Two studies this week shed new light on the melting of Thwaites Glacier, one of Antarctica’s largest and most threatening ice expanses. Often called the “end of the world glacier,” this glacier alone contains enough ice to raise the world’s sea levels by about two feet.
A new study contains some sobering conclusions. On the one hand, Thwaites may be melting more slowly than previous estimates suggested. On the other hand, there is a rapid retreat from the sea to the inland. This suggests that it may take less time to destabilize glaciers than scientists once thought.
“Our results are astonishing, but glaciers are still in trouble,” said lead author of the study, oceanographer Peter Davis, in a statement. “What we have found is that despite the small amount of melting, there is still rapid glacier retreat, so it doesn’t seem like it will take long to unbalance the glacier.”
Two studies published Wednesday in the journal Nature, reports some of the most recent findings from the International Thwaites Glacier Collaboration, a joint initiative of the US National Science Foundation and the UK’s National Environmental Research Council. Launched in 2018, the project explores the factors that drive the melting and retreat of large glaciers.
The two studies specifically report findings from an initiative known as the MELT project, an effort to understand how warm ocean waters are driving melting at the grounding lines of glaciers. It is the point at which the ice attaches to the bedrock and anchors it to the earth. Beyond the ground line, the ice leaves the ground and protrudes in front of the glacier in the form of a floating ice shelf.
These are a very important part of seaside glaciers. Sea water can seep under the ice shelf and hit the edge of the glacier at the ground line, melting the ice from below. This process can push glaciers back over the bedrock and retreat inland, pouring more ice into the ocean in the process.
In a worst-case scenario, sufficient melting could thin the ice shelf itself and eventually cause it to collapse. This can destabilize the ice wall behind the ledge and cause the glacier to retreat rapidly.
Thwaites contains so much ice that it has so much potential to affect the world’s sea levels that scientists are obsessed with understanding the processes by which the ice melts and retreats.
Two studies published this week use a variety of methods to investigate the melting occurring in Thwaites ground wires. One research group drilled a hole in the ice and installed a mooring with a special sensor just downstream of the ground wire. Another group used an autonomous underwater vehicle known as Icefin to collect observations.
Both studies yielded surprising findings. Much of the melting under ice is occurring more slowly than previous estimates suggested. Water temperatures in this area are generally well above freezing, but the currents are slow and the water is highly stratified. It consists of overlapping layers of warm and cold water that do not mix easily. These conditions make it difficult for the warmest water to melt ice.
The findings show that Thwaites is retreating and melting less than previous studies suggested. This means it may be more sensitive to small levels of melting than scientists previously thought.
But Icefin’s research reveals a second surprise. Melting rates are generally slower than expected under the ice shelf, but in some areas there are sudden spikes in melting rates.
Icefin found that under the ledge there are certain areas where the smoothness of the ice is reduced and filled with crevasses and steep terraces. In some of these rough sections of ice, the melting rate was found to be six times higher than the average melting rate observed by the instrument in the smoother regions.
Cornell University oceanographer Britney Schmidt, lead author of the study, said these high-melt areas could help “wear away the weakest parts of the glacier.” This means that it could be driving the retreat of glaciers.
In comments to the new study published Wednesday, Nature, Ice expert Craig McConnochie warns that the study focuses on “a small fraction of a single glacier.” Other Antarctic glaciers have unique characteristics, and similar studies need to be conducted to pinpoint the factors driving their melting and retreat, he added.
Taken together, though, these studies suggest that there may be a lot more going on beneath Thwaites’ icy surface than scientists previously understood.
“These new ways of looking at glaciers allow us to understand not just how much melting is happening, but how and where it is happening, which is important in the very warm regions of Antarctica.” said Schmitt.
Reprinted from E&E News with permission of POLITICO, LLC. Copyright 2023. E&E News provides essential news for energy and environmental professionals.
