Greenland’s vast ice sheet is known to have been shrinking due to warming caused by climate change, especially since the 1990s. It’s a fate shared not only by the Antarctic ice sheet but also by glaciers around the world. Now, a new study shows that about 20 percent more Greenland ice sheet has disappeared than previously estimated.
Lost ice is breaking off and melting from the edges of Greenland’s surrounding glaciers. In a new study, Published in Nature magazine on Wednesdayprovides a detailed description of a process that scientists knew was happening but struggled to comprehensively measure.
“Nearly all of Greenland’s glaciers are retreating. And that story is true everywhere you look,” said Chad Green, a glaciologist at NASA’s Jet Propulsion Laboratory and lead author of the study. Stated. “This withdrawal is happening everywhere at the same time.”
The edges of these glaciers are typically located below sea level within deep fjords, so their retreat does not have a large direct impact on sea level rise. But melting ice still results in an influx of freshwater, affecting global climate models and projections and the systems of ocean currents that regulate temperatures on both sides of the Atlantic Ocean.
Dr. Green’s team combined more than 200,000 observations of glacier termini covering nearly all of Greenland, based on satellite images taken from 1985 to 2022. The researchers used observations from existing public datasets and combined them to create a comprehensive bird’s-eye view. How the edge of Greenland’s ice sheet has shrunk over the past 40 years.
“They provide a very important new data set that captures the area of the entire Greenland Ice Sheet.,” Arizona State University climate scientist Laura Larocca, who also studies Greenland’s glaciers, said she was not involved in the project.
Previous estimates of changes in the size of the Greenland ice sheet have been based on three types of measurements: the height of the ice sheet’s surface, the speed of the ice past a fixed location, and the gravity exerted by the ice sheet’s mass. Ta.
Combining some of these estimates, scientists believe that Greenland’s total almost 5 trillion tons Ice since 1992.
These traditional methods provide insight into how much ice sheets are contributing to sea level rise. 13mm, or 0.5 inch, so far. But they don’t capture everything that’s happening at the base and margins of the hundreds of glaciers that feed the island’s many fjords. This process, called glacier terminal retreat, will result in the loss of an additional 1 trillion tonnes of ice, according to a new study.
The amount is approximately equivalent to one ice cube. Covers an area larger than Manhattan and higher than Mount Everestaccording to the European Space Agency.
Of the more than 200 glaciers included in the study, only one had expanded definitively since 1985. That increase was small compared to losses elsewhere.
Erosion of these glacier termini has an indirect effect on sea level. Dr Green compared the retreat of a glacier terminal to unplugging a drainpipe, saying the entire glacier flows faster and thinner, accelerating the melting of the parts above sea level.
So while the study isn’t measuring the direct impact on sea level rise, “it’s probably measuring the causes of sea level rise,” he said.
Greenland’s additional lost ice is important for other reasons as well.
Melting ice adds large amounts of fresh water to the ocean, potentially weakening an important ocean current system called the Atlantic Meridional Overturning Circulation. This system includes the Gulf Stream, which brings warm tropical water from the southeast coast of the United States across the Atlantic Ocean to Europe, contributing to Europe’s relatively mild temperatures.
The fraying edges of Greenland’s glaciers have been somewhat overlooked as scientists focus on the pressing issue of rising sea levels. Vincent Bergens, a glaciologist at Busan National University’s IBS Center for Climate Physics in South Korea, who reviewed the study, said scientists will gain a better understanding of the entire climate system and how global warming is distributed in the atmosphere. He said it would be helpful. ocean and ice sheets.
This is a topic that is “rarely addressed,” but “an important one,” Dr. Bergens said.