A robotic Argo float has completed an ocean transect beneath an East Antarctic ice shelf – said to be the first of its kind – after spending more than eight months under the Denman and Shackleton ice shelves and collecting detailed temperature and salinity data.
Over two-and-a-half years, the float completed a 300km drift, collecting nearly 200 profiles from previously unsampled parts of the ocean. The mission offers rare insights into how ocean conditions are influencing the stability of East Antarctica’s ice.
“We got lucky,” said Dr Steve Rintoul, oceanographer at SCIRO and partner with the Australian Antarctic Program Partnership. “Our intrepid float drifted beneath the ice and spent eight months under the Denman and Shackleton ice shelves, collecting profiles from the seafloor to the base of the ice every five days. These unprecedented observations provide new insights into the vulnerability of the ice shelves.”
The data shows that the Shackleton Ice Shelf – the most northerly in East Antarctica – is not currently exposed to warm water capable of driving basal melt. By contrast, warm water is reaching the base of the Denman Glacier, which has a potential 1.5m contribution to global sea-level rise. Small changes in the thickness of this warm water layer could significantly accelerate melt and trigger unstable retreat.
A key scientific gain comes from measurements within the 10m boundary layer directly beneath the ice, which strongly controls melt rates. “A great advantage of floats is that they can measure the properties of the boundary layer that control the melt rate,” Dr Rintoul explained. “The float measurements will be used to improve how these processes are represented in computer models, reducing the uncertainty in projections of future sea-level rise.”
He added that deploying additional floats along the Antarctic continental shelf “would transform our understanding of the vulnerability of ice shelves to changes in the ocean.”
Prof. Delphine Lannuzel, leader of the Australian Antarctic Program Partnership, called the achievement “an amazing story of the little float that could,” noting that “under incredibly testing conditions, a relatively tiny instrument has delivered us a wealth of invaluable information.”
The research is published in Science Advances and supported by CSIRO, the Australian Antarctic Program Partnership, IMAS and Australia’s Integrated Marine Observing System.
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