The so-called “doomsday” ice sheet of Antarctica – the Thwaites Glacier – is melting faster than previously believed, one of several recent changes in ice formation throughout the southern hemisphere that are prompting experts to rethink projections about how much, and how fast, the oceans are rising, according to two reports released this month.
One of those reports is a new study, involving a team of glacier experts led by researchers at UC Irvine. It shows how comparatively warm saltwater sloshes up between Thwaites’ ice and its supporting land mass, Antarctica, prompting that glacier to melt at a rate faster than previously believed.
Thwaites is roughly the size of Florida, so any acceleration of its long-term erosion could have profound effects on everything from marine life and ocean currents to the future of low-lying communities from Seal Beach to the Maldives. In all, if Thwaites completely melts, it could prompt the world’s oceans to rise by nearly 2 feet.
But UCI scientists weren’t surprised to see Thwaites shrink, having tracked at least some meltdown there over several decades. The glacier has been linked to about 4% of the increase already recorded in oceans around the world over the past 40 years.
Instead, scientists were surprised to learn why Thwaites is melting, and the rate at which it’s happening.
Using radar-generated images from last spring, and X-ray technology to essentially peek under the thick ice, researchers saw that the same process that eats up floating ice sheets near the North Pole also can chew into ground-based ice sheets and glaciers, such as Thwaites, that cover Antarctica and much of Greenland.
“We know that warm (ocean) water eats ice from below when that ice is floating,” said Eric Rignot, a professor who teaches earth sciences at UCI and the lead author of the report published Monday, May 20 in the journal “Proceedings of the National Academy of Sciences.”
Eric Rignot, UCI professor of Earth system science in Antarctica. (Courtesy Eric Rignot)
“What we did not know is that (the same process) was already doing that, over very large areas, beneath grounded ice,” Rignot added.
“Because tides lift up the glaciers, this allows sea water to go very far beneath the glacier; much farther than we thought.”
The long-term meltdown at Thwaites, specifically, also poses a second threat.
The glacier, located in west Antarctica, serves as a huge, natural dam, blocking runoff from some of the continent’s other melting glaciers from flowing into the ocean. Combined, the flow from those glaciers and a liquified Thwaites could boost the world’s oceans by up to 10 feet, a jump that would be nearly twice anything contemplated in current federal forecasts.
The 2022 Sea Level Rise Technical Report issued by the National Oceanic and Atmospheric Administration notes that ocean levels near the coasts of North America have risen by about a foot over the past century, and projects the trend to continue for at least the next 75 years, with the rate and amount of those changes based on how much carbon is burned and emitted into the atmosphere. On the low end, NOAA forecasts the world’s oceans to rise by about another foot by 2100; the high-end estimate is a gain of about 6.6 feet.
Both forecasts were made before UCI issued its report on Thwaites.
“Thwaites is the most unstable place in the Antarctic and contains the equivalent of 60 centimeters of sea level rise,” said Christine Dow, a professor of glaciology at the University of Waterloo, Ontario and a co-author of the report.
“The worry is that we are underestimating the speed that the (Thwaites) glacier is changing, which would be devastating for coastal communities around the world.”
The UCI study came on the heels of a separate report showing that there’s less floating ice near the South Pole than any time in the past 45 years.
The National Snow and Ice Data Center reported this month that early season build-up of ice floating in the ocean near Antarctica is down by about 15%, a gap roughly as big as Texas. Though it’s expected that more ice will form later in the year (ice builds up in the ocean near Antarctica on a seasonal basis, typically maxing out in October and November) scientists say the pace would have to pick up dramatically to reach a level considered normal.
Such dire projections about the southern hemisphere are relatively new.
Until about 10 years ago, researchers who tracked rapid declines in the amount of ice floating in the Arctic Ocean and other parts of the northern hemisphere were puzzled by not seeing a matching problem on the other side of the planet. In fact, in several years of the early 2000s, the annual ice sheets near Antarctica increased or at least held steady, even as other parts of the world melted.
That began to shift during a two-year window starting in 2014. Since then, the oceans near the South Pole have been progressively less icy, hitting all-time lows in 2017, 2022 and last year.
Rignot, who told Axios this month that he believed the lull in South Pole ice loss during the early 2000s was a result of a change in the ozone hole and stronger winds, said the new trend probably is a result of global warming.
“Now, we can say with a bit more certainty that this is not anomalous behavior — it’s a change of state,” Rignot said.
The decline in floating ice – unlike land-based glaciers – isn’t a huge factor in making the oceans rise. Much of the floating ice, after all, is already in the water.
But less ice near the South Pole would dramatically affect the formation of plankton and other microscopic sea life that’s critical to the region’s ecosystem. Everything from whales to penguins – and the humans that depend on fish caught in the Southern Hemisphere – could be harmed as ice becomes more scarce near Antarctica.
None of this is inevitable. Scientists involved in the UCI study said changes in carbon consumption could alter current trajectories.
They also argue that further research of the glaciers in Antarctica – which could become huge game-breakers in how much the ocean rises over the next three to six decades – is essential.
“At the moment we don’t have enough information to say one way or the other how much time there is before the ocean water intrusion is irreversible,” Dow said.
“By improving the models and focusing our research on these critical glaciers, we will try to get these numbers at least pinned down for decades versus centuries. This work will help people adapt to changing ocean levels, along with focusing on reducing carbon emissions to prevent the worst-case scenario.”
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