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Sunset over sea ice off the coast of Antarctica captured from the Nathaniel B. Palmer, an NSF research icebreaker ship, during an Antarctic oceanography research cruise.
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NOAA Corp Collection, Photographer Michael Van Woert

Polar Oceans

There are two oceans in Earth's polar regions.

The oceans that are in the polar regions are a bit different from other oceans on Earth. There is often sea ice at their surface, especially during the winter months. And those chilly waters are home to some unique marine life.

Seawater from polar regions can be denser than seawater from other places. This is because seawater in the polar oceans is cold, and this makes it denser. It can also become saltier than other seawater during the winter when sea ice freezes at the ocean surface removing some of the freshwater to make the ice, which concentrates the salts. The denser seawater sinks to the bottom of the ocean. It travels out of the polar regions in slow currents that travel around the bottom of the world’s oceans as part of the pattern of global ocean circulation called thermohaline circulation.

The polar oceans are warming up as Earth’s climate changes. Scientists are studying how the polar oceans, the sea ice at their surface, and the marine life within them, are changing in response to recent climate change. They have found that sea ice in the Arctic Ocean is melting so quickly that by the year 2040 there may not be any sea ice in the Arctic during summer months. The melting sea ice threatens Arctic Ocean species such as polar bears. In the Antarctic, scientists are studying the effect of less sea ice on the penguin breeding season.

If it gets warm enough that polar oceans are warmer and sea ice no longer forms, the seawater would not be as dense and would not flow down to the ocean bottom, potentially slowing or stopping global ocean circulation. If the oceans stopped their pattern of global circulation, many aspects of our planet would change including regional climates, the severity of weather events, and marine ecosystems.

Last modified June 18, 2007 by Lisa Gardiner.

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The Spring 2010 issue of The Earth Scientist, focuses on the ocean, including articles on polar research, coral reefs, ocean acidification, and climate. Includes a gorgeous full color poster!

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