240
Andrew CLARKE
deep sea. Of particular significance were the studies in
the Southern Ocean.
The expeditions that followed are relatively well
known [see Gage and Tyler (1991) for a brief historical
summary]. Their results are widely available through
the comprehensive and thorough expedition reports.
In contrast the enormous volume of data from the
extensive investigations of the deep sea by biologists
of the former Soviet Union are almost unknown in
the west. Until recently, they were largely available
only in Russian; but the appearance in mainstream
western literature of major reviews is now revealing
the wealth of knowledge of the deep sea that had
been accumulated, including extensive work in polar
regions (see, for example, Gebruk et al., 1997). It
is likely that the merging of these results with more
recent investigations, such as those of USNS Eltanin,
and German work from RV Polarstern, will result in
significant advances in understanding of the biology of
the polar deep seas. A succinct history of research in
this area has been given by Vinogradova (1997).
THE ARCTIC DEEP SEAS
There have always been difficulties in defining the Arctic marine ecosystem. These difficulties are particularly
acute for benthic systems in both pelagic and shallowwater environments, where truly polar conditions and
assemblages merge gradually into those of boreal and
cold-temperate regions.
The Arctic deep-sea environment is, however, fairly
precisely circumscribed. It consists of a series of
deep basins, isolated from all other deep waters by
large areas of shallow sea, and crossed by a series
of ridges (Fig. 8.1). We probably know less of the
topography of the Arctic than any other ocean basin
because the extensive cover of multi-year ice prevents
the use of many traditional techniques for determining
bathymetry. As a result the names of some of the
smaller basins have only recently stabilised, resulting in
confusion for biologists researching the older literature.
Recent oceanographic studies of the circulation of
intermediate depth waters (Rudels et al., 1994) have,
however, suggested that functionally there are three
major deep water basins (Fig. 8.2).
Traditionally the Arctic has been viewed as consisting of two large basins, the Eurasian and Amerasia
Basins, separated by the vast submarine mountain range
of the Lomonosov Ridge. Each of these basins is itself
divided by ridges (Fig. 8.1). The Amerasia Basin is
crossed by the Alpha- and Mendeleev Ridges, which
separate the large Canada Basin and the smaller but
deeper Makarov Basin. The Alpha–Mendeleev Ridge is
the largest submarine mountain complex in the Arctic
Ocean, exceeding the Alps in extent. The Eurasian
Basin is divided by the Nansen–Gakkel Ridge. This
mid-ocean ridge separates the very deep Fram (or
Amundsen) Basin from the Nansen Basin. It would
appear that the initiation of sea-floor spreading along
this ridge transported the Lomonosov Ridge, originally
part of the Barents and Kara shelves, to its present
position (Weber, 1989).
Surrounding these deep basins are wide and relatively shallow continental shelves. Of particular ecological importance are the series of five epicontinental seas
located on the huge European and Siberian continental
shelves: the Barents, Kara, Laptev, East Siberian and
Chukchi Seas (Fig. 8.1).
All the Arctic basins are deep, typically exceeding
3000 m, and all contain large areas of very flat abyssal
plain. Although the deep Arctic basins are isolated from
the Pacific Ocean by the broad shallow continental
shelves of the Chukchi Sea and the Bering Strait,
there is an important deep-water connection through
Fram Strait to the deep waters of the Norwegian Sea
(Fig. 8.1). The Norwegian Sea is itself separated from
the deep North Atlantic by ridges covered by shallower
water, running east–west from Greenland to Iceland
(the Denmark Strait) and thence to Norway. This
topography indicates that the Arctic deep sea cannot
be completely prescribed, and that the faunal history
of the Norwegian Sea is of considerable significance
in understanding the evolutionary history of the fauna
of the Arctic basin.
Large-scale oceanography
The topography of the Arctic basin restricts exchange
with lower-latitude oceans to two connections, through
the very shallow Bering Strait to the Pacific, and
through the deeper Fram Strait to the Greenland–
Iceland–Norwegian Sea. Zenkevitch (1963) compared
the dimensions of these two connections, and estimated
the mean annual transport through them as 0.25 Sv
through the Bering Strait and ~13 Sv from the North
Atlantic. Lewis (1982) computed an overall water, salt
and heat budget for the Arctic Basin (Table 8.1). This
budget incorporated freshwater inflow from rivers, and
outflow of ice, both of which fluxes were small in
Andrew CLARKE
deep sea. Of particular significance were the studies in
the Southern Ocean.
The expeditions that followed are relatively well
known [see Gage and Tyler (1991) for a brief historical
summary]. Their results are widely available through
the comprehensive and thorough expedition reports.
In contrast the enormous volume of data from the
extensive investigations of the deep sea by biologists
of the former Soviet Union are almost unknown in
the west. Until recently, they were largely available
only in Russian; but the appearance in mainstream
western literature of major reviews is now revealing
the wealth of knowledge of the deep sea that had
been accumulated, including extensive work in polar
regions (see, for example, Gebruk et al., 1997). It
is likely that the merging of these results with more
recent investigations, such as those of USNS Eltanin,
and German work from RV Polarstern, will result in
significant advances in understanding of the biology of
the polar deep seas. A succinct history of research in
this area has been given by Vinogradova (1997).
THE ARCTIC DEEP SEAS
There have always been difficulties in defining the Arctic marine ecosystem. These difficulties are particularly
acute for benthic systems in both pelagic and shallowwater environments, where truly polar conditions and
assemblages merge gradually into those of boreal and
cold-temperate regions.
The Arctic deep-sea environment is, however, fairly
precisely circumscribed. It consists of a series of
deep basins, isolated from all other deep waters by
large areas of shallow sea, and crossed by a series
of ridges (Fig. 8.1). We probably know less of the
topography of the Arctic than any other ocean basin
because the extensive cover of multi-year ice prevents
the use of many traditional techniques for determining
bathymetry. As a result the names of some of the
smaller basins have only recently stabilised, resulting in
confusion for biologists researching the older literature.
Recent oceanographic studies of the circulation of
intermediate depth waters (Rudels et al., 1994) have,
however, suggested that functionally there are three
major deep water basins (Fig. 8.2).
Traditionally the Arctic has been viewed as consisting of two large basins, the Eurasian and Amerasia
Basins, separated by the vast submarine mountain range
of the Lomonosov Ridge. Each of these basins is itself
divided by ridges (Fig. 8.1). The Amerasia Basin is
crossed by the Alpha- and Mendeleev Ridges, which
separate the large Canada Basin and the smaller but
deeper Makarov Basin. The Alpha–Mendeleev Ridge is
the largest submarine mountain complex in the Arctic
Ocean, exceeding the Alps in extent. The Eurasian
Basin is divided by the Nansen–Gakkel Ridge. This
mid-ocean ridge separates the very deep Fram (or
Amundsen) Basin from the Nansen Basin. It would
appear that the initiation of sea-floor spreading along
this ridge transported the Lomonosov Ridge, originally
part of the Barents and Kara shelves, to its present
position (Weber, 1989).
Surrounding these deep basins are wide and relatively shallow continental shelves. Of particular ecological importance are the series of five epicontinental seas
located on the huge European and Siberian continental
shelves: the Barents, Kara, Laptev, East Siberian and
Chukchi Seas (Fig. 8.1).
All the Arctic basins are deep, typically exceeding
3000 m, and all contain large areas of very flat abyssal
plain. Although the deep Arctic basins are isolated from
the Pacific Ocean by the broad shallow continental
shelves of the Chukchi Sea and the Bering Strait,
there is an important deep-water connection through
Fram Strait to the deep waters of the Norwegian Sea
(Fig. 8.1). The Norwegian Sea is itself separated from
the deep North Atlantic by ridges covered by shallower
water, running east–west from Greenland to Iceland
(the Denmark Strait) and thence to Norway. This
topography indicates that the Arctic deep sea cannot
be completely prescribed, and that the faunal history
of the Norwegian Sea is of considerable significance
in understanding the evolutionary history of the fauna
of the Arctic basin.
Large-scale oceanography
The topography of the Arctic basin restricts exchange
with lower-latitude oceans to two connections, through
the very shallow Bering Strait to the Pacific, and
through the deeper Fram Strait to the Greenland–
Iceland–Norwegian Sea. Zenkevitch (1963) compared
the dimensions of these two connections, and estimated
the mean annual transport through them as 0.25 Sv
through the Bering Strait and ~13 Sv from the North
Atlantic. Lewis (1982) computed an overall water, salt
and heat budget for the Arctic Basin (Table 8.1). This
budget incorporated freshwater inflow from rivers, and
outflow of ice, both of which fluxes were small in