Dramatic loss of Arctic sea ice, in stark contrast to the Antarctic, says UC lecturer

The Arctic has suffered a staggering loss in sea ice, in stark contrast to the Antarctic, a University of Canterbury (UC) lecturer said today.

This last northern season the Arctic experienced a record minimum in sea extent, and with this trend continuing the sea ice in the Arctic is expected to disappear over summer in the near future, with uncertain consequences for the global climate, UC senior lecturer Wolfgang Rack said today.

``Sea ice shrinkage in the North is in stark contrast to the Antarctic, where a slight overall increase in sea ice coverage is observed. However, there are significant regional differences. A significant increase in the Ross Sea is almost balanced by a significant decrease in the Amundsen - Bellingshausen Sea.

``A recent publication suggests that there was slight overall decrease in thickness in the Ross Sea. Our study suggests there was a significant increase in multiyear sea ice thickness in McMurdo Sound over the period 2003-2009, which is likely related to the close inter-action of sea ice and ice shelf in this area.

``The stark contrast between the Arctic and Antarctic might be partly explained by the slight cooling trend observed in many parts of the Antarctic, which is believed to be a consequence of the Ozone hole.

``However, the sea ice in the Southern Ocean is dynamic from year to year and in between seasons, and it needs a much better understanding of the interaction between sea ice and the atmosphere ocean system to come up with reliable predictions,'' Dr Rack said.

In the Antarctic where the ocean was warming and sea ice was reduced scientists were also observing retreating land ice, like at the West Antarctic Ice Sheet. It was not completely clear how this was linked, but if this process continued then sea levels were expected to rise higher, he said.

UC's Gateway Antarctica has employed a post-doctoral researcher in atmospheric modelling who should strengthen this research at UC contributing to a better understanding of this important part of the climate system.

There are no ice shelves in Greenland, because it is too warm, whereas 75 percent of the Antarctic coastline is bordered by ice shelves. Reduction of the grounded ice sheet contributes to sea level rise, which is not the case for ice shelf, which is already floating in water. However, reduction of ice shelves speeds up the loss of grounded ice.

``It makes a huge difference for climate if the southern ocean is covered by ice or not. New Zealand is surrounded by the southern ocean; our climate is going to change. Water levels will raise if the ice sheets melts. We need to know how fast the changes will occur. How much sea level rise in the next 100 years?'' he said.

Dr Rack will deliver an address as part of Icefest at the UC Science Cafe on Saturday.