The ice sheet in Greenland lost about one-fifth more ice mass in the last forty years than previously estimated, researchers at NASA’s Jet Propulsion Laboratory in South California reported in a new paper published on Wednesday.
Icebergs are falling into the ocean at an accelerating rate, and a majority of the glaciers on the landmass have retreated significantly. However, the additional ice loss only has an indirect impact on sea levels, but it could have massive implications for ocean circulation in the future.
For the research published in the journal Nature on Wednesday, the researchers analysed the retreat around the edges of the ice sheet from 1985 to 2022. They drew from nearly a quarter million pieces of satellite data on glacier positions. Of the 207 glaciers they comprehensively looked at, 179 retreated significantly since 1985, 27 kept their positions and one advanced slightly.
Most of the ice loss came from below the sea level in the fjords on the periphery of Greenland. They were once occupied by glacial ice but many developed coastal valleys filled with seawater. This means that the ice that broke off made a very small net contribution to sea level. But this loss did accelerate the movement of ice flowing down from higher elevations, which will eventually lead to sea level rise.
“When the ice at the end of a glacier calves and retreats, it’s like pulling the plug out of the fjord, which lets ice drain into the ocean faster,” said Chad Greene, a glacier scientist at JPL and the study’s lead author, in a press statement.
Icebergs have been tumbling down from the region’s glaciers for thousands of years as part of a natural cycle that usually balanced glacier growth in the winter with melting and retreating in the summer. But this new study finds that retreat has far outpaced growth throughout the 21st century. The ice reserve remained relatively steady from 1985 to 2000 but then there was a massive recession that continues to this day.
The research showed a glacier called Zachariae Isstrom lost the most ice. It dropped a whopping 160 billion metric tons of mass due to a retreat. This was followed by the Jakobshavn Isbrae on the western coast, which lost 88 billion metric tons. Qajuuttap Sermia was the only glacier that gained any ice but that was too small to offset the losses from other glaciers.
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First uploaded on: 19-01-2024 at 18:00 IST
