|September 16, 2009|
Updates on Warm Seas and Arctic Ice
The National Climatic Data Center has released its review of worldwide sea surface temperatures for August and for the stretch from June through August and finds that both the month and the "summer" (as looked at from the Northern Hemisphere) were the warmest at least since 1880, when such records were first systematically compiled.
Sea ice in the Arctic appears to be starting the slow late-summer freeze after reaching its minimum extent several days ago, by a couple of estimates (National Snow and Ice Data Center; International Arctic Research Center / Japan Aerospace Exploration Agency). Here's the global sea ice trend, combining what's going on up north and down south. This season's Arctic ice retreat ranks well behind the extraordinary ice retreat of 2007 and also last year's but remains below the average ice extent for the stretch since 1979, when satellites started monitoring Arctic conditions with some precision. Here's a compilation of various groups' experimental ice forecasts for this year and the results.
The National Oceanic and Atmospheric Administration summarized ocean temperature conditions for August in this description of the video above:
Clearly the current El Niņo warming in the tropical Pacific Ocean has contributed to the warm sea conditions. (UPDATE, 9/17: I've asked N.O.A.A. officials about their choice of temperature data sets, which has been criticized by some.) Variations in polar sea ice on short time scales, up or down, are essentially meaningless, my contacts studying the cryosphere always stress. Keep track of the long-term trends at the links above.