148
Chapter 9: The Atlantic Ocean
the light field and the shoaling of Z m but, after June, P tracks the declining light field.
Accumulation of chlorophyll tracks changes in rate of P until late summer, after which
a secondary accumulation of biomass occurs in September–October and is interpreted
as a response to the descent of herbivores to overwintering depths. Balance between
production and consumption may be closer than in BPLR.
Atlantic Subarctic Province (SARC)
Extent of the Province
From above the Rejkanes Ridge, southeast of Iceland, this province extends to the northwest, including the entire Norwegian Sea and the southern Barents Sea as far as Novaya
Zemlya. The province is bounded to the north by the Arctic Front (or OPF), beyond
which is the ARCT province. In the Barents Sea the adjacent province is BPLR, from
which SARC is divided by the well-marked thermal front between Arctic and Atlantic
water that passes close around Bear Island and meanders eastward from Hope Island at
about 74–78
N. Between SARC and NECS an effective boundary is the break of slope
between the Shetlands and the Faeroes. In the south, an arbitrary line at 60
N separates
the SARC portion of the North Atlantic Drift from that lying in NADR.
Continental Shelf Topography and Tidal and Shelf-edge Fronts
For the same reason that the coast of Greenland and the shelves of the Arctic Ocean were
included in the BPLR province, the coast of Norway, from Stavanger to the North Cape,
is included in this province; this coast is very steep-to with a very narrow terrace across
which many troughs extend the topography of fjords. Only at the Lofoten Bank (68
N)
is there any significant shelf width. The Barents Sea is nowhere deeper than 500 m; the
eastern half, associated with Hope and Bear Islands and Spitzbergen, is <200 m deep and
is one of the wider shelf regions in any sea. The Faeroes and Iceland lie on small 200-m
platforms arising from oceanic depths.
The Faeroe platform carries a coastal water mass, which is confined within a persistent
tidal front that surrounds the archipelago at a depth of about 150 m. A Norwegian Coastal
Front lies outside the northward flow of the permanently stabilized water mass of low
salinity of the coastal current (see later discussion), following the break of slope; it thus
has the character of a shelf-edge front. Tidal amplitude increases northward along the
Norwegian coast from a few centimeters to >1 m at North Cape; in fjords and narrow
straits in the more polar regions, then, very strong tidal streams may be expected, with
all that they entail.
Defining Characteristics of Regional Oceanography
This is a complex oceanographic region, especially in the north, where warm Atlantic
water penetrates into very high latitudes indeed: it has no equivalent in the Pacific Ocean.
This flow is highly variable between years, forcing strong variability in both physical and
ecological processes.
South of Iceland, part of the North Atlantic Current begins to flow toward the Nordic
seas rather than continuing eastward in the gyral circulation. It is here that Atlantic
subtropical water begins its odyssey toward the Arctic Ocean, penetrating even into the
Kara Sea (Dickey et al., 1994). This flow exists both as a broad west wind drift, and also
as a jet current along the Oceanic Polar Front (OPF) whose characteristics were described
in the previous section, and which forms the northwest boundary of SARC, separating
Atlantic water from Arctic water. The eastward zonal flow to the south of the OPF passes
across the Iceland-Faeroes Ridge to the south of the Iceland Gap Front (Johannessen,
Chapter 9: The Atlantic Ocean
the light field and the shoaling of Z m but, after June, P tracks the declining light field.
Accumulation of chlorophyll tracks changes in rate of P until late summer, after which
a secondary accumulation of biomass occurs in September–October and is interpreted
as a response to the descent of herbivores to overwintering depths. Balance between
production and consumption may be closer than in BPLR.
Atlantic Subarctic Province (SARC)
Extent of the Province
From above the Rejkanes Ridge, southeast of Iceland, this province extends to the northwest, including the entire Norwegian Sea and the southern Barents Sea as far as Novaya
Zemlya. The province is bounded to the north by the Arctic Front (or OPF), beyond
which is the ARCT province. In the Barents Sea the adjacent province is BPLR, from
which SARC is divided by the well-marked thermal front between Arctic and Atlantic
water that passes close around Bear Island and meanders eastward from Hope Island at
about 74–78
N. Between SARC and NECS an effective boundary is the break of slope
between the Shetlands and the Faeroes. In the south, an arbitrary line at 60
N separates
the SARC portion of the North Atlantic Drift from that lying in NADR.
Continental Shelf Topography and Tidal and Shelf-edge Fronts
For the same reason that the coast of Greenland and the shelves of the Arctic Ocean were
included in the BPLR province, the coast of Norway, from Stavanger to the North Cape,
is included in this province; this coast is very steep-to with a very narrow terrace across
which many troughs extend the topography of fjords. Only at the Lofoten Bank (68
N)
is there any significant shelf width. The Barents Sea is nowhere deeper than 500 m; the
eastern half, associated with Hope and Bear Islands and Spitzbergen, is <200 m deep and
is one of the wider shelf regions in any sea. The Faeroes and Iceland lie on small 200-m
platforms arising from oceanic depths.
The Faeroe platform carries a coastal water mass, which is confined within a persistent
tidal front that surrounds the archipelago at a depth of about 150 m. A Norwegian Coastal
Front lies outside the northward flow of the permanently stabilized water mass of low
salinity of the coastal current (see later discussion), following the break of slope; it thus
has the character of a shelf-edge front. Tidal amplitude increases northward along the
Norwegian coast from a few centimeters to >1 m at North Cape; in fjords and narrow
straits in the more polar regions, then, very strong tidal streams may be expected, with
all that they entail.
Defining Characteristics of Regional Oceanography
This is a complex oceanographic region, especially in the north, where warm Atlantic
water penetrates into very high latitudes indeed: it has no equivalent in the Pacific Ocean.
This flow is highly variable between years, forcing strong variability in both physical and
ecological processes.
South of Iceland, part of the North Atlantic Current begins to flow toward the Nordic
seas rather than continuing eastward in the gyral circulation. It is here that Atlantic
subtropical water begins its odyssey toward the Arctic Ocean, penetrating even into the
Kara Sea (Dickey et al., 1994). This flow exists both as a broad west wind drift, and also
as a jet current along the Oceanic Polar Front (OPF) whose characteristics were described
in the previous section, and which forms the northwest boundary of SARC, separating
Atlantic water from Arctic water. The eastward zonal flow to the south of the OPF passes
across the Iceland-Faeroes Ridge to the south of the Iceland Gap Front (Johannessen,