Researchers in Antarctica report a concerning new discovery that had not been anticipated in their existing models involving ice melting on Earth’s southernmost continent.
According to new findings, relatively warm water that can make its way beneath Antarctica’s ice sheets can cause additional melting from below that had not been previously known to scientists.
The new research, undertaken by scientists with the British Antarctic Survey (BAS), reveals the problems posed by warm seawater. This water seeps into the lower portions of ground-based ice, thereby accelerating not only ice melt but also its movement into the surrounding ocean.
Additionally, the results could help climate researchers develop a clearer picture of how Antarctic ice melt contributes to rising sea levels and other changes that could impact far-reaching areas around the world in the years ahead.
BAS researcher Alex Bradley, who specializes in ice dynamics and served as lead author of the new study, says his team has identified what they believe could be “a new tipping point in Antarctic ice sheet melting.”
“This means our projections of sea level rise might be significant underestimates,” Bradley recently warned in a statement.
Chilling Discoveries Within the Grounding Zone
Bradley and his team’s study focuses on the grounding zone, which describes an area beneath the Antarctic ice sheet where the ground-based ice on the continent meets the sea.
Land-based ice in Antarctica moves gradually over long periods, making its way into the ocean, where it begins to melt once it meets the seawater. However, over time, climate change has been accelerating both the movement of the ice sheets and warming the surrounding seawater. Such processes are identified as major contributors to sea level rise, which can affect coastlines all around the world.
“We reveal a sensitive dependence of the grounding-zone dynamics,” the team writes in their new paper, noting that “as the grounding zone widens in response to melting, both temperature and flow velocity in the region increase, further enhancing melting.”
“We find that increases in ocean temperature can lead to a tipping point being passed, beyond which ocean water intrudes in an unbounded manner beneath the ice sheet, via a process of runaway melting.”
“Additionally,” they add, “this tipping point may not be easily detected with early warning indicators.”
Seawater Working Its Way Beneath Antarctica
In the team’s new study, they modeled how seawater makes its way into the areas between the land and the ice sheet above, effectively lubricating the ice bed and quickening its movement toward the nearby ocean.
This process of speeding along the movement of Antarctica’s ice is further quickened by the presence of warmer seawater.
“Ice sheets are very sensitive to melting in their grounding zones,” Bradley recently said, adding that grounding zone melt he and his colleagues have observed “displays a ‘tipping point like’ behaviour, where a very small change in ocean temperature can cause a very big increase in grounding zone melting, which would lead to a very big change in flow of the ice above it.”
When warm water begins to seep into the grounding zone, cavities open up, allowing additional water into the area, precipitating the melt. Even a small increase in water temperature would likely significantly impact the amount of melting that occurs.
“Our results point towards a stronger sensitivity of ice-sheet melting,” Bradley and his co-author write in their recent study, emphasizing that such dynamics contribute to “higher sea-level-rise contribution in a warming climate” than scientists had previously been able to discern from past studies.
Absent from Existing Models
Given that such factors are currently absent from models scientists rely on to determine the amount of melt that can occur, it seems likely that warm seawater and its impact on ice within the grounding zone can account for some of the accelerated shrinkage of ice sheets observed by the Intergovernmental Panel on Climate Change (IPCC) and others. This would also relate to ice sheets in other parts of the world apart from Antarctica such as Greenland, where similar ice melt has been observed to occur at rates faster than scientists expected based on existing models.
Bradly called the new data “missing physics” that, while remaining absent from current models, prohibits scientists from accurately projecting the potential impact of ice melt in the Earth’s polar regions.
“They don’t have the ability to simulate melting beneath grounded ice, which we think is happening,” Bradley says, adding that he and his colleagues are “working on putting that into our models now.”
Bradley and his team’s findings were detailed in a new study, “Tipping point in ice-sheet grounding-zone melting due to ocean water intrusion,” co-authored with Ian J. Hewitt and published in the journal Nature Geoscience on June 25, 2024.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. He can be reached by email at micah@thedebrief.org. Follow his work at micahhanks.com and on X: @MicahHanks.