A new study of the rate at which Antarctica’s Totten Glacier ice shelf is melting has highlighted the difficulty of distinguishing between ice-loss caused by climate change and melting driven by natural ocean processes. 

(Image: Totten ice front. Credit: Esmee van Wijk)

Totten Glacier is the largest glacier in East Antarctica and has the potential to make a significant contribution to global sea level rise.

Between 2003 and 2008 the base of the glacier’s ice shelf was observed to be thinning at a rate of about 40 centimetres per annum.

However, recent research looking at data over a longer, 18-year timescale identified large, periodic 3-4 year fluctuations but no net change in the ice shelf’s thickness.

IMAS researcher Dr David Gwyther, lead author of a paper published in the journal Nature Communications, said his research team’s ocean model simulations showed that a large fraction of the fluctuation in melting at the base of the Totten Glacier could be explained by variability in natural ocean processes.

“Totten Glacier has the potential to have a major impact on global sea levels so it’s important that we understand how and why the ice shelf is changing and what might happen in the future,” Dr Gwyther said.

“To do that, we need to be able to distinguish between the impact of climate change and natural variability resulting from processes internal to the ocean, such as vortex-like eddies.

“Our modelling has shown that making this distinction is not a simple process.

“We found that intrinsic (natural) ocean processes accounted for 44 per cent of the variability in melting under the ice shelf over one to five years, and 21 per cent of the variability over a five to ten year period.

“Climate change accounted for variability of around the same magnitude.

“This complex variability in the processes causing melting of the Totten ice shelf limits the conclusions that we can reach from short-term observations, as we are likely also monitoring natural variability, rather than solely climate change.

“Our study suggests that to fully understand and predict the behaviour of the glacier, we need to combine short term observations with data collected over a longer period and use modelling studies which can explore the long-term trends,” Dr Gwyther said.

The research was supported by the Australian Research Council funded Antarctic Gateway Partnership and also included scientists from CSIRO, the Australian Antarctic DivisionACE CRC and the Institute for Geophysics at the University of Texas.

Authorised by the Executive Director, Institute for Marine and Antarctic Studies
August 22, 2018