Sunday, March 22, 2015

A Low Peak for Arctic Sea Ice

Arctic sea ice usually goes up and down in March, hitting its peak for the year somewhere along the way. This year, the peak was in February, and that day was followed by more than a week of rapid decline. The decline was so rapid that a similar period of regrowth has barely begun to make up for it, and with March now winding down, it is unlikely that any ice growth to come will revisit the earlier peak.

The details of timing of the ups and downs of ice in March have little lasting significance, but this March is noteworthy because ice levels were already tracking near record lows in February before they made their precipitous decline. The result is the lowest peak for Arctic ice ever recorded, followed by ice levels at record lows during March. Ice only declines from April through August, and this year, it has what looks like a two-week head start. This makes low ice levels at the late summer minimum more likely than they would have been after a near-normal March.

The decline in Arctic sea ice is one of the most prominent indications of global climate change, with the most definitive being the slow melting of permafrost, the underground ice that previously held together the land areas of the Arctic. Ice loss is also leading to a change in global shipping, with shipping routes across the Arctic Ocean open for several weeks every summer in recent years.