Ice

Permafrost across the North, and the retreat of Arctic sea ice

Two of the clearest signs of a warming North are shown in our ice: the frozen ground beneath much of the country and the sea ice on the Arctic Ocean are both in decline.

Permafrost

Much of the North sits on permafrost. This is ground that stays frozen year-round. It grades from continuous permafrost across the High Arctic (frozen almost everywhere) to isolated patches near its southern limit. The classic national map below shows those zones. Note that it reflects mapping from the mid-1990s, and permafrost extent has been retreating as the climate warms. The southern boundary today sits further north.

Arctic sea ice

The clearest single signal of a warming North is the decline of Arctic sea ice. Its extent oscillates with the seasons, peaking in March and reaching its lowest extent in September. The September minimum has fallen by more than a third since satellite records began in 1979. Canada’s Arctic waters, including parts of the Northwest Passage, are increasingly ice-free at the end of summer.

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