A massive Antarctic glacier, which could raise global sea levels by up to two feet if it melts, is far more exposed to warm ocean water than previously believed, according to a study published Monday.
Thwaites Glacier, the world’s widest, bobs up and down on daily tides. As it lifts up, warm seawater is shooting farther under the ice than scientists thought — up to 6 kilometers, or 3.7 miles, according to satellite data. This has the potential to substantially increase the area over which the glacier is melting, scientists found.
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The degradation of Thwaites, popularly known as the “doomsday glacier,” means the warm ocean could eat further into the West Antarctic ice sheet and bring with it the potential for massive sea level rise.
“The water is able to penetrate beneath the ice over much longer distances than we thought,” said Eric Rignot, a scientist with the University of California at Irvine and NASA’s Jet Propulsion Laboratory, who led the research. “It’s kind of sending a shock wave down our spine to see that water moving kilometers.”
Rignot’s research team had previously documented this extensive tidal pulsing of seawater at Petermann Glacier, one of the largest outflows of ice in Greenland. But Thwaites makes Petermann look small. It is 80 miles wide where it touches the ocean, versus about 10 miles for Petermann.
The new study was published Monday in the Proceedings of the National Academy of Sciences. Authors work at the University of California at Irvine, the NASA Jet Propulsion Laboratory at the California Institute of Technology, the University of Waterloo in Canada, and the Finnish firm ICEYE, which provided the satellite observations.
Rignot said he believes the process he described in Monday’s paper will speed up the results of models that scientists use to predict future sea levels.
Thwaites is currently hooked to the ocean floor by two ocean ridges underneath the glacier. But when the tide lifts the glacier up, the new research found, seawater is getting over or around one of them. If Thwaites became untethered from those ridges, it would allow warm ocean water to enter an area where the seafloor dips downward into very deep regions toward the center of West Antarctica.
The new study “confirms that this process of pushing water up underneath the glacier is going on, which has been seen with a few other techniques, but never with this dynamic resolution,” said Britney Schmidt, a scientist at Cornell University who has studied a similarly deep undersea and under-ice region of Thwaites via a submersible robot, named Icefin.
Schmidt says that the ability of water to squeeze in this way, even running up a slope that the ice has been hooked onto, is a new factor increasing the glacier’s instability. In the past, scientists have mainly emphasized that glaciers retreat rapidly when perched on downhill slopes. Thwaites is currently doing so while moored up an uphill slope.
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Several other experts consulted by The Washington Post said the new research raises concerns, but it remains unknown exactly how fast Thwaites will melt.
“These new observations are truly exceptional,” said Mathieu Morlighem, an expert at Dartmouth College who uses ice sheet simulations, or models, to study the future of Thwaites and other glaciers.
But he said that these simulations, the chief tool for determining how much ice Thwaites can lose and how quickly, can’t immediately be updated with this type of information. The process would need to be better understood first.
“We don’t know how fast this intrusion of water is melting the ice,” Morlighem said. “It could be small, in which case we would not need to include this process in models.” However, he said, the process could also be large and melt through more than ten meters (nearly 33 feet) of ice thickness per year.
John Anderson, a geologist at Rice University who has studied Thwaites Glacier, said conditions at what is known as the grounding line — a long ice perimeter where the glacier sits on the sea floor and is exposed to the ocean — are “sensitive to even minor fluctuations caused by tides.” Studies of glacier movements from the distant past suggest that these changes can happen quickly, he said.
But, Anderson said, knowing exactly how fast warm water will cause melting requires detailed mapping of the seafloor, which remains inadequate for the task in a place as remote as Thwaites.
Monday’s study also suggests that the grounding line at Thwaites is constantly moving over large areas. Its general tendency, however, remains backward.
That’s because the intruding seawater is several degrees warmer than the freezing point of ice at the depths and pressures where Thwaites rests on the seabed. The most extensive intrusions are only of thin layers of water, but Rignot thinks that can still do a lot of damage.
“It’s a very thin layer, but it comes from the ocean, it contains heat, it’s salty, it’s coming at high speed,” he said.
Thwaites Glacier, the world’s widest, bobs up and down on daily tides. As it lifts up, warm seawater is shooting farther under the ice than scientists thought — up to 6 kilometers, or 3.7 miles, according to satellite data. This has the potential to substantially increase the area over which the glacier is melting, scientists found.
Sign up for the Climate Coach newsletter and get advice for life on our changing planet, in your inbox every Tuesday.
The degradation of Thwaites, popularly known as the “doomsday glacier,” means the warm ocean could eat further into the West Antarctic ice sheet and bring with it the potential for massive sea level rise.
“The water is able to penetrate beneath the ice over much longer distances than we thought,” said Eric Rignot, a scientist with the University of California at Irvine and NASA’s Jet Propulsion Laboratory, who led the research. “It’s kind of sending a shock wave down our spine to see that water moving kilometers.”
Rignot’s research team had previously documented this extensive tidal pulsing of seawater at Petermann Glacier, one of the largest outflows of ice in Greenland. But Thwaites makes Petermann look small. It is 80 miles wide where it touches the ocean, versus about 10 miles for Petermann.
The new study was published Monday in the Proceedings of the National Academy of Sciences. Authors work at the University of California at Irvine, the NASA Jet Propulsion Laboratory at the California Institute of Technology, the University of Waterloo in Canada, and the Finnish firm ICEYE, which provided the satellite observations.
Rignot said he believes the process he described in Monday’s paper will speed up the results of models that scientists use to predict future sea levels.
Thwaites is currently hooked to the ocean floor by two ocean ridges underneath the glacier. But when the tide lifts the glacier up, the new research found, seawater is getting over or around one of them. If Thwaites became untethered from those ridges, it would allow warm ocean water to enter an area where the seafloor dips downward into very deep regions toward the center of West Antarctica.
The new study “confirms that this process of pushing water up underneath the glacier is going on, which has been seen with a few other techniques, but never with this dynamic resolution,” said Britney Schmidt, a scientist at Cornell University who has studied a similarly deep undersea and under-ice region of Thwaites via a submersible robot, named Icefin.
Schmidt says that the ability of water to squeeze in this way, even running up a slope that the ice has been hooked onto, is a new factor increasing the glacier’s instability. In the past, scientists have mainly emphasized that glaciers retreat rapidly when perched on downhill slopes. Thwaites is currently doing so while moored up an uphill slope.
Follow Climate & environment
Several other experts consulted by The Washington Post said the new research raises concerns, but it remains unknown exactly how fast Thwaites will melt.
“These new observations are truly exceptional,” said Mathieu Morlighem, an expert at Dartmouth College who uses ice sheet simulations, or models, to study the future of Thwaites and other glaciers.
But he said that these simulations, the chief tool for determining how much ice Thwaites can lose and how quickly, can’t immediately be updated with this type of information. The process would need to be better understood first.
“We don’t know how fast this intrusion of water is melting the ice,” Morlighem said. “It could be small, in which case we would not need to include this process in models.” However, he said, the process could also be large and melt through more than ten meters (nearly 33 feet) of ice thickness per year.
John Anderson, a geologist at Rice University who has studied Thwaites Glacier, said conditions at what is known as the grounding line — a long ice perimeter where the glacier sits on the sea floor and is exposed to the ocean — are “sensitive to even minor fluctuations caused by tides.” Studies of glacier movements from the distant past suggest that these changes can happen quickly, he said.
But, Anderson said, knowing exactly how fast warm water will cause melting requires detailed mapping of the seafloor, which remains inadequate for the task in a place as remote as Thwaites.
Monday’s study also suggests that the grounding line at Thwaites is constantly moving over large areas. Its general tendency, however, remains backward.
That’s because the intruding seawater is several degrees warmer than the freezing point of ice at the depths and pressures where Thwaites rests on the seabed. The most extensive intrusions are only of thin layers of water, but Rignot thinks that can still do a lot of damage.
“It’s a very thin layer, but it comes from the ocean, it contains heat, it’s salty, it’s coming at high speed,” he said.
