Sea ice

<p>Sea ice arises as <a href="/facts/Seawater/fRBJjbws">seawater</a> freezes. Because <a href="/facts/Ice/BGvkKFjD">ice</a> is less <a href="/facts/Density/92p6hh9I">dense</a> than water, it floats on the ocean's surface (as does <a href="/facts/Fresh_water/xMP2TxwI">fresh water</a> ice). Sea ice covers about 7% of the Earth's surface and about 12% of the world's oceans. Much of the world's sea ice is enclosed within the polar ice packs in the Earth's <a href="/facts/Polar_region/KkBuzr2n">polar regions</a>: the <a href="/facts/Arctic_ice_pack/M1ACdwEX">Arctic ice pack</a> of the <a href="/facts/Arctic_Ocean/l6HS3QyV">Arctic Ocean</a> and the <a href="/facts/Antarctic_ice_pack/YWp6Bunv">Antarctic ice pack</a> of the <a href="/facts/Southern_Ocean/F15W9ADT">Southern Ocean</a>. Polar packs undergo a significant yearly cycling in surface extent, a natural process upon which depends the <a href="/facts/Arctic_ecology/kd5p4yEM">Arctic ecology</a>, including the <a href="/facts/Arctic_sea_ice_ecology_and_history/VGfp3C54">ocean's ecosystems</a>. Due to the action of winds, currents and temperature fluctuations, sea ice is very dynamic, leading to a wide variety of ice types and features. Sea ice may be contrasted with <a href="/facts/Iceberg/2xFa1Xb2">icebergs</a>, which are chunks of <a href="/facts/Ice_shelf/63806X2Y">ice shelves</a> or <a href="/facts/Glacier/8GrKVUSS">glaciers</a> that <a href="/facts/Ice_calving/3xRnvKFs">calve</a> into the ocean. Depending on location, sea ice expanses may also incorporate icebergs.
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Sea ice open-in-new

Sea ice