The Bay of Fundy experiences the highest tides in the world: tidal range exceeds 15 m at the head of the bay. The tides are the result of the interaction of global-scale tidal forces with the shape of the Gulf of Maine and Bay of Fundy. The time it takes the tides to circle the globe is nearly the same as the time it takes for the tide to travel to the head of the bay and back. As a result, the global-scale tide amplifies the effects of the tide within the Gulf of Maine. Each day, the tides move more than 100 km3 in and out of the bay, a volume four times greater than the discharge of the world's rivers combined. Tidal mixing causes significant suspension of sediments. Suspended sediments cause the water to be cloudy and result in reduced plant growth.2
Surface area
4,946 mi2 (12,810.1 km2)
Depth
The average depth of the bay is 75 m.3
Bathymetry including key features
The floor of the bay slopes gradually away from the coast. Tidal currents have altered the bathymetry of the sea floor through the formation of fields of sand waves and extensive mud flats. The interaction of the tides and the geology of the bay is an ongoing process that has been in effect since the development of extended tidal range at the end of the last ice age, about 8,000 years ago. This interaction has not reached equilibrium; evidence exists that the seabed of the bay is now more dynamic than ever.4
Substrate
Through both erosion and sedimentation, the tides of the Bay of Fundy have a profound impact on the sediments of the bay.5 The intertidal zone of the inner bay is dominated by broad ranges of mud flats. Subtidally, the bay's sediments are characterized by sand waves, rock outcrops and mud deposits in deeper or sheltered environments.6
Relationship to large-scale circulatory patterns of the Gulf of Maine
Circulation in the bay is a function of tidal currents and the counterclockwise flowing gyre that dominates circulation in the larger Gulf of Maine. This gyre begins as an intrusion of shelf water from the Scotian Shelf; it flows in and out of the Bay of Fundy establishing a subgyre in the bay as it exits along the coast of Maine. Cooler temperatures of the Scotian Shelf water ensure that the outer Bay of Fundy is cooler than surrounding areas.7,8,9 The counterclockwise subgyre within the bay is reinforced by the effect of the earth's rotation on tidal currents.10
Information on average (seasonal/annual) oceanographic conditions
Except for areas deeper than 100 m, the Bay of Fundy is well mixed by tidal action.11 As a result, the water column is fairly uniform in temperature and salinity and seasonal variations are minimized.12 Currents in the bay flow in a counterclockwise gyre. The inner bay, influenced by freshwater runoff from several rivers, is estuarine in character. It is warmer than the outer bay due to warming as the tides flow over exposed intertidal mudflats. 13
Presence of GoMOOS buoy
Bouy J is found, not in the Bay of Fundy proper, but in the mouth of Cobscook Bay.
Whale abundance, distribution and migratory patterns
The lower Bay of Fundy is frequented by right whales more than any other location in the Gulf of Maine.14 A portion of the mouth of Bay of Fundy is designated as a "critical habitat area" for the right whale, designated as an endangered species by the National Oceanic and Atmospheric Administration. Right whales breed in the Bay of Fundy, and other areas of the eastern Gulf, through the fall.
1 Desplanque and Mossman, 2004 2 Nova Scotia Museum of Natural History, undatedb 3 Swift et al., 1969 4 Desplanque and Mossman, 2004 5 Ibid. 6 Nova Scotia Museum of Natural History, undatedc 7 Xue, et al., 2000 8 Pettigrew, et al., 2005 9 Nova Scotia Museum of Natural History, undatedc 10 Swift et al., 1969 11 Xue, et al., 2000 12 Nova Scotia Museum of Natural History, undatedb 13 Nova Scotia Museum of Natural History, undatedc 14 Baumgartner and Mate, 2005
Bear Seamount is the westernmost extinct volcano in a chain of undersea mountains known as the Western New England Seamounts. Bear Seamount is the oldest of the chain; it was most recently active 100 millions years ago. The seamount is formed of hard substrate and is dominated by invertebrate organisms that filter their food from the surrounding water. Several species of coral grow on the Western New England Seamount.1
Much like that of a geographically isolated terrestrial island, the flora and fauna of Bear Seamount exhibit a relatively high number of species that are isolated from other populations. Several species are also found on the other side of the Atlantic, indicating that the chain of seamounts of which Bear Seamount is part form a stepping stone for species crossing the Atlantic.2
Surface area
632 mi2 (1636.87 km2)
Depth
The surface of the seamount is 1500 m below sea level.3 The steep sides of the seamount drop over 1000 m to the floor of the continental slope.4
Bathymetry including key features
The seamount has been partially buried by the deposition of fine sediments. Unlike at least one other of the New England Seamounts, there is no erosion at its base; sediments form a smooth transition from the wall of the seamount to the seafloor.5
Substrate
The upper surface of the seamount is generally covered in thick deposits of sediment, there are outcrops of volcanic rock and variously sized rocks dropped by icebergs during glaciation.6
Information on average (seasonal/annual) oceanographic conditions
The seamount lies in the path of oceanic currents flowing southwesterly along the continental slope.7
1 New England Seabirds, Undated 2 Malakoff, D., 2003 3 Census of Marine Life, 2003 4 Moore, et al., 2003 5 U.S. Geological Survey GLORIA Mapping Program 6 Ibid. 7 Moore, et al. 2003
Overview
Brown’s Bank is a shoal on the southwestern edge of the Eastern Coastal Shelf. It is closed to lobster fishing; the closure serves both as a buffer between the inshore and offshore lobster fisheries and as a source of larval supply for inshore stocks.1 The bank is also an important scallop fishing area. 2
Surface area
1,140 mi2(2952.59 km2)
Depth
∼50 – ∼100 m
Bathymetry including key features
The surface of Browns Bank is comprised of two flat plateaus.3
Substrate
Brown’s Bank is a shoal comprised of sand and gravel.4 Sand deposits of various thicknesses overlie gravel deposits which are remnants of glacial till. The sand deposits are characterized by a range of sand wave forms. A thin layer of finer grained sediments occurs on the deeper, eastern portion of the bank.5
Relationship to large-scale circulatory patterns of the Gulf of Maine
A mixture of St. Lawrence River water and the Labrador Current flows southwesterly along the Scotian Shelf. This relatively fresh, cold water flows across Brown's Bank as it flows around the western end of Nova Scotia and enters the Gulf of Maine. The topography of the bank directs some of the current in a clockwise gyre around the bank.6,7
Information on average (seasonal/annual) oceanographic conditions
Due to the shallow nature of the coastal shelf, the water column in this area is well mixed by tidal action. A clockwise gyre is a permanent feature of the bank's oceanography.8 The coastal shelf is separated from the stratified interior of the Gulf by a tidal front.9
Whale abundance, distribution and migratory patterns
Browns Bank, along with other areas in the eastern Gulf, is used by right whales as a breeding area in the fall.
Closed or protected areas
Brown’s Bank is closed by the Canadian Department of Fisheries and Oceans to lobster fishing.
1 Maine Fishermen’s Forum, 2003 2 Nova Scotia Departments of Agriculture and Fisheries and Aquaculture 3 Kostylev, et al., 2001 4 Dorsey and Pederson, 1998 5 Kostylev, et al., 2001 6 Xue, et al., 2000 7 Pettigrew, et al., 2005 8 Nova Scotia Museaum of Natural History, Undated 9 Xue, et al., 2000
The Gulf of Maine is known as one of the most productive coastal seas in the world and is famous for its groundfisheries. Most of the productivity, however, does not occur in the Central Gulf but is focused on the shallow areas that rim the Gulf, where nutrient rich waters come into contact with sunlight. With its deeper waters, the Central Gulf is relatively depauperate. Exceptions include areas of localized upwelling, such as Cashes Ledge (to the west of Wilkinson Basin) and Truxton Swell (south of Jordan Basin). 1,2
Surface area
22,796 mi2 (59,041.37 km2)
Depth
The range of depth in the Central Gulf of Maine is from ~100 to ~200 m (not including the basins).
Bathymetry including key features
The central Gulf of Maine is a broad extension of the continental shelf. Ranging in depth from 100 to 200 m, the Central Gulf is separated from dry land on its northern, western and eastern sides by the coastal shelf. To the south, it is separated from the continental shelf break and slope by Georges and Browns Banks. The Northeast Channel, between the eastern end of Georges Bank and Browns Bank, and the Great South Channel, between the western end of Georges Bank and Nantucket Shoals, connect the Central Gulf with the Northwest Atlantic. The bathymetry of the Central Gulf is dominated by three large basins, Wilkinson to the west and Georges and Jordan to the east.
Substrate
Much of the Central Gulf of Maine, particularly its basins, is covered in thick deposits of mud. Unsorted glacial till is found in glacial moraines such as Truxton Swell to the south of Jordan Basin and Sewell Ridge to the north of Georges Basin. Much of the eastern portion of the Central Gulf is covered with modified glacial till - sand mixed with silt, clay and gravel. Gravel, with occasional boulders predominates on Platts Bank and Fippennies Ledge, high points in the northwestern portion of the Central Gulf. Cashes Ledge, and other high points in the same area, are formed by bed rock.3,4
Relationship to large-scale circulatory patterns of the Gulf of Maine
The circulation of the Gulf of Maine is comprised of a counterclockwise gyre that traces the coast from Nova Scotia to Cape Cod. This pattern is driven in large part by temperature; in spring, water in the interior of the Gulf begins to warm while water on the edge of the continental shelf and the slope outside the Gulf are cooling. As the water in the interior Gulf warms, it expands, becoming less dense and lighter. The difference in density between these more buoyant waters and cooler offshore waters creates a pressure gradient. The force of this gradient establishes a “downhill” flow of water away from the coast and the action of Coriolis forces (resulting from rotation of the earth) turns it toward the west. The resulting westerly flowing coastal current helps to draw water into the Gulf of Maine.
Relatively fresh, cold water enters the Gulf of Maine over the Scotian Shelf. It flows northeastward around the tip of Nova Scotia. After a turn through the Bay of Fundy, this current flows southwestward, setting up the coastal current that dominates circulation in the Gulf of Maine. Riverine discharge and tidal flows contribute to the coastal current. Dense, warmer and more saline water from the continental slope outside of the Gulf enters the Gulf through the Northeast Channel, a deep valley between Georges Bank and Browns Bank. It flows into Georges Basin and contributes to counterclockwise gyres that flow over both Georges and Jordan Basins. Outflow from the Gulf occurs through the Great South Channel and upper layers of the Northeast Channel.
The dynamics of the coastal current that flows southwestward along the coast of Maine divides the central Gulf of Maine into two oceanographically distinct areas. The eastern portion of this current is relatively fast moving and somewhat colder than the western portion of the current. Where the two meet, at the mouth of Penobscot Bay, the faster moving eastern current is, to a large degree, deflected offshore. These waters are, in turn, entrained in the counterclockwise gyres that flow over Georges and Jordan Basins. This process divides the interior Gulf into eastern and western portions that are relatively isolated from one another.
Smaller versions of the Gulf scale counterclockwise gyre follow the contours of the three major basins of the Gulf, Wilkinson in the eastern Gulf and Georges and Jordan Basins to the west. Clockwise gyres circulate over Georges and Browns Banks, the large underwater deposits that separate the Gulf of Maine from the Northwest Atlantic.5,6
Information on average (seasonal/annual) oceanographic conditions
The circulation of the Gulf has a distinct seasonal pattern. The counterclockwise gyre takes shape in the early spring. As the season proceeds, the discharge of freshwater from over sixty rivers in the Gulf watershed contributes to the currents. The action of the tides strengthens the summer circulation. In addition, the warming of the surface of the ocean results in stratification; a warmer layer floats on top of a mid-depth layer that preserves winter temperatures and salinities. It, in turn, is underlain by more saline “bottom water”. Stratification is most pronounced in the deeper areas of the western Gulf. The counterclockwise gyre is established in the top layer; the current picks up speed as the top layer slides over the middle layer. These currents reach their broadest extent and greatest speeds by the end of December. Then, cooling of the atmosphere results in cooling of the ocean surface. As it cools, it sinks, replacing the stratified layers with well mixed waters. As the currents mix downward, they are slowed by the friction they encounter when they reach the bottom. By February, the counterclockwise circulation pattern is no longer evident.7
There is considerable variation in the circulation patterns of the Gulf of Maine from year to year. Variations in the temperature and volume of water flowing into the Gulf, in the range of atmospheric temperatures affecting the Gulf, and in the size and timing of the spring freshet affect the scale and duration of the various gyres that define Gulf circulation patterns.
Presence of GoMOOS buoy
Buoy N is located in the Northeast Channel.
1 Thomas et al., 2003. 2 Conkling, 1995 3 Dorsey and Pederson, 1988 4 NEFMC, 2004 5 Xue, et al., 2000 6 Pettigrew, et al., in press 7 Xue, et al., 2000
The continental slope marks the transition between the continental shelf and the deeper waters of the North Atlantic. The edge, or shelf break, generally occurs at ~200 m. in most places. At this depth the bottom falls away relatively steeply until it meets the continental rise, which slopes gradually to the deepest areas of the North Atlantic.1
Surface area
9,392 mi2 (24,325.17 km2)
Depth
~100 to ~2000 m (the shallowest depth occurs in a few places where the most rapid change in slope occurs at 100 m)
Bathymetry including key features
The upper slope has a gradient of 7-8 degrees; it flattens with depth as it meets the continental rise.2 More than fifteen canyons mark the continental slope where it passes along the southern edge of Georges Bank.3 The larger canyons are as deep as 400 m and as wide as 5 km.4 These canyons provide habitat for a variety of species not found on the smoother portions of the continental slope.5
Substrate
In general, the substrate of the continental slope is comprised of sandy and clayey silt.6 Shallower portions of the slope are sandy. Below a line found at 250 m – 300 m sediments are characterized by silt and clay. The canyons are characterized by coarse sediments and rock outcrops. Occasional boulders occur that were deposited by glaciers and pockets of sand are found that are formed as a result of slumping of slope sediments.7
Relationship to large-scale circulatory patterns of the Gulf of Maine
Currents in the vicinity of the continental slope are isolated from the Gulf of Maine by Georges Bank, the eastern coastal shelf and the Scotian shelf. Dense, warmer and more saline water from the continental slope outside of the Gulf enters the Gulf through the Northeast Channel. Surface waters from the Gulf exit the Gulf through the Great South Channel and the Northeast Channel. The clockwise gyre that occurs on Georges Bank creates a front between the waters of the Bank and the shallower waters of the continental slope.
Information on average (seasonal/annual) oceanographic conditions
The oceanography of the continental slope is characterized by three vertical layers. A deep cold layer comprises two thirds of the water column. A middle warmer layer comprises the majority of the remainder of the water column. Seasonal warming creates a still warmer third layer during the summer months. This layer penetrates no more than 200 m of slope waters. Eddies of the Gulf Stream are the principle source of variability in slope waters. Eddies take the form of either warm or cold core rings, which persist for several months. Ranging in size from 150 m to 230 m in diameter at the surface, such rings extend, in the shape of a funnel, as much as 2000 m in depth. The exchange of water by means of Gulf Stream rings has a significant impact on the oceanography of the continental slope and shelf.8
1 New England Seabirds, Undated 2 U.S. Geological Survey GLORIA Mapping Program, Undated 3 Dorsey and Pederson, 1998 4 U.S. Geological Survey GLORIA Mapping Program, Undated 5 Dorsey and Pederson, 1998 6 Ibid. 7 New England Fisheries Management Council, 2003 8 Ibid.
Overview
The Eastern Coastal Shelf forms a broad, shallow area of the Gulf of Maine that extends from the southwestern tip of Nova Scotia. It supports fisheries for scallops, lobsters and groundfish.1
Surface area
3,067 mi2
Depth
Intertidal zone to ~100m.
Bathymetry including key features
Brown's Bank is a dominant feature of the seaward edge of the Eastern Coastal Shelf. A bedrock channel over 100m in depth separates the bank from the rest of the Eastern Coastal Shelf.2
Substrate
In shallow areas, where tidal energy has winnowed away finer sediments, the bottom is characterized by sand and gravel deposits. Deeper waters include scattered fields of sand waves and some areas where silt and clay have accumulated.3
Relationship to large-scale circulatory patterns of the Gulf of Maine
Cool and relatively fresh currents flow from the Scotian Shelf across the Eastern Coastal Shelf before contributing their flows to the Eastern Maine Coastal Current.4,5
Information on average (seasonal/annual) oceanographic conditions
Due to the shallow nature of the coastal shelf, the water column in this area is well mixed by tidal action. The coastal shelf is separated from the stratified interior of the Gulf by a tidal front.6
Presence of GoMOOS buoy
Buoy L is located west of Yarmouth, Nova Scotia.
1 Nova Scotia Departments of Agriculture and Fiaheries and Aquaculture, Undated 2 Kostylev, et al., 2001 3 Nova Scotia Museum of Natural History, Undatedf. 4 Xue, et al., 2000 5 Pettigrew, et al., 2005 6 Xue, et al., 2000
This physiographic region combines two geographic features that we describe separately below.
Georges Bank
Overview
Georges Bank is an underwater shoal, left behind by retreating glaciers several thousand years ago. The bank, as shallow as 30 m on its northwestern edge, creates a barrier between the Gulf of Maine and the northwest Atlantic Ocean. Exchange is limited to that which occurs over the Scotian shelf, to the east; through the Northeast Channel between the eastern end of the bank and the Scotian Shelf; and through the Great South Channel, between the western end of Georges and Nantucket Shoals. The topography and position of the bank result in upwelling of nutrient rich waters circulating in the Gulf of Maine. These nutrients, introduced into the sunlit waters over the bank, support very high rates of productivity, including many species of commercial importance. The fish stocks of the bank supported economies on both sides of the Atlantic for three or four centuries. The innovation of the otter trawl and the advent of a very mobile international fishing fleet combined to decimate the fish stocks of Georges Bank in the late 20th century. With stringent fisheries controls in place, some stocks are showing signs of recovery. Others, including the historically important cod, are not.1,2
Surface area
16,191 mi2
Depth
3 (Georges Shoal) to ~200 m
Bathymetry including key features
The formation of Georges Bank resulted from the deposition of mixed sediments by retreating glaciers. The subsequent rise in sea level and the action of currents, storms and tides have shaped the deposited material into an oval shaped shoal. The northern edge forms a steep slope; the southern edge is broad and gently sloping.
Where Georges Bank is shallower than 50 m, particularly on the central part of the Bank as well as the northeast peak, ridges of sand 10 to 40 m high and up to 90 km long are found. These ridges trend northwest and southeast and are parallel to the direction of the tidal currents. Smaller dunes are found on top of the ridges running perpendicular to the ridges themselves. The deeper portions of the Bank, to the east, are relatively smooth. The break between the ridges of the shallower bank and the smoother areas of the deeper bank occurs at 50 m and is abrupt; it is also the location of the tidally mixed front that forms in the summer.3 3 The edge of the bank, where it drops away to the central Gulf of Maine to the north and the continental slope to the south, occurs at 100 m. On its southeastern margin, the bank is incised by submarine canyons.
Storms and tides continually rework the surface sediments of the bank.4,5
Substrate
The Georges Bank substrate is predominantly sand. On the shallower portions of the bank, the sand is coarse and has been worked into ridges and dunes by tidal currents and storms. Finer sand is found on the deeper portions of Georges Bank. Gravel is found on the northern edge of the Bank. Georges Bank is no longer receiving sediments; as a result, it is slowly being eroded, and, as finer grained sediments are removed, its surface is becoming coarser.
Relationship to large-scale circulatory patterns of the Gulf of Maine
The counterclockwise gyre that dominates surface circulation in the Gulf of Maine flows southerly along the western coast of the Gulf. A portion of this flow branches off and flows eastward onto the northwest flank of Georges Bank (the remainder exits the Gulf through the Great South Channel).
There is a high degree of fluctuation in the oceanography of George’s Bank from year to year. This is related to larger-scale forces that affect the oceanography of the entire Gulf of Maine; they include large-scale shifts in atmospheric pressure (known as the North Atlantic Oscillation), variations in the formation of Labrador Sea water, and sea ice coverage.6
Information on average (seasonal/annual) oceanographic conditions
Tidal energy from the larger Gulf of Maine contributes to the clockwise gyre over Georges Bank. The water flowing over the Bank is distinct from that in the Gulf proper creating a frontal zone at about 60 m. The strong tidal currents occurring on the Bank keep its waters well-mixed and cool, contributing to the front between the Bank and the adjacent, seasonally stratified and warmer waters of the Gulf. Surface winds and waves contribute to mixing and affect the location of the tidal front.7
As warming of the surface layer occurs in the summer, the gyre over the Bank tends to become a closed loop; however, storms and intrusion of warm-core rings from the Gulf Stream, flowing offshore of the bank’s southern edge, can disturb the gyre and allow for exchange of water with neighboring water masses. Currents flowing southwesterly along the southern flank of the Bank either recirculate on the Bank or continue westward into the Mid-Atlantic Bight.8
1 NEFSC, 2000 2 NEFSC, 2003 3 U.S. GLOBEC: Long-Term Moored and Lagrangian Measurements as Part of a Georges Bank Study, undated. 4 Backus, et al., 1987 5 NEFMC, 2003 6 U.S. Implementation Team, 1997 7 Xue, et al., 2000 8 U.S. GLOBEC Implementation Team, 1997.
Great South Channel
Overview
The Great South Channel is a prominent feature in the bathymetry of the Gulf of Maine; along with the Northeast Channel, it provides an oceanographic connection between the Gulf of Maine and the Northwest Atlantic Ocean. The channel is a transit route for the endangered Northern Right Whale as it migrates between summer and winter habitats.
Surface area (percentage of total)
2,007 mi2 2%
Depth
~50 to ~100 m
Bathymetry including key features
The funnel-shaped Channel is wider and deeper at its northern end.1
Substrate
Sediments include gravel pavement and mounds, occasional boulders, sand with ripples generated by storms, and scattered mussel beds.
Relationship to large-scale circulatory patterns of the Gulf of Maine
In general, water flows into the Gulf from the Scotian Shelf and through the Northeast Channel at depth (river discharge during the spring freshet makes up a third source). Outflow occurs through the Great South Channel and mid and surface layers of the Northeast Channel.2,3,4
Information on average (seasonal/annual) oceanographic conditions
The Great South Channel is well mixed due to tidal currents and the existence of a frontal system between Gulf of Maine waters and those of the Continental Slope.5 The front separates the warmer, surface, stratified waters of the Gulf to the north from the cooler, tidally mixed waters south of the front.6
Whale abundance, distribution and migratory patterns
A portion of the Great South Channel is designated as a “critical habitat area” for the Northern Right Whale, designated as an endangered species by the National Oceanic and Atmospheric Administration. Right whales feed on plankton in the Great South Channel in mid to late spring.
1 NOAA, Undated 2 Xue, et al., 2000 3 Pettigrew, et al., 2005 4 Maine Ecosystem Dynamics Modeling Laboratory, Undated 5 Velntine, 1999 6 NOAA, Undated
Overview
Georges Basin is the deepest of the three large basins in the Gulf of Maine.
Surface area
1,587 mi2
Depth
~370 m (deepest point in the Gulf of Maine)
Bathymetry including key features
Thick deposits of mud obscure the bathymetry of the underlying bedrock features in Georges Basin.1 The surface of the bottom is featureless except for small mounds.2
Substrate
Georges Basin is covered in thick deposits of mud.3,4 The sediment-water interface within Georges Basin is characterized by a layer of turbid water that is tens of meters deep. The turbidity of due to the suspension of fine particles.5
Relationship to large-scale circulatory patterns of the Gulf of Maine
Water from the continental slope enters the Gulf of Maine at depth through the Northeast Channel and accumulates in Georges Basin.6 A portion of the Gulf's coastal current that turns offshore at Penobscot Bay. Some of this current is entrained in turn by a gyre that flows in a counterclockwise direction over Georges basin.7,8
Information on average (seasonal/annual) oceanographic conditions
The oceanography of Georges Basin is characterized by a counter clockwise gyre. These currents are strongest in the spring and summer. It is estimated that the deep waters of the Gulf of Maine, such as in Georges Basin, are replaced every 10-12 months.9
1 New England Fisheries Management Council, 2004 2 Valentine, 2002 3 New England Fisheries Management Council, 2004 4 Dorsey and Pederson, 1998 5 Pilskaln, et al., 1998 6 Nova Scotia Museum of Natural History. Undated 7 Xue et a., 2000 8 Pettigrew, et al., 2005 9 Xue, et al., 2000
Overview
Jordan Basin is one of three large basins in the Gulf of Maine.
Surface area
2,585 mi2
Depth
~310 m
Bathymetry including key features
Thick deposits of mud obscure the bathymetry of the underlying bedrock features in Jordan Basin.1 The surface of the bottom is featureless except for small mounds.2
Substrate
Jordan Basin is covered in thick deposits of mud.3,4 4 The sediment-water interface within Jordan Basin is characterized by a layer of turbid water that is tens of meters deep. The turbidity is due to the suspension of fine particles.5
Relationship to large-scale circulatory patterns of the Gulf of Maine
Water from the continental slope enters the Gulf of Maine at depth through the Northeast Channel. It accumulates first in Georges Basin and then crosses a sill into Jordan Basin.6 A portion of the Gulf's coastal current turns offshore at Penobscot Bay. Some of this current is entrained in turn by a gyre that flows in a counterclockwise direction over Jordan basin.7,8
Information on average (seasonal/annual) oceanographic conditions
The oceanography of Jordan Basin is characterized by a counter clockwise gyre. These currents are strongest in the spring and summer. It is estimated that the deep waters of the Gulf of Maine, such as in Jordan Basin, are replaced every 10-12 months.9
Presence of GoMOOS buoy
Buoy M, is located in Jordan Basin.
1 New England Fisheries Management Council, 2004 2 Valentine, 2002 3 New England Fisheries Management Council, 2004 4 Dorsey and Pederson, 1998 5 Pilskaln, et al., 1998 6 Nova Scotia Museum of Natural History. Undated 7 Xue et a., 2000 8 Pettigrew, et al., 2005 9 Xue, et al., 2000
Overview
Ranging from Cape Ann in the western Gulf of Maine to the Bay of Fundy in the east, the Northern Coastal Shelf encompasses a heterogeneous variety of habitat types and bathymetry. The coast is incised with a great variety of embayments and estuaries; intertidal areas are characterized by sand beaches, mudflats, saltmarshes and rocky shores. Like other shallow areas of the Gulf, where tidal action provides a steady supply of nutrients to well lit surface waters, the Northern Coastal Shelf is highly productive. Once supporting fisheries for groundfish, lobster, herring, and other species, the Northern Coastal Shelf is now dominated by lobster fishing. Coastal development has resulted in habitat destruction and pollution.1
Surface area
5,699 mi2
Depth
Intertidal zone to ~100 m
Bathymetry including key features
The bathymetry of the nearshore reflects in many cases the topography of the adjacent shoreline: bedrock peninsulas extend underwater as bedrock features, sandy beaches are matched underwater by gently sloping areas, waters offshore of cliffs reach steep depths quickly, and marshes and mud flats are mirrored by subtidal deposits of fine sediments.2
Jeffrey's Ledge is a glacial deposit that forms a curving shoal 33 miles long at the western terminus of the Northern Coastal Shelf. From 40-70 m deep, the topography of Jeffrey's Ledge creates an upwelling zone that attracts a wide variety of marine life.3,4
Substrate
Substrate in this area of the Gulf of Maine is extremely heterogeneous; it includes bedrock, sand, gravel, silt and mud, and an almost infinite range of combinations, occurring at a variety of scales. Sixty meters marks the point of lowest sea level since the last ice age. The passage of sea level through this depth range removed many of the unconsolidated sediments; as a result, bedrock predominates in much of the shallow waters of the Northern Coastal Shelf.5
Relationship to large-scale circulatory patterns of the Gulf of Maine
The oceanography of the Northern Coastal Shelf is dominated by coastal currents that flow southwesterly along the coast. These currents are a component of the counterclockwise gyre that dominates gulf-scale circulation.6,7
Information on average (seasonal/annual) oceanographic conditions
The spring freshet strengthens the coastal current in April through June and results in a decrease in salinity. The eastern portion of this current is relatively fast moving and somewhat colder than the western portion of the current. Where the two meet, at the mouth of Penobscot Bay, the faster moving eastern current is, to a large degree, deflected offshore. The portion of the current that is not deflected flows through to the west. The amount of flow through varies from year to year. The western coastal current reverses for a brief period every spring, sometimes weakly and directed offshore, sometimes strongly and in a northeasterly direction.8,9
Due to the shallow nature of the coastal shelf, the water column in this area is well mixed by tidal action. The coastal shelf is separated from the stratified interior of the Gulf by a tidal front.10
Presence of GoMOOS buoy
Five GoMOOS buoys are deployed along the Northern Coastal Shelf. They include buoys B, C, E, F, and I.
1 Woodward, 2004 2 Dorsey and Pederson, 1998 3 Whale Center of New England, Undated 4 Blue Ocean Society for Marine Conservation, Undated 5 Dorsey and Pederson, 1998 6 Pettigrew, et al., In Press 7 Xue, et al. 2000 8 Pettigrew, et al., In Press 9 Xue, et al., 2000 10 Xue, et al., 2000
In an earlier version of this map we did not distinguish between these two areas which we now divide at the 100 m isobath. The following description applies to both areas combined.
Overview
The Scotian Shelf is a very broad coastal shelf that extends from the coast of Nova Scotia to the edge of the continental slope. Approximately 60 miles wide at its southern extreme, near the Northeast Channel, the shelf broadens as it trends towards the northeast. Currents are characterized by a year-round, near-shore flow from the northeast to the southwest; it is known as the Nova Scotia Current. Influenced by the Gulf Stream to the south and the Labrador Current to the north, the waters of the Scotian Shelf support a wide variety of organisms. Tidal currents, seasonal cooling and upwelling related to bathymetric features return nutrients to sun-lit surface waters and contribute to the high productivity of shelf waters. The Scotian Shelf supports commercial fisheries for groundfish, lobsters and other species.3
Surface area
14,084 mi2
Depth
Intertidal to ~200 m
Bathymetry including key features
The bathymetry of the Scotian Shelf is marked by a broad trough, punctuated by a series of small, isolated banks, that runs the length of the shelf between the shallower coastal area and a series of large banks that mark the outer edge of the shelf. The most prominent of these large banks is Brown's Bank which forms the western terminus of the Scotian Shelf. 4,5
Substrate
The substrate of the Scotian Shelf varies according to its bathymetry: the banks are comprised of coarser sediments, such as sand and gravel, while the basins are characterized by finer-grained sediments such as clay. Boulders that dropped from the bottoms of melting glaciers occur occasionally. 6
Relationship to large-scale circulatory patterns of the Gulf of Maine
Currents flowing southwestwardly along the Scotian Shelf flow around the tip of Nova Scotia and contribute to the establishment of the counterclockwise gyre that characterizes currents in the Gulf of Maine. 7,8
Information on average (seasonal/annual) oceanographic conditions
On average, currents flow southwestardly along the Scotian Shelf. Derived from a mixture of St. Lawrence River outflow and Labrador currents, Scotian Shelf currents are are relatively fresh and cool. In the summer, shelf waters are stratified. Mixing occurs in the winter as surface waters cool and sink. Smaller scale oceanographic features, such as estuarine circulation, coastal upwelling, tidal fronts and shelf-break fronts, contribute to mixing of the shelf waters. 9
1 Cok, et al., 1965 2 Nova Scotia Museam of Natural History, Undated. 3 Nova Scotia Departments of Agriculture and Fisheries and Aquaculture, Undated 4 Nova Scotia Museam of Natural History, Undated. 5 Kostylev, et al., 2001 6 Nova Scotia Museam of Natural History, Undated. 7 Pettigrew, et al., 2005. 8 Xue, et al., 2000. 9 Nova Scotia Museum of Natural History, Undated.
Overview
Adjacent to the most densely populated area in the Gulf watershed, the Southern Coastal Shelf in all likelihood bears the heaviest impact from human activities of any area in the Gulf. Partially cut off from the Gulf of Maine proper by Stellwagen Bank, a shallow undersea plateau, the Southern Coastal Shelf is somewhat self-contained. Currents trap nutrients on the Southern Coastal shelf which support extensive marine productivity; but the same currents also trap contaminants emanating from a highly urbanized environment.
Surface area
3,183 mi2
Depth
Intertidal zone to ~100 m
Bathymetry including key features
The irregular bathymetry of the Southern Coastal Shelf was largely formed during glaciation: glaciers gouged the bottom and deposited sediments. As the ice melted, glacial features were reworked and eroded and larger rocks were deposited. With the return of the sea, erosion and redistribution of sediments occurred in a process that continues today.1 Two prominent features of the Southern Coastal Shelf are Stellwagen Bank, which is as shallow as 20 m in parts, and Stellwagen Basin, just west of the Bank, which reaches depths of 80 m.2,3
Substrate
Higher points of the Southern Coastal Shelf topography are characterized by coarse-grained sediments ranging from boulders and cobbles to sand. Deeper areas contain finer grained sediments such as silt and clay.4 Nor'easters are the predominant factor in the distribution of sediment types on the Southern Coastal Shelf. High winds create currents flowing in a southwesterly direction that winnow finer sediments from shoal areas and deposit them in the basins and on the trailing edges of banks.5
Relationship to large-scale circulatory patterns of the Gulf of Maine
A portion of the coastal current that flows southwestward along the Maine coast continues onto the Southern Coastal Shelf at Cape Ann (the other branch of the coastal current continues south along the edge of Wilkinson Basin). The degree of inflow from the coastal current is partly a function of the prevailing winds. Northeast winds increase the flow of water onto the shelf from the coastal current. Inflow of the coastal current, augmented in the spring by freshwater runoff from the Merrimack and other rivers to the north of Cape Ann, sets up a weak counterclockwise gyre over Massachusetts Bay and Cape Cod Bay. The current that is not entrained in the gyre exits the bays at the tip of Cape Cod where it continues in a southerly direction toward the Great South Channel.6,7,8
Information on average (seasonal/annual) oceanographic conditions
In the spring, currents on the Southern Coastal Shelf are characterized by a weak counter clockwise gyre over Massachusetts and Cape Cod Bays. In late spring and summer, circulation in Cape Cod Bay becomes isolated. Inflow of lower salinity water in the spring begins to stratify the water column; seasonal heating enhances stratification which remains in place until October when surface cooling leads to mixing. Storm events occasionally disrupt summer stratification. Primary productivity follows a pattern typical of coastal waters. Phytoplankton blooms occur in the spring when day length allows algal growth to take advantage of nutrient rich waters. As stratification sets in, nutrients in the upper sunlight layers are depleted. Primary and secondary production slows and decaying material becomes sequestered in bottom sediments. The onset of colder weather in the fall mixes nutrients back into the water column where the cycle starts again once sufficient sunlight is available to support plant growth. Three areas of the Southern Coastal Shelf are particularly productive. Boston Harbor and inner Cape Cod Bay support higher levels of production because their shallow waters allow recirculation of nutrients. Stellwagen Bank is productive because tidal forces in the Gulf keep the water over the Bank well mixed.9,10,11
Presence of GoMOOS buoy
There is one GoMOOS buoy on the Southern Coastal Shelf. Buoy A is located south of Cape Ann.
Whale abundance, distribution and migratory patterns
Cape Cod Bay, within the Southern Coastal Shelf, is designated as a "critical habitat area" for the right whale, designated as an endangered species by the National Oceanic and Atmospheric Administration. Right whales feed on plankton in Cape Cod and Massachusetts Bays during late winter and early spring.
In an earlier version of this map we did not distinguish between these two areas which we now divide at the 100 m isobath. The following description applies to both areas combined.
Overview
The Scotian Shelf is a very broad coastal shelf that extends from the coast of Nova Scotia to the edge of the continental slope. Approximately 60 miles wide at its southern extreme, near the Northeast Channel, the shelf broadens as it trends towards the northeast. Currents are characterized by a year-round, near-shore flow from the northeast to the southwest; it is known as the Nova Scotia Current. Influenced by the Gulf Stream to the south and the Labrador Current to the north, the waters of the Scotian Shelf support a wide variety of organisms. Tidal currents, seasonal cooling and upwelling related to bathymetric features return nutrients to sun-lit surface waters and contribute to the high productivity of shelf waters. The Scotian Shelf supports commercial fisheries for groundfish, lobsters and other species.3
Surface area
14,084 mi2
Depth
Intertidal to ~200 m
Bathymetry including key features
The bathymetry of the Scotian Shelf is marked by a broad trough, punctuated by a series of small, isolated banks, that runs the length of the shelf between the shallower coastal area and a series of large banks that mark the outer edge of the shelf. The most prominent of these large banks is Brown's Bank which forms the western terminus of the Scotian Shelf. 4,5
Substrate
The substrate of the Scotian Shelf varies according to its bathymetry: the banks are comprised of coarser sediments, such as sand and gravel, while the basins are characterized by finer-grained sediments such as clay. Boulders that dropped from the bottoms of melting glaciers occur occasionally. 6
Relationship to large-scale circulatory patterns of the Gulf of Maine
Currents flowing southwestwardly along the Scotian Shelf flow around the tip of Nova Scotia and contribute to the establishment of the counterclockwise gyre that characterizes currents in the Gulf of Maine. 7,8
Information on average (seasonal/annual) oceanographic conditions
On average, currents flow southwestardly along the Scotian Shelf. Derived from a mixture of St. Lawrence River outflow and Labrador currents, Scotian Shelf currents are are relatively fresh and cool. In the summer, shelf waters are stratified. Mixing occurs in the winter as surface waters cool and sink. Smaller scale oceanographic features, such as estuarine circulation, coastal upwelling, tidal fronts and shelf-break fronts, contribute to mixing of the shelf waters. 9
1 Cok, et al., 1965 2 Nova Scotia Museam of Natural History, Undated. 3 Nova Scotia Departments of Agriculture and Fisheries and Aquaculture, Undated 4 Nova Scotia Museam of Natural History, Undated. 5 Kostylev, et al., 2001 6 Nova Scotia Museam of Natural History, Undated. 7 Pettigrew, et al., 2005. 8 Xue, et al., 2000. 9 Nova Scotia Museum of Natural History, Undated.
Overview
Wilkinson Basin is one of three large basins in the Gulf of Maine.
Surface area
2,733 mi2
Depth
~270 m
Bathymetry including key features
Thick deposits of mud obscure the bathymetry of the underlying bedrock features in Wilkinson Basin.1 The surface of the bottom is featureless except for small mounds.2
Substrate
Wilkinson Basin is covered in thick deposits of mud.3,4 The sediment-water interface within Wilkinson Basin is characterized by a layer of turbid water that is tens of meters deep. The turbidity of due to the suspension of fine particles.5
Relationship to large-scale circulatory patterns of the Gulf of Maine
The counter clockwise gyre that circulates over Wilkinson Basin is fed in part by waters from the inner shelf of the eastern Gulf of Maine. While much of the eastern coastal current is deflected offshore near the mouth of Penobscot Bay, the waters of the inner shelf flow through into the western Gulf. Deflected offshore by the western coastal current, they contribute to the counter clockwise flow of currents in Wilkinson Basin.
Information on average (seasonal/annual) oceanographic conditions
The oceanography of Wilkinson Basin is characterized by a counter clockwise gyre. These currents are strongest in the spring and summer. It is estimated that the deep waters of the Gulf of Maine, such as in Wilkinson Basin, are replaced every 10-12 months.6
1 New England Fisheries Management Council, 2004 2 Valentine, 2002 3 New England Fisheries Management Council, 2004 4 Dorsey and Pederson, 1998 5 Pilskaln, et al., 1998 6 Xue, et al., 2000
Scotian Shelf, Browns Bank, Eastern Coastal Shelf, Great South Channel
Backus, R.H. (Ed.) 1987 Georges Bank. MIT Press, Cambridge, MA.
Baumgartner, M.F. and B.R. Mate. 2005. Summer and fall habitat of North Atlantic right whales (Eubalaena glacialis) inferred from satellite telemetry. Can. J. Fish. Aquat. Sci. 62: 527-543.
Blue Ocean Society for Marine Conservation. Undated. Research.
Cok, A.E., G. Drapeau, D. Grant, N. James, F. Medioli, N. Silverberg, and D.J. Stanley. 1965. Marine Geology Studies on the Scotian Shelf and Slope. Maritime Sediments 1 (4): 2-11.
Conkling, P. (Ed.). 1995. From Cape Cod to the Bay of Fundy. Cambridge, Mass.: MIT Press.
Desplanque, C. and D. Mossman. 2004. Tides and their seminal impact on the geology, geography, history, and socio-economics of the Bay of Fundy, eastern Canada. Atlantic Geology 40: 1-130.
Dorsey, E. M. and J Pederson (Eds.). 1998. Effects of Fishing Gear on the Sea Floor. Boston: Conservation Law Foundation.
Fader, G. 2004. Preface: Tides and their seminal impact on the geology, geography, history, and socio-economics of the Bay of Fundy, eastern Canada. Atlantic Geology 40: 1-130.
Kostylev, V.E., B.J. Todd, G.B.J. Fader, R.C. Courtney, G.D.M. Cameron, and R.A. Pickrill. 2001. Benthic habitat mapping on the Scotian Shelf based on multibeam bathymetry, surficial geology and seafloor photographs. Marine. Ecology progress Series 219: 121-137.
Moore, J.A. and M. Vecchione, B.B. Collette, R. Gibbons, K.E. Hartel, J.K. Galbraith, M. Turnipseed, M. Southworth, and E. Watkins. 2003. Biodiversity of Bear Seamount, New England Seamount Chain: Results of exploratory trawling. J. Northw. Atl. Fish. Sci., Vol. 31: 363-372.
Pettigrew, N.R., J.H. Churchill, C.D. Janzen, L.J. Mangum, R.P. Signell, A.C. Thomas, D.W. Townsend, J.P. Wallinga, and H. Xue. 2005. The kinematic and hydrographic structure of the Gulf of Maine Coastal Current. Deep-Sea Research II 52: 2369-2391.
Pilkskaln, C., J.H. Churchill and L. Mayer. 1998. Conservation Biology, Vol. 12, No. 6: 1223-1229.
Swift, D., B. Pelletier, A. Lyall, and J. Miller. 1969. Sediments of the Bay of Fundy - a preliminary report. Maritime Sediments: Vol. 5, No. 3: 95-100.
Thomas, A.C., D.W. Townsend, and R. Weatherbee. 2003. Satellite-measured phytoplankton variability in the Gulf of Maine. Continental Shelf Research 23: 971-989.
Woodward, C. 2004. The Lobster Coast: Rebels, Rusticators, and the Struggle for a Forgotten Frontier. Viking Press.
Xue, H., F. Chai, and N.R. Pettigrew. 2000. A model study of the seasonal circulation in the Gulf of Maine. Journal of Physical Oceanography 30:1111-1135.
