The Arctic: The Smallest Ocean, and Far From Barren

The Arctic is the smallest of the world's five ocean basins — and it is still about 1.5 times as big as the United States, with an area of about 6.1 million square miles. It is almost completely covered in ice for most of the year, and its average temperature seldom rises above freezing. Yet it is anything but barren.

A polar bear walks on the frozen surface of the Arctic Ocean. Credit: NOAA.

The basin

The Arctic Ocean is bordered by Greenland, Canada, Norway, Alaska and Russia. Its average depth is 3,953 feet, and at its deepest point it reaches 18,264 feet.

Life in and under the ice

• Inside the ice. Tunnels in sea ice called brine channels hold bacteria and algae, which feed flatworms and other tunnel-dwellers.
• On top of the ice. Melting ice forms ponds on the surface that grow into biological communities.
• Under the ice. When the ice melts, it releases organisms and nutrients into the water, and algae grow beneath the ice.

A food web from algae to bears

The algae under the ice feed tiny zooplankton, which feed fish, squid, seals and whales. Some of those larger animals are in turn hunted by the polar bears that live on the ice. When creatures under the ice die, they sink to the bottom and nourish sponges, sea anemones and other bottom-dwellers — and as those communities grow, they feed seals, fish and whales once again.

Sources

Based on "What is the world's smallest ocean?" from NOAA's National Ocean Service, a work of the United States government in the public domain.