Strong winds behind massive Antarctic ice shelves breaking off

Melbourne

Strong winds are causing vast Antarctic ice shelves to break off, such as the trillion-tonne iceberg that recently snapped away from the South Pole, scientists say.

The research showed how strengthening winds on the opposite side of Antarctica, up to 6,000 kilometres away, drive the high rate of ice melt along the West Antarctic Peninsula.

Researchers at the Centre of Excellence for Climate System Science in Australia found that the winds in East Antarctica can generate sea-level disturbances that propagate around the continent at almost 700 kilometres (km) per hour through a type of ocean wave known as a Kelvin wave.

When these waves encounter the steep underwater topography off the West Antarctic Peninsula they push warmer water towards the large ice shelves along the shoreline.

The warm Antarctic Circumpolar Current passes quite close to the continental shelf in this region, providing a source for this warm water.

"It is this combination of available warm water offshore, and a transport of this warm water onto the shelf, that has seen rapid ice shelf melt along the West Antarctic sector over the past several decades," said Paul Spence, from ARC Centre of Excellence for Climate System.

The changes in the Antarctic coastal winds, particularly along East Antarctica, might themselves be related to climate change, researchers said.

This is because as Earth warms the strong westerly winds associated with storms over the Southern Ocean contract toward the poles, in turn changing the winds near the Antarctic continent, they said.

When the researchers modelled the impacts of these altered winds on Antarctica they found that they could drive warming of up to one degree Celsius of the waters at the depth of floating ice shelves along the Western Antarctica Peninsula.

This could have significant implications for Antarctica's ice shelves and ice sheets, with previous research showing that even small increases in ocean temperatures can substantially increase melt rates around the Peninsula, researchers said.

"If we do take rapid action to counter global warming and slow the rise in temperatures, southern storms tracks are likely to return to a more northerly position," Spence said.

"That may slow the melting in Western Antarctica and bring more reliable autumn and winter rains back to the southern parts of Australia," he said.

"It would also limit ocean warming and give some of the world's major marine-terminating ice sheets a chance to stabilise," he added.

“It's vital we achieve this or we are likely to see more calving of large ice shelves, similar to the recent Larsen C event," Spence said.

A trillion-tonne iceberg — one of the largest ever recorded — broke away from Antarctica earlier this month and is now considered a serious hazard to ships around the South Pole.

The study was published in the journal Nature Climate Change. PTI