However, the primary physical associations to the interannual variability of chlorophyll a in these waters are unclear. Here we used ocean color satellite measurements and identified the local and remote physical associations to interannual variability of spring surface chlorophyll a from 1998 to 2013. The highest interannual variability of chlorophyll a occurred in March and April on the northern flank of Georges Bank, the western Gulf of Maine, and Nantucket Shoals. Complex interactions between winter wind speed over the Shelf, local winter water levels, and the relative proportions of Atlantic versus Labrador Sea source waters entering the Gulf of Maine from the previous summer/fall were associated with the variability of March/April chlorophyll a in Georges Bank and the Gulf of Maine. Sea surface temperature and sea surface salinity were not robust correlates to spring chlorophyll a. Surface nitrate in the winter was not a robust correlate to chlorophyll a or the physical variables in every case suggesting that nitrate limitation may not be the primary constraint on the interannual variability of the spring bloom throughout all regions. Generalized linear models suggest that we can resolve 88% of March chlorophyll a interannual variability in Georges Bank using lagged physical data.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Physical associations to spring phytoplankton biomass interannual variability in the U.S. Northeast Continental Shelf

et al. 2015

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“…Once in the Gulf, those deep nutrient-rich waters are brought to the surface by a number of physical processes, including Ekman upwelling, vertical mixing by tides and long gravity waves, and, especially, winter convective overturning, which sets the stage for the annual winter-spring phytoplankton bloom across much or all of the Gulf’s area (Thomas et al, 2003; Rebuck, 2011; Rebuck and Townsend, 2014). Vertical mixing by tides occurs throughout the year and mixes deep water nutrients into surface waters off southwest Nova Scotia, in the eastern Maine-Grand Manan Island area, around the edges of the mouth of the Bay of Fundy, and along the Northern Flank of Georges Bank.…”

Section: Introductionmentioning

confidence: 99%

Water masses and nutrient sources to the Gulf of Maine

Townsend¹,

Pettigrew²,

Thomas³

et al. 2015

j mar res

122

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The Gulf of Maine, a semi-enclosed basin on the continental shelf of the northwest Atlantic Ocean, is fed by surface and deep water flows from outside the Gulf: Scotian Shelf Water from the Nova Scotian shelf that enters the Gulf at the surface, and Slope Water that enters at depth and along the bottom through the Northeast Channel. There are two types of Slope Water, Labrador Slope Water (LSW) and Warm Slope Water (WSW); it is these deep water masses that are the major source of dissolved inorganic nutrients to the Gulf. It has been known for some time that the volume inflow of Slope Waters of either type that enters the Gulf of Maine is variable, that it co-varies with the magnitude of inflowing Scotian Shelf Water, and that periods of greater inflows of Scotian Shelf Water have become more frequent in recent years, accompanied by reduced Slope Water inflows. We present here analyses of a ten-year record of data collected by moored sensors in Jordan Basin, in the interior Gulf of Maine, and in the Northeast Channel, along with recent and historical hydrographic and nutrient data, that help reveal the nature of Scotian Shelf Water and Slope Water inflows. Proportional inflows of nutrient-rich Slope Waters and nutrient-poor Scotian Shelf Waters alternate episodically with one another on time scales of months to several years, creating a variable nutrient field upon which the biological productivities of the Gulf of Maine and Georges Bank depend. Unlike decades past, the inflows of Slope Waters of either type do not appear to be correlated with the North Atlantic Oscillation, which had been shown earlier to influence the relative proportions of the two Slope Waters, WSW and LSW, that enter the Gulf. We suggest that of greater importance in recent years are more frequent, episodic influxes of colder, fresher, less dense, and low-nutrient Scotian Shelf Water into the Gulf of Maine, and concomitant reductions in the inflow of deep, nutrient-rich Slope Waters. We also discuss evidence of modified Gulf Stream ring water that penetrated to Jordan Basin in summer of 2013.

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“…Previous budgets in the GoM (Schlitz & Cohen, ; Townsend, ) relied primarily on sparse observations. Observational capacity in the NEUS shelf continues to grow (Pettigrew et al, ; Rebuck & Townsend, ) and provide new insights (Townsend et al, , ), but the challenge of constraining time‐evolving flows over complex bathymetry along a >1000‐km boundary remains daunting. We thus complement previous work by analyzing the mean and seasonally evolving nutrient budget in a 12‐year high‐resolution physical‐biological simulation for the Northwest Atlantic.…”

Section: Introductionmentioning

confidence: 99%

A Numerical Model Analysis of the Mean and Seasonal Nitrogen Budget on the Northeast U.S. Shelf

et al. 2019

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The supply of nitrogen is a primary limiting factor for the productivity of the Northeast United States (NEUS) continental shelf. In this study, a 12‐year (1996–2007) retrospective physical‐biogeochemical simulation over the Northwest Atlantic was used to analyze the mean and seasonal NEUS shelf nitrogen budget, including the connections between shelf subregions: the Gulf of Maine/Georges Bank (GoM/GB), and the Mid‐Atlantic Bight (MAB). The model captures the primary mean and seasonal patterns of shelf circulation, nitrate, and plankton dynamics. Results confirm aspects of previous nitrogen budget analyses, including the dominance of offshore nitrogen influxes into the GoM/GB and the prominent role of riverine influxes and sedimentary denitrification in the MAB. However, detailed spatiotemporal analysis of nitrogen fluxes highlights the importance of dispersed inflows of shallow to intermediate depth waters (0–75 m), which can at times exceed the deep nitrogen influx emphasized in previous studies. A seasonal analysis shows a pronounced shift from the net import of nitrogen to the GoM/GB region during late fall and winter, to the net export of nitrogen from the region in the spring and early summer. The MAB, in contrast, consistently exports nitrogen to offshore waters. The prominence of the 0‐75m nitrogen supply has implications for the roles of Labrador Slope Water and Atlantic Temperate Slope Water on the NEUS ecosystems, as Atlantic Temperate Slope Water has greater nitrate concentrations than Labrador Slope Water at depth but often less at the surface. Results suggest the need for further study of shallow to intermediate depth inflows beyond those from the Scotian Shelf, particularly during the fall/winter of net nitrogen inflow.

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A climatology and time series for dissolved nitrate in the Gulf of Maine region

Cited by 10 publications

References 38 publications

Physical associations to spring phytoplankton biomass interannual variability in the U.S. Northeast Continental Shelf

Physical associations to spring phytoplankton biomass interannual variability in the U.S. Northeast Continental Shelf

Water masses and nutrient sources to the Gulf of Maine

A Numerical Model Analysis of the Mean and Seasonal Nitrogen Budget on the Northeast U.S. Shelf

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