The collapse of ice sheets in West Antarctica is not inevitable, according to a study published in the journal Nature Communications. An international team of researchers, including from the University of Cambridge and Edinburgh, showed how the rate of ice meltdown varies significantly from region to region.
The team combined satellite images and ocean records to obtain the most detailed picture of how the West Antarctic Ice Sheet — which would raise global sea levels by 3.3 meters if it melted completely — is reacting to climate change.
The results show that the rate of ice meltdown along the coast varies significantly depending on regional climates. The good news is that, although the West Antarctic Ice Sheet continues to retreat, the extent of this meltdown is slowing down across a vulnerable area identified between 2003 and 2015. This slowdown was caused by changes in the surrounding water temperature, which in turn changed wind conditions.
Since the early 1990s, researchers have noticed faster ice melting in the marine-based West Antarctic Ice Sheet (home to the Pine Island and Thwaites glaciers), which has been attributed to human-induced climate change over the past century. Until now, researchers believed that once melting started, it could not be stopped, independently of any further climatic influence. It turns out that’s not necessarily the case.
“The idea that once a marine-based ice sheet passes a certain tipping point, it will cause a runaway response has been widely reported,” said Dr. Frazer Christie from Cambridge’s Scott Polar Research Institute, the paper’s lead author. “Despite this, questions remain about the extent to which ongoing changes in climate still regulate ice losses along the entire West Antarctic coastline.”
Using satellite images, the team found significant regional variations in how the West Antarctic Ice Sheet changed since 2003, with the extent of ice meltdown in the Amundsen Sea Sector much slower compared to the neighbouring Bellingshausen Sea Sector.
The researchers then compared climate and water records observed in these regions and linked them with changes in the strength and direction of surface winds. In this part of Antarctica, typically, the prevailing westerly winds stir up warmer, saltier water from deep in the ocean, which reaches the Antarctic coastline and increases the rate of ice melt.
However, this pattern changed between 2003 and 2015. “Between 2003 and 2015 offshore of the Amundsen Sea Sector, the intensity of the prevailing westerly winds reduced,” said Christie. “This meant that the deeper, warmer water couldn’t intrude, and we saw a notable change in corresponding glacier behaviour along the region: a clear reduction in the rate of melt and ice-mass loss.”
This study highlights the complex interactions between the ice sheets, ocean, and atmosphere and raises important questions about how quickly the icy continent will evolve in a warming world.
“Ocean and atmospheric forcing mechanisms still really, really matter in West Antarctica,” said co-author Professor Eric Steig from the University of Washington in Seattle. “That means that ice-sheet collapse is not inevitable. It depends on how climate changes over the next few decades, which we could influence in a positive way by reducing greenhouse gas emissions.”
Further work is needed to assess how important these mechanisms will be in the future as more and more ice continues to melt. “This study reinforces the urgent requirement to clarify how rapidly the most vulnerable regions of the West Antarctic Ice Sheet, such as Thwaites Glacier, will retreat, with global consequences for sea level rise,” said Bingham. “New data that we are currently acquiring from a traverse across Thwaites Glacier this January will directly address this goal.”
“There is an intimate link between the climate and how the ice is behaving,” concluded Christie. “We have the ability to mitigate West Antarctic ice losses – if we curb carbon emissions.”
Christie, F.D.W., Steig, E.J., Gourmelen, N. et al. Inter-decadal climate variability induces differential ice response along Pacific-facing West Antarctica. Nat Commun 14, 93 (2023). https://doi.org/10.1038/s41467-022-35471-3