I | INTRODUCTION |
Arctic
Ocean, smallest of the five world oceans. The Arctic Ocean extends south
from the North Pole to the shores of Europe, Asia, and North America. See
also Arctic.
II | BOUNDARIES AND SIZE |
The surface waters of the Arctic Ocean mingle
with those of the Pacific Ocean through the Bering Strait, by way of a narrow
and shallow channel, which has a depth of 55 m (180 ft). More importantly, the
Arctic waters mix with those of the Atlantic Ocean across a system of submarine
sills (shallow ridges) that span the great distances from Scotland to
Greenland and from Greenland to Baffin Island at depths of 500 to 700 m (1,600
to 2,300 ft). Emptying into the Arctic Ocean are the Ob’, Yenisey, and Lena
rivers in Asia and the Mackenzie River in North America. The total surface area
of the Arctic Ocean is 14.1 million sq km (5.4 million sq mi). The major
subdivisions of the Arctic Ocean include the Norwegian, Barents, Kara, Laptev,
and Beaufort seas.
III | STRUCTURAL FEATURES |
Approximately one-third of the Arctic Ocean
is underlain by continental shelf, which includes a broad shelf north of Eurasia
and the narrower shelves of North America and Greenland. Seaward of the
continental shelves lies the Arctic Basin proper, which is subdivided into a set
of three parallel ridges and four basins (also known as deeps). These features
were discovered and explored beginning in the late 1940s. The Lomonosov Ridge,
the major ridge, cuts the Arctic Basin almost in half, extending as a submarine
bridge 1,800 km (1,100 mi) from Siberia to the northwestern tip of Greenland.
Parallel to it are two shorter ridges: the Alpha Ridge on the North American
side, defining the Canada and Makarov basins, and the Arctic Mid-Ocean Ridge on
the Eurasian side, defining the Nansen and Amundsen basins. The average depth of
the Arctic Ocean is only 1,300 m (4,300 ft) because of the vast shallow expanses
on the continental shelves. The deepest point in the Arctic Ocean is 5,450 m
(17,880 ft).
IV | ISLANDS |
The islands of the Arctic Ocean lie on the
continental shelves. To the northeast of Norway lies the archipelago of Svalbard
(formerly known as Spitsbergen); to the east are Franz Josef Land, Novaya
Zemlya, Severnaya Zemlya, the New Siberian Islands, and Wrangel Island, all of
which are located north of Russia. The numerous islands of the Canadian Arctic
Archipelago extend north and east from the Canadian mainland to Greenland, the
largest island of the Arctic Ocean.
V | ICE |
Three forms of ice are found in the Arctic
Ocean: land ice, river ice, and sea ice. Land ice enters the ocean in the form
of icebergs, which are created when pieces of glaciers break off. In the Arctic
Ocean, icebergs are created primarily along the coasts of Greenland. The
freezing of fresh water, and its subsequent transport into the ocean by rivers,
produces nearshore concentrations of river ice over small areas of the Siberian
and North American shelves. Sea ice is formed by the freezing of seawater. It is
the most extensive form of ice in the Arctic Ocean. In winter a permanent cap of
sea ice covers all of the ocean surface, except for the area northeast of
Iceland and north of Scandinavia. In summer the ice cover shrinks to expose
narrow bands of relatively open water along the coasts of most of Siberia,
Alaska, and Canada. The ice cap is composed of pack ice—that is, pieces of ice
that pile up and are pressed in ridges or hummocks that may be more than 10 m
(30 ft) in depth.
In 2005 scientists reported that the summer ice
cover had shrunk for the fourth consecutive year to its smallest extent since
1978 and probably to its smallest extent in 100 years. The report by scientists
from the National Snow and Ice Data Center and the National Aeronautics and
Space Administration (NASA) warned that global warming had played a role in the
decline. Using satellite data from NASA, scientists compared the Arctic sea ice
cover in September 2005, when Arctic sea ice usually reaches its minimum, with
the average extent of the sea ice cover since precise satellite measurements
were first obtained in 1978. They found that the ice cover had declined by 1.3
million sq km (500,000 sq mi), an area about twice the size of Texas. Using
other weather records, the scientists concluded that the total sea ice area of
5.3 million sq km (2 million sq mi) was probably the smallest in the last 100
years.
The scientists warned that the trend was not
only likely to continue but also to accelerate due to factors that include a
lack of winter recovery of sea ice, early onset of spring melting,
warmer-than-average temperatures, and an increase in areas of open ocean water,
which are dark and absorb solar radiation and therefore warm the area further.
The melting of Arctic sea ice could affect global climate, the scientists said,
because increased absorption of solar radiation warms the entire planet (see
Albedo). At the current rate of sea ice shrinkage, the scientists calculated
that the summer ice cover in the Arctic Ocean could disappear entirely by 2060.
Some scientists said the Arctic Oscillation, a natural cycle in the polar
atmosphere, could be a factor in the shrinkage of the ice cover, but there was a
reported consensus that global warming due to greenhouse gas emissions was also
involved.
In 2007 scientists announced that the melting
of summer sea ice had reached its greatest extent ever, encompassing a third of
the Arctic Ocean. Summer sea ice in September 2007 covered an area of 4.4
million sq km (1.7 million sq mi), down from 5.3 million sq km in September
2005. Some scientists said this meant that if the trend continued, the summer
sea ice cover would disappear altogether by 2030, rather than 2060. They further
predicted that winter ice recovery would probably not be complete during the
winter of 2007-2008 when the Arctic is in total darkness, leaving areas of open
ocean throughout the year.
VI | RESOURCES |
Fish, in commercially exploitable quantities,
are found only in the warmer marginal seas of the Arctic Ocean, notably in the
Barents Sea (primarily cod). Sea mammals, including various species of seal and
whale, were hunted to near extinction before being protected by quotas set
during the 1900s. Tin is actively mined off the coast of eastern Siberia.
Petroleum and natural gas are extracted north of Alaska and Canada. In 2007 the
United States Geological Survey (USGS) estimated that the ocean basin off
eastern Greenland may hold as much as 31.4 billion barrels of oil, natural gas,
and natural gas liquids in an area of 500,000 sq km (193,000 sq mi). The USGS
study of eastern Greenland is part of an effort to survey the entire Arctic for
oil and natural gas deposits known as the Circum-Arctic Resource Appraisal.
VII | SOVEREIGNTY ISSUES |
Five nations—Canada, Denmark, Norway,
Russia, and the United States—claim seabed rights in the Arctic Ocean. The
claims include rights to exploit subsurface minerals, oil and gas deposits, and
potentially useful bacteria. All five nations are signatories to the United
Nations Convention on the Law of the Sea. The treaty gives each nation rights to
exploit all natural resources within an area 370 km (200 nautical mi) off their
coastline.
In addition the treaty allows each nation to
claim an additional 278 km (150 nautical mi) of seabed if it can demonstrate
that its continental shelf extends that far. Under the treaty a nation must make
a formal claim to this additional area of seabed within ten years of ratifying
the treaty. As of 2007 only Norway and Russia had made a formal claim. Russia
maintains that the Lomonosov Ridge, a seabed feature that extends from Siberia
to Greenland, is part of its continental shelf.
With the warming of the Arctic Ocean and the
melting of sea ice, the competition for seabed rights has grown more acute as
nations contemplate the ability to explore for and exploit seabed resources,
especially oil and natural gas deposits. In 2007 Russia claimed sovereignty over
the North Pole, and Canada claimed sovereignty over the Northwest Passage. In
addition, Denmark sent a geological expedition to the Arctic to determine the
extent of the continental shelf below Greenland, a self-governing part of
Denmark. A successful claim to the North Pole would allow a country to set
environmental standards and regulate maritime traffic.
The United States disputes Canada’s claim to
the Northwest Passage sea route, which could be open to maritime traffic
year-round by 2030. The route would considerably shorten the distance between
Europe and Asia for ships that presently transit the Panama Canal.
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