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A Twenty-Year Record of Changes in Antarctic Sea Ice
Reference
Zwally, H.J., Comiso, J.C., Parkinson, C.L. Cavalieri, D.J. and Gloersen, P. 2002. Variability of Antarctic sea ice 1979-1998. Journal of Geophysical Research 107: 10.1029/2000JC000733.

What was done
For the 20-year period 1979-1998, the authors examined passive microwave observations from several satellites to analyze trends in Antarctic sea ice extent (defined as the total area of all 25- x 25-km grid cells having at least 15% sea ice concentration) and sea ice area (defined as the total area of the ocean actually covered by sea ice).

What was learned
For the entire Southern Ocean, sea ice extent was found to have increased by 11,181 4190 square km per year, or by 0.98 0.37 percent per decade. Sea ice area for the Southern Ocean was also shown to have increased by nearly the same amount: 10,860 3720 square km per year, or 1.26 0.43 percent per decade. Regionally, trends in sea ice extent were positive in the Weddell Sea, the Pacific Ocean and the Ross Sea; while they were nearly in balance to slightly negative in the Indian Ocean, and negative in the Bellingshausen/Amundsen Seas. In terms of variability, the interannual variability of the mean sea ice extent was only 1.6%; while monthly variability in sea ice extent was 4.0% over the first ten years of the record, declining to 2.7% over the last ten years.

The authors also derived a relationship describing the linkage between regional sea ice extent and spatially-averaged surface temperature over the ice pack. This relationship indicated that a one-degree-Celsius drop in air temperature would increase sea ice extent by approximately 0.7%.

What it means
The observed increase in Antarctic sea ice area and extent over the past twenty years is consistent with the concomitant temperature decrease observed over earth's vast southern continent (see Antarctica - Temperature in our Subject Index); but it stands in stark contrast to climate-alarmist predictions of widespread melting of the planet's polar ice caps as a consequence of CO2-induced global warming. For that matter, it stands in stark contrast to predictions of CO2-induced global warming period.


Reviewed 2 October 2002