NASA’s Oceans Melting Greenland airborne mission discovered that Greenland’s glaciers that vacant into the ocean, like Apusiaajik Glacier proven right here, are at higher danger of speedy ice loss than beforehand understood. Credit score: NASA/JPL-Caltech
To find out how ocean water is melting glaciers, NASA’s Oceans Melting Greenland mission extensively surveyed the shoreline of the world’s largest island.
Crucial factor to recollect about NASA’s Oceans Melting Greenland mission, which ended Dec. 31, 2021, could also be its identify: OMG proved that ocean water is melting Greenland’s glaciers at the very least as a lot as heat air is melting them from above. As a result of ice loss from Greenland’s ice sheet at the moment contributes extra to the worldwide rise of the oceans than some other single supply, this discovering has revolutionized scientists’ understanding of the tempo of sea degree rise within the coming many years.
These new, distinctive measurements have clarified the doubtless progress of future ice loss in a spot the place glaciers are melting six or seven instances sooner immediately than they had been solely 25 years in the past. If all of Greenland’s ice sheet had been to soften, international sea ranges would rise by about 24 toes (7.4 meters).
OMG’s six-year discipline marketing campaign in Greenland has modified scientists’ understanding of how briskly the worldwide sea degree will rise in coming many years. Credit score: NASA/JPL-Caltech
However that’s simply the tip of the iceberg within the story of this small plane- and boat-based mission. In six years of operations, OMG made the primary scientific measurements alongside many miles of probably the most distant shoreline within the Northern Hemisphere. The mission carried out probably the most full survey of the seafloor round Greenland’s shoreline, together with dozens of beforehand uncharted fjords (cliff-lined inlets clogged with icebergs from disintegrating glaciers), and measured how the ocean temperature modified from place to put, yr to yr, and high to backside. To get this distinctive dataset, mission planes logged sufficient air miles round and over Greenland to circle the globe greater than 13 instances.
Preparation
Greater than 220 glaciers circulate from Greenland into the ocean. Earlier than OMG, scientists figured the ocean water swirling round and beneath these glaciers needed to be contributing to their ice loss. However how a lot?
Satellite tv for pc observations of sea floor temperature weren’t a lot assist in answering that query. Round Greenland, the highest layer of the ocean is extraordinarily chilly and never very salty, containing quite a lot of water from the Arctic, the freshest of oceans. A shallow glacier that solely touches this layer melts slowly. However a whole lot of toes beneath, the ocean is hotter and saltier. A deep-seated glacier is eaten away by the hotter water, dropping ice 4 or 5 instances as quick as a shallow one.
NASA’s Gulfstream III was one in every of a number of analysis plane that OMG used through the mission’s six-year discipline marketing campaign. Airports in Greenland, Iceland, and Norway served as bases for analysis flights. Credit score: NASA/JPL-Caltech
The one solution to discover out any glacier’s danger is to go to Greenland and measure the glacier and the seafloor and water in entrance of it. Scientists had been learning particular person glaciers that means for years, however Josh Willis, principal investigator of OMG at NASA’s Jet Propulsion Laboratory in Southern California, needed to get the entire image: to measure all 220-plus glaciers for 5 years – the size of time accessible to missions funded by NASA’s Earth Ventures airborne analysis program.
“After we began to design OMG, we requested ourselves, ‘Can we do an experiment in 5 years that may inform us in regards to the subsequent 50?’” Willis mentioned. Outcomes have proved that they may. NASA even allowed them a sixth yr of fieldwork to look at surprising, speedy swings in water temperatures off Greenland’s west coast.
Operation
The mission’s first job was to map the seafloor across the island to see the place deep, heat water can attain glaciers. A contractor accomplished a lot of the mapping utilizing a analysis boat, and OMG Deputy Principal Investigator Eric Rignot of JPL and the College of California, Irvine led smaller surveys in following years to fill in lacking sections.
To measure the ocean temperature and salinity right down to the seafloor, Willis ran a summer time airborne marketing campaign that dropped about 250 probes every year into the ocean at strategic places across the whole shoreline. Six summers of flying over the distant Arctic could sound extra like an journey than a analysis challenge, however, Willis mentioned, “It’s solely an journey looking back. Whilst you’re in it, you might have your head down and also you’re working as onerous as you may.” For the scientists, the information streaming into their laptop from the probes was pleasure sufficient.
The detailed maps and temperature knowledge collected by OMG present that two to 4 instances as many glaciers sit in water that's a number of levels hotter than beforehand thought and, thus, are at greater danger than anybody knew. Researchers understood that a couple of third of Greenland’s glaciers account for half of its ice loss; OMG discovered that every one of those culprits attain down into heat water. Local weather fashions that don’t account for the nice and cozy water’s results underestimate glacial ice loss by at the very least an element of two – in different phrases, lacking half the ocean degree rise from this supply.
Collaboration
OMG’s groundbreaking knowledge has influenced many sorts of Arctic research moreover oceanography. For instance, Kristin Laidre of the College of Washington is an internationally identified skilled on narwhals, Arctic whales with a tusk-like protruding tooth. She and Ian Fenty, an OMG co-principal investigator at JPL, developed a challenge that advantages each marine biologists and oceanographers: a analysis cruise to put OMG probes and acoustic sounders that file the presence of narwhals in entrance of West Greenland glaciers.
The probe knowledge gives a close-up view of how a lot ocean circumstances can range in a small space, and Laidre hopes that, together with the sounder knowledge, it is going to assist clarify why sure glacier fronts are particularly engaging to narwhals. “We biologists can get a greater understanding of animals and populations by working with bodily scientists,” she mentioned, referring to the OMG group. “To have a gaggle of scientists who need to collaborate is admittedly nice.”
Continuation
The top of the mission doesn’t imply the tip of all new knowledge from the Greenland ocean. In 2021, the group dropped a couple of longer-lived probes in areas the place adjustments in ocean temperatures or circulation are usually not totally understood. These probes “winter over” beneath the floor, persevering with to bob up and down by the water to gather knowledge that might be learn remotely when the ice melts subsequent summer time.
And scientists in lots of fields will proceed to attract on OMG’s observations for his or her analysis. To this point, about half of peer-reviewed journal articles utilizing the information are written by researchers exterior the mission’s science group – an unusually giant portion. “We’re seeing much more science than we initially deliberate,” Willis mentioned. “These papers aren’t going to cease.”
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