The Arctic is exhibiting characteristics indicative of the well-documented long-term warming trend over the past 100 years. After reaching the second lowest areal extent back in September, the Arctic ice sheet underwent a rapid re-forming process. With no sunlight and sub-freezing temperatures, that was to be expected. But that’s not the whole story. In the past two years, atmospheric conditions have shifted from long-term states to a new state that has allowed more warm air and water to encroach above the Arctic Circle (I’ll write a more extensive post on this another time). That anomalously warm water has released a lot of energy back into the atmosphere, adding to the latent heat released by freezing water. The result? Arctic sea ice formation has temporarily stalled, as seen in the following time series:
Currently, temperatures in the Arctic north of Canada are 6C warmer than the climatological average. That large anomaly is indicative of just how much heat was transported to the pole this year. As you can see from the graph, areal ice extent in 2008 is now lower than it was at the same time in 2007. It is also well below the climatological norm. Here is how the ice extent looks to satellites:
This picture shows another reason why the rapid growth of new ice has stalled: there is much less space to expand to than there was in October. The area between Greenland and Scandinavia and Greenland and Canada will of course see additional ice growth. The ice will also grow into the Pacific south of Alaska and Russia. But those regions contain less area than the area that saw refreezing in October.
With the passing of the Winter Solstice, the sun will begin shining over more area in the Northern Hemisphere every day again through June. The Arctic ice sheet will likely grow through March before remelting again next year. What will the maximum extent of ice in 2008-09 be? The long-term health of ice sheets and glaciers is not good in the face of multi-degree positive temperature anomalies.
billlaurelMD posted a similar diary at a later date – the graph in his diary demonstrates that the phenonema described above have continued.