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https://www.nationalgeographic.com/environment/2019/07/alaskan-glaciers-melting-faster-than-previously-thought/ PUBLISHED July 25, 2019
A new way of measuring how some glaciers melt below the surface of the water has uncovered a surprising realization: Some glaciers are melting a hundred times faster than scientists thought they were.
In a new study published today in Science, a team of oceanographers and glaciologists unpeeled a new layer of understanding of tidewater glaciers—glaciers that end in the ocean—and their dynamic processes.
“They’ve really discovered that the melt that’s happening is fairly dramatically worse than some of the assumptions we’ve had,” says Twila Moon, a glaciologist at the National Snow and Ice Data Center at the University of Colorado-Boulder who was uninvolved with the study.
A warming climate accelerates glacier melting across the globe, potentially through melting across the surface of the glacier, but also through underwater melting.
Glaciers can extend hundreds of feet below the surface, explained Ellyn Enderlin, a glaciologist at Boise State University who was not involved with the study. Finding higher rates of submarine melting tells us that “glaciers are a lot more sensitive to ocean change than we’ve thought.” https://www.nationalgeographic.com/...rld-mountain-glaciers-melting-sea-level-rise/
LeConte was an ideal glacier to study because it is really accessible for a tidewater glacier, Sutherland said. A complex environment, the project required so many lines of data that teams of oceanographers and glaciologists collected data simultaneously at the glacier.
Scientists spent weeks aboard the boat working 24 hours a day, with each scientist taking 12-hour shifts.
From the 80-foot MV Stellar, oceanographers performed sonar surveys underwater, like the ones used to measure ocean depths. Instead of directing the sonar toward the ocean floor, though, they angled the sonar to collect the 3D underwater portion of the glacier face.
Scientists repeated their observations during two summers, obtaining multiple scans each trip.
Simultaneously, a team of glaciologists camped on a ridge overlooking the glacier. They “babysat” a delicate radar instrument to measure the natural movement of the glacier. Time-lapse cameras were used to measure glacier flow so that they knew how fast the ice moves toward the ocean, says Jason Amundson, a glaciologist and co-author of the study at University of Alaska Southeast.
From the datasets, researchers were able to calculate a total melting rate for the underwater portion of the glacier: two orders of magnitude higher than they expected.
They calculated that the glacier melted underwater at a rate of almost 5 feet per day in May and up to 16 feet per day in August. Later in the season, the warmer water increased the underwater melting. Usually less than 6 degrees Celsius, water in LeConte Bay is warm relative to the ice, and even other fjords around the world.
“Submarine melting may matter everywhere,” says Enderlin.
Tidewater glaciers are some of Alaska's biggest. These “glaciers can change much more quickly than valley glaciers because of the processes that are happening right where the glacier flows into the ocean,” says Amundson.
If you turn the knob of climate up, like with climate change, says Sutherland, you increase the temperature of water and air and you will certainly get more melting.
“These observations pretty clearly show us that there are things that we’ve been missing,” says Moon. “It’s a real call to action,” to better understand how these systems work.
TRUMP
A new way of measuring how some glaciers melt below the surface of the water has uncovered a surprising realization: Some glaciers are melting a hundred times faster than scientists thought they were.
In a new study published today in Science, a team of oceanographers and glaciologists unpeeled a new layer of understanding of tidewater glaciers—glaciers that end in the ocean—and their dynamic processes.
“They’ve really discovered that the melt that’s happening is fairly dramatically worse than some of the assumptions we’ve had,” says Twila Moon, a glaciologist at the National Snow and Ice Data Center at the University of Colorado-Boulder who was uninvolved with the study.
A warming climate accelerates glacier melting across the globe, potentially through melting across the surface of the glacier, but also through underwater melting.
Glaciers can extend hundreds of feet below the surface, explained Ellyn Enderlin, a glaciologist at Boise State University who was not involved with the study. Finding higher rates of submarine melting tells us that “glaciers are a lot more sensitive to ocean change than we’ve thought.” https://www.nationalgeographic.com/...rld-mountain-glaciers-melting-sea-level-rise/
LeConte was an ideal glacier to study because it is really accessible for a tidewater glacier, Sutherland said. A complex environment, the project required so many lines of data that teams of oceanographers and glaciologists collected data simultaneously at the glacier.
Scientists spent weeks aboard the boat working 24 hours a day, with each scientist taking 12-hour shifts.
From the 80-foot MV Stellar, oceanographers performed sonar surveys underwater, like the ones used to measure ocean depths. Instead of directing the sonar toward the ocean floor, though, they angled the sonar to collect the 3D underwater portion of the glacier face.
Scientists repeated their observations during two summers, obtaining multiple scans each trip.
Simultaneously, a team of glaciologists camped on a ridge overlooking the glacier. They “babysat” a delicate radar instrument to measure the natural movement of the glacier. Time-lapse cameras were used to measure glacier flow so that they knew how fast the ice moves toward the ocean, says Jason Amundson, a glaciologist and co-author of the study at University of Alaska Southeast.
From the datasets, researchers were able to calculate a total melting rate for the underwater portion of the glacier: two orders of magnitude higher than they expected.
They calculated that the glacier melted underwater at a rate of almost 5 feet per day in May and up to 16 feet per day in August. Later in the season, the warmer water increased the underwater melting. Usually less than 6 degrees Celsius, water in LeConte Bay is warm relative to the ice, and even other fjords around the world.
“Submarine melting may matter everywhere,” says Enderlin.
Tidewater glaciers are some of Alaska's biggest. These “glaciers can change much more quickly than valley glaciers because of the processes that are happening right where the glacier flows into the ocean,” says Amundson.
If you turn the knob of climate up, like with climate change, says Sutherland, you increase the temperature of water and air and you will certainly get more melting.
“These observations pretty clearly show us that there are things that we’ve been missing,” says Moon. “It’s a real call to action,” to better understand how these systems work.
TRUMP
