Sunday, July 17, 2011

Arctic Sea Ice in Record-Breaking Decline

After a spring season of near-record ice melt in the Arctic Ocean, the Arctic ice extent map has moved into record territory again this month. Ice extent is declining several days ahead of the previous record season of 2007, and six weeks ahead of the long-term average. Arctic ice melt in recent years has been very much affected by the weather, but not so this year — major swings in the Arctic weather patterns have barely perturbed the extent graph’s downward trend. The graph is smoother than in a typical year. Statistically, a smooth graph may be the result of many small, independent effects, and that may be what is going on with the Arctic ice, which is thinner than ever before seen and has broken into small pieces, a pattern we are not used to seeing.

The current weather pattern is one that historically is not so favorable for ice melt, but instead is associated with an unusually high flow of ice from the Arctic Ocean into the Atlantic Ocean along both coasts of Greenland. In spite of that, the map seems to show continued rapid melt and not so much ice flowing out. Perhaps with the unusually thin ice, much of it is melting before it reaches the area of Greenland. With the ice broken in smaller pieces, perhaps there is nothing to clog up the flow of ice, so that it no longer matters which way the wind blows. Or with so much open water between the ice, the water is absorbing more sunlight and may already be warm enough to make the week-to-week weather fluctuations irrelevant.

But if the ice melt is no longer responding to the weather, then there is nothing to stop a new record low ice extent from occurring, conceivably as early as four weeks from now. If the melt were to continue on the straight line of the last two weeks, all the ice would melt away before the sun went away in September. Realistically, the melt will slow down at some point, but the warmer the ocean becomes, the later that will occur. With more surface water exposed to the sun than in any previous July, the Arctic Ocean must be warming faster than in any previous July. The current conditions, with thin, free-flowing ice covering such a small area this early in the season, have never before been observed, so we don’t know what might happen.