Scientists worry that many glaciers will collapse by the end of the century due to rapid glacier melting brought on by global warming, which will cause sea levels to rise significantly and inundate coastal communities and island nations.
A scientist from the University of California, Berkeley has updated the glacial movement model, which may make it easier to identify the Arctic and Antarctic glaciers that are most likely to slide downhill and tumble into the ocean.
The effects of meltwater that seeps to a glacier’s base and facilitates its downhill flow are taken into account in the new model, which was published last week in the journal The Cryosphere. The thickest glaciers with a history of faster flow even if that rapid flow is periodic are predicted to be the most at risk by the new physical model.
“The model suggests that thick and fast-flowing glaciers are more sensitive to lubrication than thin and slow glaciers,” said Whyjay Zheng, a postdoctoral fellow in the UC Berkeley Department of Statistics. “The data from Greenland glaciers support this new finding, indicating that those fast and thick glacier beasts might be more unstable than we thought under global warming.”
With the effects of global warming, Zheng created a new model that included a mechanism that has gained more significance: meltwater seeping into glacier bottoms and facilitating glaciers’ descent over bedrock.
The Antarctic recorded record high temperatures of 70 degrees Fahrenheit above average in March, while certain areas of the Arctic were more than 60 degrees warmer than typical. The Arctic and Antarctic have warmed more than the rest of the planet. Many glaciers, especially those in Greenland, experience the formation of meltwater lakes as a result of the warmer weather.
Through a process known as hydrofracture, lakes can penetrate glaciers to reach their base, or they can drain into nearby crevasses. Glaciologists have already observed that the acceleration and slowing of glaciers are linked to the processes taking place at their fronts, where the ice merges with warmer ocean water.
This is the first time we saw such a gigantic collapse of an ice cap. Once it started to speed up, it maintained its speed for a long time. We think one of the most likely reasons is that it created a lot of crevasses on the surface, and those crevasses are pipelines for the surface meltwater to go down into the bottom of the glacier. Now, water comes down more easily and effectively reduces the friction, so the glacier can keep sliding fast, and even faster if the climate gets further warmed up.
Whyjay Zheng
According to observations, several of these marine-terminating glaciers tend to accelerate once their fronts calve into the water. The glaciers slow when the fronts approach the ocean. As a result, the main attention has been given to what is taking place at the glacier terminus.
However, it looks that basal lubrication by meltwater is causing a feedback loop that speeds up glaciers that have already accelerated for other reasons, such as changes at the terminus.
“In Greenland, the glacier’s speed seems to be mostly controlled by the terminus position: If the terminus is retreating, then the glacier will speed up; if the terminus is advancing, the glacier will slow down,” Zheng said. “People think this is probably the primary reason why the Greenland glaciers can speed up or slow down. But now, we are starting to think there’s another and maybe quicker way to make glaciers slow down or speed up basal lubrication.”
In order to incorporate meltwater lubrication into the popular perturbation model of glacier flow, Zheng set out to alter it using common fluid flow equations.
He compared the model’s projections to glaciers in Svalbard, a Norwegian archipelago, and Greenland, which is a part of Denmark. When compared to data of glacier flow during a 20-year period, from 1998 to 2018, the prediction that thicker, faster-moving glaciers are more likely to shrink and discharge into the ocean was made.
“Basal lubrication creates a positive feedback loop,” Zheng said. “The faster glaciers are more likely to respond faster to basal lubrication, and the following speedup makes them more prone to future lubrications. For example, if a glacier is flowing 3 kilometers per year, and basal lubrication suddenly happens, it will react so fast that you can see the fluctuation of the speed, probably just a few days later, compared to another glacier that would be flowing at 100 meters per year.”
The consequence is that thick, swift glaciers near the Arctic and Antarctic should be regularly observed, just as glaciers are already observed for changes at the terminus, to foresee the discharge of big icebergs into the ocean that may have an impact on sea level. Better methods of gauging basal lubrication are also required, according to Zheng.
“If the glacier has a potential to be disrupted in a short time and drain a lot of the ice into the ocean, perhaps within a year or two, that could be something we have to worry about,” he said.
Zheng studied an ice cap in the Siberian Arctic called the Vavilov Ice Cap on the Russian island of Severnaya Zemlya that suddenly collapsed over a period of several years, at one point in 2015 speeding up to 9 kilometers per year. This ice cap sparked Zheng’s interest in the basal lubrication of glaciers. Zheng has a background in geophysics, planetary science, and remote sensing.
As a result of basal lubrication and the advance of the terminus into the ocean, which reduced friction at the front of the glacier that was holding the glacier back, the immobile ice cap changed from a glacier that was moving slowly to one that was moving quickly after he examined the incident. About 11% of the ice cap flowed into the ocean between 2013 and 2019.
“This is the first time we saw such a gigantic collapse of an ice cap,” he said. “Once it started to speed up, it maintained its speed for a long time. We think one of the most likely reasons is that it created a lot of crevasses on the surface, and those crevasses are pipelines for the surface meltwater to go down into the bottom of the glacier. Now, water comes down more easily and effectively reduces the friction, so the glacier can keep sliding fast, and even faster if the climate gets further warmed up.”
Zheng intends to test the new model on a few of Antarctica’s marine-terminating glaciers. Anyone may now replicate Zheng’s findings by running his data through the model equations and Python code through a new online platform called Jupyter Book, which he thinks will set a standard for publishing big data research in the future.
The work was partially supported by the Jupyter meets the Earth project, which is funded by the National Science Foundation’s EarthCube program (1928406, 1928374).
