Arctic ocean
The Arctic Ocean is the smallest and shallowest of the world's
five major oceans.[1] It spans an area of approximately 14,060,000
km2 (5,430,000 sq mi) and is known as the coldest of all the
oceans. The International Hydrographic Organization (IHO)
recognizes it as an ocean, although some oceanographers call it
the Arctic Mediterranean Sea.[2] It has been described
approximately as an estuary of the Atlantic Ocean.[3][4] It is
also seen as the northernmost part of the all-encompassing World
Ocean. The Arctic Ocean includes the North Pole region in the
middle of the Northern Hemisphere and extends south to about 60°N.
The Arctic Ocean is surrounded by Eurasia and North America, and
the borders follow topographic features: the Bering Strait on the
Pacific side and the Greenland Scotland Ridge on the Atlantic
side. It is mostly covered by sea ice throughout the year and
almost completely in winter. The Arctic Ocean's surface
temperature and salinity vary seasonally as the ice cover melts
and freezes;[5] its salinity is the lowest on average of the five
major oceans, due to low evaporation, heavy fresh water inflow
from rivers and streams, and limited connection and outflow to
surrounding oceanic waters with higher salinities. The summer
shrinking of the ice has been quoted at 50%.[1] The US National
Snow and Ice Data Center (NSIDC) uses satellite data to provide a
daily record of Arctic sea ice cover and the rate of melting
compared to an average period and specific past years, showing a
continuous decline in sea ice extent.[6] In September 2012, the
Arctic ice extent reached a new record minimum. Compared to the
average extent (1979–2000), the sea ice had diminished by 49%.[7]