Global sea levels will continue to rise in the 21st century. But Greenland, one of the main sources of this growth, will see the opposite effect.
The cause is the reaction of the earth's surface to the loss of a huge mass of ice. The Greenland ice sheet, whose area is about three times larger than the Moscow region and reaches a thickness of more than three kilometers, has been pressing on the earth's crust for decades. Now that the ice is gone, the land is starting to rise and relative sea levels are falling.
Land gain in Greenland is ahead of all forecasts
This process is called ice isostatic compensation. It has long been thought that on human time scales, only the upper part of the Earth's crust reacts, while the mantle below it moves extremely slowly – over thousands of years. However, GPS satellite measurements show that Greenland's surface is rising much faster.
The authors of a new study published on NatureLed by Lauren Lewwright of Columbia University, concluded that the coating can “flow” faster if the load is suddenly removed. Including this accelerated motion in the models has yielded an unexpected result: by 2100, sea levels off Greenland could fall by 1-4 meters, 30-65% higher than previous estimates.
“The speed of reaction depends on the speed of the load. If you suddenly jump off the bridge, the consequences will be severe,” explains geophysicist Roger Creel, who was not involved in the work.
Gravity also plays a role
There is an additional factor. The mass of the iceberg itself attracts seawater. As it melts, this attraction weakens and the water is redistributed to other areas of the planet. As a result, global sea levels are rising and sea levels off the coast of Greenland are falling.
The Intergovernmental Panel on Climate Change previously suggested a similar impact but considered it moderate. New data force us to reconsider these estimates.
Historical clues and future risks
The study also relied on geological evidence from the past. The climate cooling traces of the Little Ice Age show that ice volume and sea level in the region changed quite rapidly. This increases confidence in the new calculations, says geophysicist Natalia Gomez from McGill University.
For Greenland itself, the consequences will be dire. Rising sea floors will expose rocks in ports and shipping channels, making navigation more difficult. Coastal ecosystems – mussels, algae, crustaceans – could run out of water. Fisheries and logistics will be affected.
For other countries, the effect will also be unpleasant. The melting of the Greenland ice sheet will accelerate sea level rise in remote regions from the North Atlantic to the tropics. Low-lying coasts in Europe, North America and island nations will face increased erosion, increased flooding and coastal salinization, putting pressure on cities, agriculture and water supplies.
“The difference between whether you can sail from a port or whether you have to build a new port is huge,” Creel emphasized.
It's all about emissions
The scale of the changes depends on future CO₂ emissions. If current trends continue, sea levels at rapidly melting glaciers such as Helheim could fall by nearly 3.8 meters by the end of the century. If warming is limited to 2°C, the depth will be about half a meter.
While in some coastal areas, sea levels are still rising. However, according to calculations, this is only temporary. In some places, changes are already clearly visible. Fisherman Leif Fontein from Sisimiut said the coastline in one of the fjords has expanded significantly in recent years.
“This can be seen with the naked eye; you don't even need to measure,” he notes.
The main question now, he said, is not whether change will happen but how to adapt to it.
