After last summer’s records in the Arctic Ocean, it was no surprise that ice formed slowly in the fall. We expected minimal ice formation in the Arctic Ocean through December, with most of the freezing to occur between January and March.
This is the month when ice formation should begin in earnest, and I expect it will, but in the early going, the NSIDC extent graph has been flat. Ice has been slowed by a persistent high pressure system in Siberia and associated low pressure system centered near the Laptev Sea, pushing warmer Atlantic-like conditions near the North Pole.
In the past, this unusual weather pattern might not have mattered, but with only about 11 weeks for ice to form, there is little chance to make up the loss of one or two weeks. Ice-watchers were already asking whether the 2013 Arctic winter ice would diverge from the patterns of the past, and every little delay makes that seem more likely.
You might expect the high level of northern hemisphere snow cover this month to help keep things cool, but that effect is brief and indirect. The fact that the sea ice halted at the same time that snow was on the ground in so much of North America and Asia shows that the snow cover doesn’t do much in the short run to support the sea ice.