Climate change could cause sea ice growth

Sea ice in Antarctica is growing in some regions and shrinking in others. Photo / Getty Images

A new report helps explain why sea ice in Antarctica is growing as the ocean and air around it warm.

On Tuesday, Australia's Antarctic Climate and Ecocystems Cooperative Research Centre (ACE CRC) released a "position analysis" spanning nearly thirty years of research.

Sea ice is a "canary in the coal mine for climate scientists", the report's lead author Dr Jan Lieser told journalists, as it is particularly sensitive to changes in temperature, wind, ocean currents and solar radiation.

Yet, particularly in Antarctica, it is also difficult to understand. Sea ice goes through a rapid transformation every year - in Antarctica, from about three million square kilometres in summer to about 19 million square kilometres in winter.

As summarised in the ACE CRC report, sea ice in Antarctica has grown by about 1.5 per cent or 285,000 square kilometres per decade since 1979, as measured by its winter maximum. This compares to a loss of 3.5-4.1 per cent per decade in the Arctic.

This two trends are not necessarily inconsistent. At regional level, as the ACE CRC report points out, Antarctica is experiencing both sea ice growth near the Ross Sea and dramatic sea ice loss near the Bellingshausen Sea.

Speaking at the same briefing on Tuesday, the University of Melbourne's Professor Ian Simmonds said this could in part be explained by an increase in strong wind shifting ice around a region that is still extremely cold. "It's like an ice factory further south," he pointed out.

Increased wind intensity in the Southern Ocean has been linked to changes in atmospheric pressure, which have in turn been linked to ozone depletion and increased greenhouse gas concentrations.

Other factors - snowfall, sea ice thickness, melting freshwater ice and the "ridges" created by wind - also play a role in sea ice formation.

Simmonds stressed that action to reduce further climate change is needed. "We're seeing warming down to two kilometres in the Southern Ocean now - we don't see that in any other ocean," he said.

The ACE CRC report recommends further research including to get reliable estimates of sea ice volume in Antarctica.

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