Bottom-up melting biggest driver of Antarctic ice shelf loss, says study

• June 20, 2013
Antarctic ice shelf loss

Ocean warming could be the biggest contributor to ice shelf melt in Antarctica, warns a new study. Creative Commons: Liam Quinn, 2011

Bottom-up ice shelf melt, caused by warming oceans, could be the biggest contributor to ice shelf loss in Antarctica, according to a new study looking to shed light on the world’s most mysterious ice sheet.

There is huge scientific interest in understanding and monitoring how the world’s ice sheets are changing. As the ice on land melts it drains into the sea, causing sea levels to rise.

There are several different ways the Antarctic ice sheet is shrinking – from the icy surface to the ocean below – and understanding these processes could be key to knowing how fast this melting ice sheet is raising sea levels.

To understand how most of the ice is lost from Antarctica, a new study just published in the journal Science looks to the ice shelves that surround 75 per cent of the continent.

Ice shelves are floating extensions of land ice that act as buttresses, stopping ice flowing from the interior straight out into the ocean.

Traditionally, scientists thought large chunks of solid ice breaking off the ice shelves was the main source of ice loss from Antarctica – a process known as iceberg calving.

But there’s another way. As the ocean below the ice shelves warms, the ice melts from the bottom up – something scientists call basal melting. With melting from the top and bottom, some ice shelves are getting noticeably thinner, says the new study.

The paper looked at both processes of ice loss across 99.5 per cent of Antarctica’s ice shelves between 2003 and 2008. Overall, the scientists found basal melting caused 55 per cent of ice loss, although they saw quite a lot of variation between regions.

This makes bottom-up ice shelf melt the largest source of ice shelf loss in Antarctica, the paper suggests. Previous studies have estimated the contribution to be more like 30 per cent, or even as low as 10 per cent.

Read more: Carbon Brief >>


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