Atlantic Polar Biome
133
anomalous average depth, close to 200 m, with a shelf break occurring at around 400 m.
The Labrador shelf is also anomalous for the deep troughs that lie about 70 km offshore
and parallel to the coast, for about 550 km north and south of the Strait of Belle Isle.
Hudson Bay requires special comment for it is really a very shallow inland sea, of more
than one million square kilometers in area, having a mean depth of around 150 m. It is
also remarkable that the Hudson Bay region is still rising because of eustatic rebound in
our postglacial period, by as much as 1 m y
−1 , resulting in a continually evolving, young
coastline.
Along the eastern coast of Greenland, the shelf is unusually deep, so that the 200-m
contour lies close to the steep-to coastline, with a shelf break at 400 m offshore. To the
west of Cape Farewell (60
N), the shelf is narrower but shoaler, having a break of slope
at 200 m. This section of the Greenland shelf occupies a significant part of the entire
width of Davis Strait (65
N).
Defining Characteristics of Regional Oceanography
Here, at the top of the world, seasonal cycles of irradiance are extreme and the perpetually
low temperatures induce almost complete ice coverage of the Arctic Ocean year-round,
and of its marginal basins in winter. Another, often overlooked, consequence of such
high latitudes is the extreme value taken by the Coriolis parameter, and the effect of this
on water motion and especially on shelf-break tidal regimes.
Arctic continental shelves generally have a complex density circulation, behaving as
salt-wedge estuaries in summer and, by the deep export of salt-rejection brine produced
as the sea freezes, as negative estuaries in winter. Thus, the surface water of the continental
shelves is more dilute and shows greater seasonal salinity variation than that of the central
part of the Arctic Ocean (Carmack, 1990). The Laptev and East Siberian Seas along
the northern coast of Asia carry particularly heavy effluents from the Lena, Kolyma,
and Indigirka Rivers that drain the north Siberian plains. Hudson Bay has a cyclonic
circulation, driven by buoyancy and wind forcing; near-surface low-salinity water passes
out of the embayment to be exchanged with deeper water of higher salinity.
The Arctic Ocean is dominated by the Circumpolar Boundary Current, within which
major water mass transformation occurs. This circulation is initiated by a flow of warm
North Atlantic water that enters the Arctic Ocean through the eastern Greenland Sea (see
SARC Province) to pass around northern Norway and through the Bear Island Channel.
Most recirculates within the Greenland Sea before entering the Barents Sea, but some
passes on eastward and so enters the anticlockwise circulation of the boundary current
that circles the basin along the edge of the wide shelf of northern Russia and the narrower
shelf of north America and Greenland. The source for Arctic Ocean surface water is
mainly the warm Atlantic Current, which is progressively modified at high latitudes by
heat flux to the atmosphere, river runoff, and meltwater in summer and by salt rejection
during freezing in winter (Jones et al., 1990). These processes induce both a buoyant
surface layer and a dense and highly saline bottom layer over the shelf regions. The
1994 section by Canadian and U.S. icebreakers confirmed the continuity right across the
Arctic Ocean of the thermocline lying at about 110 m between surface water of −12
to
−17
C, with warmer water of 0.2 to 10
C below. With this is associated a nitracline
above which both nitrate and silicate are reduced to very low levels in summer.
The main flow of the boundary current leaves the Arctic Ocean through Fram Strait and
this is the source of the narrow, buoyancy-forced East Greenland Current, whose seaward
boundary is the strongly marked East Greenland Polar Front, a temperature discontinuity
that defines the outer boundary of BPLR in the warmer Nordic Sea water (Muench, 1990).
The southerly East Greenland Current, locked to topography, is continuous along the
coast as far as Cape Farewell, which turns the flow up the west coast. Here, the province is
133
anomalous average depth, close to 200 m, with a shelf break occurring at around 400 m.
The Labrador shelf is also anomalous for the deep troughs that lie about 70 km offshore
and parallel to the coast, for about 550 km north and south of the Strait of Belle Isle.
Hudson Bay requires special comment for it is really a very shallow inland sea, of more
than one million square kilometers in area, having a mean depth of around 150 m. It is
also remarkable that the Hudson Bay region is still rising because of eustatic rebound in
our postglacial period, by as much as 1 m y
−1 , resulting in a continually evolving, young
coastline.
Along the eastern coast of Greenland, the shelf is unusually deep, so that the 200-m
contour lies close to the steep-to coastline, with a shelf break at 400 m offshore. To the
west of Cape Farewell (60
N), the shelf is narrower but shoaler, having a break of slope
at 200 m. This section of the Greenland shelf occupies a significant part of the entire
width of Davis Strait (65
N).
Defining Characteristics of Regional Oceanography
Here, at the top of the world, seasonal cycles of irradiance are extreme and the perpetually
low temperatures induce almost complete ice coverage of the Arctic Ocean year-round,
and of its marginal basins in winter. Another, often overlooked, consequence of such
high latitudes is the extreme value taken by the Coriolis parameter, and the effect of this
on water motion and especially on shelf-break tidal regimes.
Arctic continental shelves generally have a complex density circulation, behaving as
salt-wedge estuaries in summer and, by the deep export of salt-rejection brine produced
as the sea freezes, as negative estuaries in winter. Thus, the surface water of the continental
shelves is more dilute and shows greater seasonal salinity variation than that of the central
part of the Arctic Ocean (Carmack, 1990). The Laptev and East Siberian Seas along
the northern coast of Asia carry particularly heavy effluents from the Lena, Kolyma,
and Indigirka Rivers that drain the north Siberian plains. Hudson Bay has a cyclonic
circulation, driven by buoyancy and wind forcing; near-surface low-salinity water passes
out of the embayment to be exchanged with deeper water of higher salinity.
The Arctic Ocean is dominated by the Circumpolar Boundary Current, within which
major water mass transformation occurs. This circulation is initiated by a flow of warm
North Atlantic water that enters the Arctic Ocean through the eastern Greenland Sea (see
SARC Province) to pass around northern Norway and through the Bear Island Channel.
Most recirculates within the Greenland Sea before entering the Barents Sea, but some
passes on eastward and so enters the anticlockwise circulation of the boundary current
that circles the basin along the edge of the wide shelf of northern Russia and the narrower
shelf of north America and Greenland. The source for Arctic Ocean surface water is
mainly the warm Atlantic Current, which is progressively modified at high latitudes by
heat flux to the atmosphere, river runoff, and meltwater in summer and by salt rejection
during freezing in winter (Jones et al., 1990). These processes induce both a buoyant
surface layer and a dense and highly saline bottom layer over the shelf regions. The
1994 section by Canadian and U.S. icebreakers confirmed the continuity right across the
Arctic Ocean of the thermocline lying at about 110 m between surface water of −12
to
−17
C, with warmer water of 0.2 to 10
C below. With this is associated a nitracline
above which both nitrate and silicate are reduced to very low levels in summer.
The main flow of the boundary current leaves the Arctic Ocean through Fram Strait and
this is the source of the narrow, buoyancy-forced East Greenland Current, whose seaward
boundary is the strongly marked East Greenland Polar Front, a temperature discontinuity
that defines the outer boundary of BPLR in the warmer Nordic Sea water (Muench, 1990).
The southerly East Greenland Current, locked to topography, is continuous along the
coast as far as Cape Farewell, which turns the flow up the west coast. Here, the province is