Frozen seas part to allow explorers a glimpse of dying glacier’s secrets

An Australian expedition last year has confirmed the Totten Glacier is being eroded from below by warm water.

An Australian expedition has revealed warm water is eroding the massive Totten Glacier in the Antarctic from below. Picture: Esmee van Wijk

A fateful parting of the frozen seas has given Australian ­researchers a unique understanding of the forces driving the rapid melting of Antarctica’s largest glacier.

Results of an expedition last year have confirmed the Totten Glacier is being eroded from below by warm water running through a wide channel.

The findings, presented in a new paper in Science Advances today sheds more light on one of the biggest unknown factors for global sea level rise projections.

The Totten Glacier is the largest in East Antarctica, and it contains enough ice to raise global sea levels by about 3.5 metres if it all melted.

In 2014-15, researchers aboard the Australian research vessel Aurora Australis were able to gather the first oceanographic data from the calving front of the Totten, when a long crack opened up in sea ice that is normally impenetrable to ships.

“The heavy sea ice conditions that had prevented previous ­expeditions from reaching the ice front relaxed briefly during a period of southwest winds, ­allowing access through a narrow and short-lived shore lead,” the paper said.

“Temperature, salinity, and oxygen were measured from the sea surface to within 8m of the sea floor at 10 stations along the calving front and fast ice edge.”

The lucky timing came about because of favourable winds but it involved some risk for the scientists involved if the ice pack had closed back up before measurements had been taken.

Lead author Steve Rintoul, interim director of CSIRO’s Climate Science Centre, said expedition members had “spent quite a long time debating whether to go or not”.

“We figured we had a 48-hour window and in that time we could do what we needed to and get out,” Dr Rintoul said.

Until now no oceanographic measurements from the Totten Ice Shelf have been available to test the hypothesis that warm ocean waters were driving melting of the ice shelf from below.

“We knew from satellite data that the Totten has been thinning faster than other glaciers in East Antarctica, but we didn’t know why,” Dr Rintoul said.

“A lucky break in the sea ice allowed us to get the ship in there and take the first measurements of the water column and sea floor in this area.

“We discovered a large channel in front of the western side of the Totten Glacier which is around 10km wide and up to a kilometre deep. We found that warm ocean water is reaching the ice shelf through this channel, with temperatures high enough to drive rapid melt of the underside of the ice shelf.

Dr Rintoul said scientists used to think it would take thousands of years for melting glaciers to dramatically impact sea levels.

But a recent study said melting ice could contribute an ­additional one metre to sea ­levels by 2100.