This Greenland ice sheet melting rate could mean even worse sea level rise

Scientists studying one of Greenland’s largest glaciers say it’s melting faster than expected in its most vulnerable area, a worrying sign that sea-based glaciers could contribute to sea-level rise faster than currently predicted.

Scientists fear that the phenomenon seen at Petermann Glacier could happen to other glaciers in both Greenland and Antarctica, leading to faster and more dramatic global sea level rise – “double” what is currently expected from glaciers. The study was released on Monday.

Using satellite measurements of its surface, the researchers found that Peterman was bobbing up and down, dramatically shifting its seabed moorings in response to tides. All of this movement has carved out a large cavern at the base of the glacier and allowed warm water to continue to extend beneath it. As the glacier moves up and down, the water rushes more than a mile, thinning the ice 250 feet a year in some places.

“Seawater continues to be scoured several kilometers below the glacier,” said glaciologist Eric Rignot, one of the study’s authors and the Jet Propulsion Laboratory at the California Institute of Technology, Irvine.

“We think it will change the sea level projections quite a bit,” he said. The study was published Monday in the Proceedings of the National Academy of Sciences.

The Petermann glacier is the next big thing in the context of climate change that could break our greenhouse gas emissions. A vast glacier about ten miles wide One of the many major outlets where ice flows from the interior of Greenland into the ocean. All in all, a massive chunk of ice lined up behind Peterman If all of this melted, it could raise global sea levels by more than 1 foot.

Peterman hasn’t changed as much as some other Greenland glaciers, perhaps in part because it’s so far north. But it has seen important changes.

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Petermann lost two large chunks of ice from its floating ice shelf in 2010 and 2012, causing the shelf to lose a third of its area. It has not recovered since then.

The core of the glacier also began to move backwards Its base line — where it sits on the floor of a deep fjord — retreated inland more than 2 miles toward the interior of Greenland. This has occurred in response to the warming of the water in the fjord in front of the glacier. According to Rignot, the warming has only been a fraction of a degree, but the water is now slightly above zero degrees Celsius. But this is more than enough heat to melt ice, especially at the depths and pressures found in underground lines.

At the same time, the ice began to flow out at a much faster rate, meaning that Peterman is losing a few billion tons of ice to the ocean each year from a more or less steady state. It’s not that big compared to some of the other big glaciers in Antarctica or Greenland, but it’s just the beginning.

All these reflect changes in the base line, which are very difficult to notice. But satellites can detect two changes in the glacier’s surface elevation, which can be used to predict what’s happening below and how the glaciers respond to cycles in tides.

This is exactly what the new research captures in Petermann – showing that tidal cycles have far-reaching implications for glacier melt. Satellites showed it There is no real base “line”—rather, there is a broad zone more than a mile long over which the glacier moves back and forth across the seafloor. This movement accelerates melting by allowing seawater to mix near and even beneath the glacier.

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The research also found that a huge hole – 650 feet high – has now been drilled into the center of the landing strip. It covers an area of ​​nearly 8 square miles, and in this area, the sea can intrude and melt without the aid of waves that move and lift the glacier.

All of this, according to the researchers, has far-reaching implications — we may need to adjust our current models to account for rapid melting along underground lines of large glaciers. In turn, the study suggests that sea-level rise projections of these behemoths could “potentially double.”

“Probably many other glaciers are in that situation, with tidal scour,” Rignot said. Overall, he believes Peterman is a good analogy for what’s happening in Antarctica, which is also at greater risk of ice loss than Greenland.

The research was conducted by scientists from three US institutions – the Jet Propulsion Laboratory at the University of California, Irvine, the California Institute of Technology, and the University of Houston – in collaboration with international colleagues from institutions in China, Finland and Germany. and Italy.

Many scientists Not linked to course Impressed by the new measurements reached by The Post, but not entirely convinced of their implications.

“The reported melt rates are very large, much larger than anything we suspected in this region,” said Helen Serosi, a glaciologist at Dartmouth College who uses models to study glaciers and sea-level rise.

However, Seroussi said the models researchers use to predict sea-level rise — complex equations used to predict how glaciers around the world will respond to warmer oceans and winds — won’t change immediately based on the current results. study

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“We are years away from properly implementing these processes in numerical models,” Serosi said. “It is important to understand that there are always long delays between the discovery of a new process and its inclusion in numerical models, as these processes must be fully understood from a physical point of view,” further research is needed.

In particular, Serosi said, the process in question It is not generally included because the extent to which it works is not fully understood. Until that happens, some models may show more ice loss because of it, as they represent play over a larger region.

Andreas Muenzo, a University of Delaware scientist studying the Petermann Glacier, also had some cautionary notes.

“I like the idea of ​​the ‘tidal heartbeat’ of the glacier’s landing zone, where the glacier is penetrated by warm water during the incoming tide and drained by cold water during the outgoing tide,” Muenzo said.

However, he noted, “the very high melting rates are real, but they are estimated over very small areas.”

“My main point is that models need to be improved,” Muenchow concluded. This study puts a sharp focus on what processes we need to study near floating glaciers in Greenland or Antarctica if we want to use models to predict sea level rise in the future.”

Overall, the new study underscores again that we don’t know how quickly one of the biggest effects of climate change — sea-level rise from the melting ice sheets of Greenland and Antarctica — will happen. We’re still discovering new details — and new reasons to think it could be faster than expected.

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