The Thwaites Glacier is Moving as Fast as It Can, and Why It Could Prevent Sea Level Rise by Hundreds of Meters (or More)
According to co-author Peter Davis, the work doesn’t bring any good news in terms of sea-level rise. The glacier is moving as quickly as it can.
The Thwaites Glacier is roughly the size of Florida and is located in West Antarctica. Part of what holds it in place is an ice shelf that juts out onto the surface of the ocean. The shelf acts like a cork, holding the glacier back on the land and providing an important defense against sea level rise.
The researchers found that melt rates on the underside of the ice were just 2–5.4 metres per year, much lower than the 14–32 metres predicted by models1. “That was very surprising,” says Davis.
About 4% of the sea level rise every year is contributed by the ice melting into the ocean. Particularly rapid melting happens at the point where the glacier meets the seafloor, which has retreated nearly nine miles (14 kilometers) since the late 1990s, exposing a larger slice of ice to relatively warm ocean water.
The complete collapse of the Thwaites itself could lead to sea level rise of more than two feet (70 centimeters), which would be enough to devastate coastal communities around the world. The sea level could rise as much as ten feet if the Thwaites collapse, as it is acting like a natural dam to the surrounding ice.
While it could take hundreds or thousands of years, the ice shelf could disintegrate much sooner, triggering a retreat of the glacier which is both unstable and potentially irreversible.
Making Sense of the Doomsday Glacier: A Torpedo-like Robot to Follow the Melting Glaciers in Antarctica
They sent instruments down and bored a hole into the ice using a hot water drill, which allowed them to get more information from the glacier.
The instruments included a torpedo-like robot called Icefin, which allowed them access to areas previously almost impossible to survey. The vehicle took pictures and recorded information about the ocean currents and the temperature of the water.
Britney Schmidt, associate professor at Cornell University and a lead author on one of the papers, said the data was collected from the sea floor all the way to the ice.
The results of the research reveal “a very nuanced and complex picture,” Peter Davis, an oceanographer at the British Antarctic Survey and a lead author on the other paper, told CNN.
“The glacier is still in trouble,” Davis said in a statement, adding, “What we have found is that despite small amounts of melting there is still rapid glacier retreat, so it seems that it doesn’t take a lot to push the glacier out of balance.”
The research team found that the area’s melting was very rapid. Warm, salty water was able to funnel through and widen cracks and crevasses, contributing to instabilities in the glacier.
We were aware of the glaciers changing. We were aware that it was related to ocean temperature. We were aware that the ground was melting. We knew that the atmosphere was warming. We were aware that the glaciers were collapsing.
Davis said that research can help make more accurate forecasts of sea level rise, which can be used to mitigate climate change and protect coastal communities. From a more personal perspective, he said, he also hopes it prompts people “to sit up and take notice of the changes that are occurring.”
Icefin the robot is designed to go where no human can, swimming off the coast of Antarctica under 2,000 feet of ice. Lowered through a hole with water, the machine takes readings and takes video of the glacier. This Florida-sized chunk of ice is also known as the Doomsday Glacier, and for good reason: It’s rapidly deteriorating, and if it collapses, global sea levels could rise over a foot. It would add 10 feet to rising seas if it were to tug on surrounding glaciers.
They might be sending shocks through the system when features melt. Thwaites is falling apart and we know about it. For the last 30 years we’ve been watching rifts and crevasses spread across the system and destabilizing the ice shelf. And what we’re showing here is the way that the ocean kind of works into these weak spots, and in a sense makes it worse.”
The Intergovernmental Panel on Climate Change predicts that sea levels will probably rise by between 38 and 77 centimetres by 2100, but the collapse or melting of ice sheets in Greenland and the Antarctic could theoretically contribute an additional metre. Britney Schmidt, an Earth scientist at Cornell University in Ithaca, New York, who is a co-author of both papers, says all of this is to beat down those uncertainties.
Researchers think that grounding-line retreat is driven by warm ocean water melting the underside of the ice. Warming temperatures due to climate change allow a patch of warm water to flow towards the West Antarctic.
The water was a bit above the freezing point. The ice had a thin layer of cold fresh melt water on the underside and this made it hard to transfer heat to the ice. You should get the heat through the protective layer, as there’s more than enough to drive really rapid melting.
“These types of hard-fought observations are absolutely critical to refining the treatment of these processes in the models we use to predict the ice sheet’s future,” says Robert DeConto, a geophysicist and ice modeller at the University of Massachusetts Amherst. “We need more of them.”
When this information gets into models, it should be more accurate predictions of how sea levels will change. It’s unclear whether this will paint a more frightening picture or a more reassuring one. “I really didn’t have the authority to speculate,” says Schmidt.