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Sea ice extent in the Antarctic reached a record level in June with an anomaly of some 2.074 million square kilometers above the long term average, according to data published by the University of Illinois Polar Research Group (see top right).
This is statistically significant as the latest data published by the US National Snow and Ice Data Center (NSIDC) shows that sea ice extent in June is more than two standard deviations above the long term average for the period from 1981 to 2010, and has been since April (see bottom right).
The extent of sea ice around the Antarctic has been growing steadily at a rate of around 2.6 per cent per decade, according to NSIDC data. This contrasts with the long term decline in Arctic sea ice. The mystery of increasing Antarctic sea ice during an era of record high global surface temperatures has puzzled climate scientists.
There are some suggestions from computer model research and evidence from satellite tracking of ice that Antarctic sea ice growth in recent years may be due to wind intensification and ocean circulation changes.
A paper published in Nature Geoscience by Paul Holland of the British Antarctic Survey and Ron Kwok of the Jet Propulsion Laboratory of the California Institute of Technology presented satellite tracking evidence that “reveals large and statistically significant trends in Antarctic ice drift, which, in most sectors, can be linked to local winds”. Jinlun Zhang of the University of Washington has used computer models to study the interaction between wind and ice and in a recent paper he concludes that changes in winds are resulting in both more compaction within the ice pack and more ridging, causing a thickening of the pack and making it more resistant to summer melt. In simple terms, wind drives ice out to sea, creating open water near the ice-edge that is more likely to freeze.
But this explanation is far from proven and it is clear that climate scientists can not completely explain what is happening in the Antarctic as the IPCC admitted recently in its latest scientific report published in September when it stated that there is “low confidence in the scientific understanding of the observed increase in Antarctic sea ice extent since 1979”. The IPCC explained that “the shortness of the observed record and differences in simulated and observed variability preclude an assessment of whether or not the observed increase since 1979 is inconsistent with internal variability”.
Note added 2 July 2014:
The commentary to the release of June satellite temperature measurements of global tropospheric temperatures from University of Alabama in Huntsville (UAH) released on 1 July 2014 states: "Compared to seasonal norms, the coldest place in Earth's atmosphere in June was over the Ross Ice Shelf, where Antarctic winter temperatures were as much as 5.37 C (about 9.67 degrees Fahrenheit) colder than seasonal norms."
This story updated with UAH comment at 1230 2 July 2014.
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