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Greenland glaciers may lose more ice than expected, raising sea level rise concerns



But what experts have less information about is how these vital glaciers have changed in the past, especially in the centuries before satellite imagery. Understanding how glaciers have responded to past climate change may affect scientists’ predictions of how they may respond to future warming.

Researchers have found that glaciers in Greenland are very sensitive to climatic conditions and lost ice in the late 19th and early 20th centuries at speeds that are rivals or exceed those observed today. As the planet – and the Arctic in particular – is expected to warm much more this century, scientists warn that their findings show that the loss of ice in Greenland could exceed even the worst forecasts.

David Holland, a professor of mathematics and environmental science at New York University and co-author of the study, said the team̵

7;s findings showed that the Arctic “suffered one or two blows in terms of drought loss and sea ice cover in a warming world.” “

Using historical photographs of the Jacobshavn, Hellheim and Kangerlusuac glaciers, the team calculated the loss of ice from 1880 to 2012. They estimated that the amount of ice lost by these three glaciers alone led to an 8.1-millimeter rise in sea level. Holland said that while the three glaciers are important in their own right, they also serve as proxies for most of Greenland’s other glaciers, giving scientists a glimpse of how the entire ice sheet behaves.

Greenland's ice sheet is melting as fast as it has at any time in the last 12,000 years, according to a study

Greenland’s ice sheet is a dynamic place that is constantly shifting and moving. If we think of the interior of the ice sheet as a mountain lake, Moon says, these source glaciers are streams fluttering from the lake, carrying ice from it and in many cases into the ocean. When the ice breaks off from the glacier and lands in the ocean, it raises sea levels.

“These three glaciers are among the fastest moving in Greenland. When we think of these glaciers all over Greenland, acting as conveyor belts (moving ice to the ocean), these are some of the fastest, largest conveyor belts. on the ice sheet, “said Tuila Moon, a deputy lead scientist at the National Snow and Ice Data Center in Boulder, Colorado, who was not involved in the study.

Glaciers also have enough ice to raise global sea levels by about 1.3 meters.

The loss of ice over time is due to natural changes in winds and ocean currents, and as warm waters approach glaciers, they melt, the Netherlands said. But man-made warming is changing the climate and changing the way winds and oceans interact with the ice sheet and therefore affect the amount of ice loss.

The team found that the ice loss rates for the Jacobshavn Glacier in the early 1900s were comparable to the huge rate of loss seen today, and for the Kangerlusuak Glacier, the ice between 1880 and 1930 was actually higher than it is today.

This is important because it shows that glaciers are losing large amounts of ice at a time when global temperatures were lower than they are today.

In the worst-case scenario, in which humans continue to increase the concentrations of these heat-retaining gases in the atmosphere, the planet could warm by 3.7 degrees Celsius (6.66 degrees Fahrenheit) by the end of this century.

If glaciers have already suffered heavy ice losses when atmospheric and ocean temperatures were lower – and the planet is set to warm even more in the future with high emissions – scientists say their findings could mean models used to predict future ice losses in Greenland may underestimate how much will be lost by the end of the century.

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This may also affect current forecasts of sea level rise.

Rising seas are already creating problems in very low-lying coastal areas. And for places like New York and Shanghai, 1 meter or more of sea level rise can cause a catastrophe. Another recent study found that rising seas could cost the global economy $ 14.2 trillion in lost or damaged assets by the end of the century and expose 287 million people to occasional floods, up from 171 million today.

“I think when it comes to the pace of change in Greenland and really with ice all over the world, we are already in a state of five alarms,” ​​Luna said. “And this document is another document from this monstrous pile that says that these are really serious changes, they are happening very quickly and we need to take action as soon as possible so that we can try to reduce the speed of change. in the future.”

In the study, the researchers said that the possible underestimation of ice loss is likely “not limited to these three glaciers” and that it is important for models to capture rapid retreat of glaciers as a result of human-induced warming of our oceans and atmosphere. are the main driver of weight loss. “

The team hopes that their findings on how glaciers are sensitive to climate change will help increase the reliability of future ice loss forecasts.

“The Arctic is losing ice, and as you look more closely at the last century, you see periods of more loss and less loss, but always loss,” Holland said. “With the increase in warming, which is expected to continue in the future, increased ice loss can be expected with potentially serious negative consequences for coastal cities around the world.”

Ivana Kotasova of CNN contributed to this report.


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