Geoscience Reference
In-Depth Information
cloud cover throughout the year. For the central Arctic Ocean, mean
summer values of about 80 percent compare to winter values of typically
60 percent. Much of the summer cloud cover comprises low-level stratus.
2.1
The Arctic Ocean
2.1.1
Definition and Bathymetry
The Arctic Ocean covers an area of 14 million km
2
according to J. Welsh and his
colleagues (
1986
). But definitions of the Arctic Ocean and its various seas have
tended to be somewhat imprecise and/or arbitrary. Definition can be important,
however, in terms of determining the freshwater runoff from the Arctic lands into
the ocean and its effects on ocean salinity. Russian sources commonly divide the
Arctic Ocean into several climatic regions.
Figure 2.2
provides a breakdown from
Russian sources based more on geographic boundaries. In general usage, the term
Arctic Ocean would exclude at least the Bering and Greenland Seas, as well as the
Labrador Sea and Baffin Bay. The term “central Arctic Ocean” is very common in
the literature. A reasonable definition of the central Arctic Ocean is the region north
of all land areas that is covered year-round by sea ice (reviewed in the discussion
that follows). This is similar to the Russian term
Severnogo Ledovitnogo Okean
(northern ice-covered ocean).
The Arctic Ocean has limited connection to the world oceans (
Figure 2.3
) and is
therefore sometimes referred to as a Mediterranean-type sea. Depths vary greatly.
The narrow and shallow Bering Strait (separating Alaska from Russia) connects
the Arctic Ocean to the Pacific Ocean. The deeper Greenland and Norwegian seas
link it to the North Atlantic Ocean. There are also shallow passageways, with sills
85-140 m deep, through the Canadian Arctic Archipelago to Baffin Bay and the
Labrador Sea. The central Arctic Ocean comprises two major deep basins of more
than 3,000 m depth - the Amerasian (or Canada) and Eurasian basins, separated by
the Lomonosov Ridge.
Off most of North America, the continental shelf is narrow. In sharp contrast, off
Eurasia there is a series of broad shallow shelf seas - from west to east, the Barents,
Kara, Laptev, East Siberian and Chukchi seas. Almost half of the Arctic Ocean is
underlain by continental shelves (Johnson, Pogrebisky, and Macnab,
1994
). Water
depths are in the range of 120-230 m in the eastern Kara Sea, but only 20-30 m in
the Laptev Sea and the East Siberian Sea (Danilov,
2000
).
2.1.2
The Sea Ice Cover
The surface of the Arctic Ocean is characterized by its floating cover of sea ice.
The processes of sea ice growth, melt, circulation, and variability are discussed
at length in
Chapter 7
. As will become clear in the next few chapters, the sea ice
cover is intimately coupled with the atmospheric energy budget, the atmospheric
