A Northumbria University researcher is part of a team that has produced the first physics-based quantifiable evidence that thinning ice shelves in Antarctica are causing more ice to flow from the land into the ocean. Their findings have been published in Geophysical Research Letters.
Satellite measurements taken between 1994 and 2017 have detected significant changes in the thickness of the floating ice shelves that surround the Antarctic Ice Sheet. These shelves buttress against the land-based ice, holding them in place like a safety band. While it has been suggested that the thinning ice shelves were responsible for a direct loss of ice from the land-based ice sheet into the ocean, there was no actual evidence linking data and physics that could demonstrate this, until now.
Researchers in the UK and US have now undertaken the first continent-wide assessment of the impact the thinning ice shelves are having on the flow of ice in Antarctica. They were particularly interested in seeing how much ice flowed across the ‘grounding line’. This is the point where the land-based ice sheet meets the sea-based ice shelves.
They used a state-of-the-art ice-flow model developed at Northumbria and newly available measurements of changes in the geometry of ice shelves to calculate the changes in grounded ice flow. When the modelled results were compared with those obtained by satellites over the last 25 years, the researchers found what they described as ‘striking and robust’ similarities in the pattern of ice flowing from the ice sheet into the ocean.
The largest impact was found in West Antarctica, which already makes a significant contribution to sea level change. The largest changes are taking place around the Pine Island and Thwaites glaciers. On Pine Island Glacier, evidence of these changes could be seen almost 100 miles (150km) inland, upstream of the grounding line.
A detailed view of changes in ice flow around the Pine Island and Thwaites glaciers on the Amundsen Sea, due to thinning sea-based ice shelves. Pine Island Glacier is at the top right of the image, with changes in ice seen almost 100 miles inland.
Hilmar Gudmundsson, Professor of Glaciology and Extreme Environments, led the study. He said there has been a long-standing question as to what was causing the changes we have observed in land-based ice over the last 25 years, and that while the thinning of the floating ice-shelves had been suggested as a reason, the idea had never been put to the test before now. “I found it striking how well our modelled changes agree with the pattern of observed mass loss,” he said. Read more.