For the second year in a row the Antarctic has set a new record for sea ice extent.
Daily Antarctic sea ice extent as plotted by the University of Bremen using satellite data. 2014 is the red line. Courtesy: University of Bremen.
Satellite data suggests that Antarctic sea ice extent – the extent of ocean that is covered by sea ice over at least 15 per cent of its area – was some 19.62 million square kilometers on 12 September 2014. This 1.12 million square kilometers above the long term average over the period from 1981 to 2010.
Data compiled by the Center for Australian Weather and Climate Research shows that this daily sea ice extent measurement is both the highest recorded for day 255 in the annual calendar and an all time record high for the Antarctic during the period that satellite measurements have been kept (since 1978).
The causes of this significant and continuing growth in the extent of Antarctic sea ice remains a mystery – as the Intergovernmental Panel on Climate Change (IPCC) implicitly acknowledged in its report last year – although there have been a number of possible explanations discussed in the scientific literature.
Research from a team led by Xichen Li of New York University and published in Nature earlier this year suggested that the gradual warming of the North and tropical Atlantic Ocean is affecting Antarctica. Specifically, the research stated that warming of Atlantic waters was followed by changes in sea-level pressure in the Antarctic’s Amundsen Sea. In addition, these warming patterns also preceded redistribution of sea ice between the Antarctic’s Ross and Amundsen-Bellingshausen-Weddell Seas.
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 used computer models to study the interaction between wind and ice and concluded 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.