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Stronger winds heat up West Antarctic ice melt

Strengthening winds in the East Antarctic generate Kelvin waves that lead to increasing melting along the West Antarctic Peninsula.

Date:

July 17, 2017

Source:

University of New South Wales

Summary:

Stronger winds 6000kms away on the East Antarctic, have generated waves that circle the continent at almost 700kmh. When these waves meet the steep underwater topography of the West Antarctic Peninsula they push warm water under the ice shelves. This helps explain the increased ice melt in this region that can lead trillion tonne ice shelves, like Larsen C, to break away from the continent.

New research published in Nature Climate Change has revealed how strengthening winds on the opposite side of Antarctica, up to 6000kms away, drive the high rate of ice melt along the West Antarctic Peninsula.

Researchers from the ARC Centre of Excellence for Climate System Science found that the winds in East Antarctica can generate sea-level disturbances that propagate around the continent at almost 700 kilometers per hour via 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 lead researcher Dr Paul Spence.

"We always knew warm water was finding its way into this area but the precise mechanism has remained unclear. That remote winds on the opposite side of Antarctica can cause such a substantial subsurface warming is a worrying aspect of the circulation at the Antarctic margin."

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

When the researchers modeled the impacts of these altered winds on Antarctica they found that they could drive warming of up to 1°C 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.

"For lack of precise estimates of future change, scientists have remained conservative in what this melting means for the globe, but recent estimates suggest Antarctica could contribute more than a metre to sea-level rise by 2100 and over 15 metres by 2500 under current emissions trajectories," Dr Spence said.

"This would be disastrous for coastal regions and displace hundreds of millions of people worldwide."

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

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

Story Source:

Materials provided by University of New South Wales. Note: Content may be edited for style and length.

Journal Reference:

Paul Spence, Ryan M. Holmes, Andrew McC. Hogg, Stephen M. Griffies, Kial D. Stewart, Matthew H. England. Localized rapid warming of West Antarctic subsurface waters by remote winds. Nature Climate Change, 2017; DOI: 10.1038/nclimate3335