Bob CollinsNASA has a whole lot of “who knows” in its release today about sea ice around Antarctica.
It released a series of images today, showing winter and summer sea ice around the continent, none of which appears to show a trend one way or the other.
Since the start of the satellite record, total Antarctic sea ice has increased by about 1 percent per decade. Whether the small overall increase in sea ice extent is a sign of meaningful change in the Antarctic is uncertain because ice extents in the Southern Hemisphere vary considerably from year to year and from place to place around the continent. Considered individually, only the Ross Sea sector had a significant positive trend, while sea ice extent has actually decreased in the Bellingshausen and Amundsen Seas. In short, Antarctic sea ice shows a small positive trend, but large scale variations make the trend very noisy.
The year-to-year and place-to-place variability is evident in the past decade. The winter maximum in the Weddell Sea, for example, is above the median in some years and below it others. In any given year, sea ice concentration may be below the median in one sector, but above the median in another; in September 2000, for example, ice concentrations in the Ross Sea were above the median extent, while those in the Pacific were below it.
NASA’s cautious assessment contrasts with assertions last week that the ice shelf near the Pine Island Glacier in West Antactica is melting at an increasing rate, and could raise sea levels by 25 centimeters — almost 10 inches.
By the way, it’s the dead of winter in Antarctica now. The temperature at the moment in Vostok is -89 °F. There’ll be no melting there today.
