There has been an unprecedented heat wave in boreal circumpolar landmasses this winter (yes, even while the Polar Vortex was freezing the hell out of the temperate zones of N America). The result is that Arctic rivers in Alaska, Canada and Siberia have been dumping a lot of warm water into the Arctic basin.

http://www.nasa.gov/jpl/news/arctic-sea-ice-melt-20140305/#.U0BAj6hdVA1

This Arctic process contrasts starkly with those that occur in Antarctica, a frozen continent without any large rivers. The sea ice cover in the Southern Ocean surrounding Antarctica has been relatively stable, while Arctic sea ice has been declining rapidly over the past decade.

“River discharge is a key factor contributing to the high sensitivity of Arctic sea ice to climate change,” said Nghiem. “We found that rivers are effective conveyers of heat across immense watersheds in the Northern Hemisphere. These watersheds undergo continental warming in summertime, unleashing an enormous amount of energy into the Arctic Ocean, and enhancing sea ice melt. You don’t have this in Antarctica.”

Nifty Peekaboo Slider Graphic

In the Antarctic, however, the river water is all just above freezing, or in the case of glaciers, well below.