The team’s research on the Totten Glacier has shown changing wind speeds over the Southern Ocean drive an upwelling of warmer ocean waters off the Antarctic coast.
This warmer water then penetrates beneath the floating part of the glacier (the ‘ice shelf’), causing the underside of the ice to melt and accelerate the flow of the glacier into the ocean.
Dr David Gwyther from the Institute for Marine and Antarctic Studies at the University of Tasmania, and a contributor to the new research, said the study combined satellite images of the ice sheet, wind stress data, and oceanography observations, to determine the chain of events that bring warm water to the Totten.
“Computer modelling shows that the atmosphere influences melting below East Antarctic ice shelves and affects the stability of the ice sheet,” Dr Gwyther said.
“Our new research provides strong evidence of the mechanistic links of heat transfer from the atmosphere, via the ocean, all the way to the ice sheet.
“This study also suggests that as wind speeds over the Southern Ocean are projected to increase with climate change, the Totten Glacier will melt faster and contribute more to global sea level rise.”
As the largest glacier in East Antarctica, the Totten Glacier has the potential to be a significant contributor to sea level rise. It drains 538 000 square kilometres of East Antarctica and discharges about 70 billion tonnes of ice each year.
Glaciologist Dr Jason Roberts, of the Australian Antarctic Division and Antarctic Climate and Ecosystems Cooperative Research Centre (ACE CRC), said the new research explains variations in the presence of warm water beneath the glacier reported in previous studies (Australian Antarctic Magazine 28: 12, 2015)
“Periods of stronger wind push surface water aside, allowing deeper and warmer water to rise up — or upwell — and replace it,” Dr Roberts said.
“This water can then flow into the shallower and colder seas of the continental shelf around Antarctica. In places such as the Totten Glacier, canyons in the sea floor allow this relatively warm water to penetrate deep under the floating ice and increase melting.
“The wind-driven upwelling explains why these submarine canyons get flushed with warm water in some years and cold water in others, and the subsequent variability in the melting of the Totten Glacier.”
This summer, Australian Antarctic Division scientists recovered instruments deployed on the Totten Glacier in 2016–17, to measure changes in ice thickness and flow, and ocean-driven melting from below (see next story). The data will further refine understanding of the fundamental processes involved in ice shelf thinning.
The study, published in Science Advances, was led by Chad Greene of the University of Texas. Australia’s contribution was funded through the Australian Research Council Antarctic Gateway Partnership and Australian Antarctic Division.
Australian Antarctic Division