Variability of the coastal current and nutrient pathways in the eastern Gulf of Maine

Brooks, David A.; Townsend, David W.

doi:10.1357/002224089785076299

Cited by 76 publications

(61 citation statements)

References 11 publications

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“…Fournier et al (1984b) show mid-summer chlorophyll concentrations of B5.0 mg m À3 at southern Scotian Shelf frontal zones separating cold, nutrient-rich surface water from more stratified conditions off the shelf. Fieldwork has shown that coupling between hydrography and nutrient transport in eastern Gulf of Maine has a significant influence on resultant biological patterns (Townsend et al, 1987;Brooks and Townsend, 1989) and these authors point out the strong temporal variability of patterns evident in individual SST satellite scenes. O'Reilly et al (1987) and O'Reilly and Zetlin (1996) present a climatological (1977-1982and 1977-1988 seasonal cycle of chlorophyll in northeast US coastal waters calculated from in situ (MARMAP) data.…”

Section: Introductionmentioning

confidence: 95%

“…The vernal circulation in the Gulf of Maine inferred from June 1983 hydrography surveys (Brooks, 1985) shows separated cyclonic flows around all three major basins. A coastal current, usually divided into the Eastern Maine Coastal Current (EMCC) and the Western Maine Coastal Current (WMCC), makes up the nearshore portion of the cyclonic flow with a branch of the EMCC often observed turning offshore into the interior of the Gulf in the vicinity of Penobscot Bay (Brooks and Townsend, 1989;Pettigrew et al, 1998). Surface thermal signatures of both the vertical mixing and residual circulation are reflected in patterns evident in satellite surface temperature data (Bisagni et al, 1996(Bisagni et al, , 2001).…”

Section: Introductionmentioning

confidence: 99%

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Satellite-measured phytoplankton variability in the Gulf of Maine

Thomas

Townsend

Weatherbee

2003

Continental Shelf Research

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107

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The first 4 years of SeaWiFS ocean color data (September 1997-August 2001 provide the first synoptic quantification of seasonal and interannual phytoplankton chlorophyll variability in the Gulf of Maine. Climatological monthly means show spatial patterns associated with the annual cycle. Concentrations are elevated throughout the year in coastal regions and over shallow banks (Georges Bank, Nantucket Shoals and Browns Bank) with a spring and fall bloom superimposed. Over deeper basins and the Scotia Shelf, a canonical North Atlantic seasonal cycle is present with low (o 1 mg m À3 ) winter (December-February) concentrations, an annual maximum in March-April (>2 mg m À3 ), reduced concentrations in summer and a fall bloom beginning as early as September in Jordan Basin but in OctoberNovember over other regions. Strong interannual variability over the 4-year time series shows the climatological seasonal features are often a biased picture of both timing and magnitude. The clearest interannual signal is of reduced chlorophyll concentrations throughout 1998, including weak spring and fall blooms. A connection between low concentrations in 1998 and local wind forcing is not evident. However, the low concentrations are coincident with negative anomalies in satellite surface temperature fields and follow the intrusion of relatively cold, low salinity slope water into the Northeast Channel which previous authors have argued is linked to changes in Labrador slope water transport induced by the North Atlantic Oscillation. Reduced concentrations in 1998 are consistent with both lower nitrate/nitrite concentrations in the intruding water as well as reduced subsurface stratification which would delay or reduce the onset of the spring bloom. r

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Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Satellite-measured phytoplankton variability in the Gulf of Maine

Thomas

Townsend

Weatherbee

2003

Continental Shelf Research

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107

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“…At this point the current branches into two segments, one that continues along the coast and another that veers offshore around the Jordan Basin Gyre. Potential mechanisms affecting the path of this offshore branch include topographic effects, offshore steering along the southwestern flank of the cyclonic gyre over Jordan Basin (Bisagni et al, 1996;Brooks and Townsend, 1989), and inshore influences of the Penobscot river plume that tend to push the current offshore (Brooks, 1994;Pettigrew et al, 1998;Xue et al, 2000). The Western segment of the MCC is fed by the inshore branch of the eastern segment together with the outflow of the Penobscot River.…”

Section: Circulation Modelmentioning

confidence: 99%

Mechanisms regulating large-scale seasonal fluctuations in Alexandrium fundyense populations in the Gulf of Maine: Results from a physical–biological model

McGillicuddy

Anderson

Lynch

et al. 2005

Deep Sea Research Part II: Topical Studies in Oceanography

148

132

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Observations of Alexandrium fundyense in the Gulf of Maine indicate several salient characteristics of the vegetative cell distributions: patterns of abundance are gulf-wide in geographic scope; their main features occur in association with the Maine Coastal Current; and the center of mass of the distribution shifts upstream from west to east during the growing season from April to August. The mechanisms underlying these aspects are investigated using coupled physical-biological simulations that represent the population dynamics of A. fundyense within the seasonal mean flow. A model that includes germination, growth, mortality, and nutrient limitation is qualitatively consistent with the observations. Germination from resting cysts appears to be a key aspect of the population dynamics that confines the cell distribution near the coastal margin, as simulations based on a uniform initial inoculum of vegetative cells across the Gulf of Maine produces blooms that are broader in geographic extent than is observed. In general, cells germinated from the major cyst beds (in the Bay of Fundy and near Penobscot and Casco Bays) are advected in the alongshore direction from east to west in the coastal current. Growth of the vegetative cells is limited primarily by temperature from April through June throughout the gulf, whereas nutrient limitation occurs in July and August in the western gulf. Thus the seasonal shift in the center of mass of cells from west to east can be explained by changing growth conditions: growth is more rapid in the western gulf early in the season due to warmer temperatures, whereas growth is more rapid in the eastern gulf later in the season due to severe nutrient limitation in the western gulf during that time period. A simple model of encystment based on nutrient limitation predicts deposition of new cysts in the vicinity of the observed cyst bed offshore of Casco and Penobscot Bays, suggesting a pathway of re-seeding the bed from cells advected downstream in the coastal current. A retentive gyre at the mouth of the Bay of Fundy tends to favor re-seeding that cyst bed from local populations.

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“…Along its "open" boundary with the North Atlantic, exchange is limited by the shoal regions of the Scotian Shelf, Browns Bank, Georges Bank, and Nantucket Shoals. At depths exceeding 100 m, the exchange is confined essentially to the channels separating Georges and Browns Banks from the Scotian Shelf; the most significant of these is the Northeast Channel (Figure 1 Townsend et al [1987] and Brooks and Townsend [1989] emphasized the importance of the coastal current system and its rich load of inorganic nutrients to the hiological productivity of the Gulf of Maine. Townsend et al [1987], using conductivity-temperature-depth (CTD) surveys and measurements of phytoplankton chlorophyll and inorganic nutrients, argued that the cold coastal band found in eastern coastal Maine is primarfly the signature of a tidal mixing plume that forms near Grand Manan Island and subsequently flows southwestward along the coast.…”

Section: Introductionmentioning

confidence: 99%

Observations of the Eastern Maine Coastal Current and its offshore extensions in 1994

Pettigrew¹,

Townsend²,

Xue³

et al. 1998

J. Geophys. Res.

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Abstract.Cold surface temperatures, reflecting Scotian Shelf origins and local tidal mixing, serve as a tracer of the Eastern Maine Coastal Current and its offshore extensions, which appear episodically as cold plumes erupting from the eastern Maine shelf. A cold water plume emanating from the Eastern Maine Coastal Current in May 1994 was investigated using advanced very high resolution radiometer (AVHRR) imagery, shipboard surveys of physical and biochemical properties, and satellite-tracked drifters. Evidence is presented that suggests that some of the plume waters were entrained within the cyclonic circulation over Jordan Basin, while the major portion participated in an anticyclonic eddy at the distal end of the plume. Calculations of the nitrate transported offshore by the plume show that this feature can episodically export significant quantities of nutrients from the Eastern Maine Coastal Current to offshore regions that are generally nutrient depleted during spring-summer. A series of AVHRR images is used to document the seasonal along-shelf progression of the coastal plume separation point. We speculate on potential causes and consequences of plume separation from the coastal current and suggest that this feature may be an important factor influencing the patterns and overall biological productivity of the eastern Gulf of Maine.

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Variability of the coastal current and nutrient pathways in the eastern Gulf of Maine

Cited by 76 publications

References 11 publications

Satellite-measured phytoplankton variability in the Gulf of Maine

Satellite-measured phytoplankton variability in the Gulf of Maine

Mechanisms regulating large-scale seasonal fluctuations in Alexandrium fundyense populations in the Gulf of Maine: Results from a physical–biological model

Observations of the Eastern Maine Coastal Current and its offshore extensions in 1994

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