Arctic Sea Ice
Between November and July each year, 15.5 million km² of Arctic Ocean freezes over – an area the size of Russia - covered in a slow moving mass of pack ice.
Icebergs differ from sea ice as they are formed from freshwater of glaciers, or frozen rivers, whereas sea ice is formed from frozen salt water.
Polar ice is hugely important to Earth’s oceans, as it regulates the heat balance and the salt-level balance of the seas.
In summer 2007, Arctic sea ice coverage fell to the lowest extent ever measured at the time; for the first time in recorded history the Northwest Passage opened.
Far from being a lifeless, frozen expanse, the Arctic sea ice contains a large and unique ecosystem that exists above, below and even inside the ice.
The Arctic sea ice provides a vital habitat for polar bears, seals, walruses and whales; the melting sea ice threatens their habitats and survival.