Thousands of icebergs have already slipped into the sea from the Jakobshavn glacier in Greenland. One of them is said to have sunk the "Titanic" in 1912. The glacier is huge, almost seven percent of the entire Greenlandic ice flow over him - and faster than any other. For 20 years, the Jakobshavn Glacier has been shrinking at great speed, contributing to the rise in sea level.
But now there is a surprising U-turn, reports the American space agency Nasa. The glacier now flows slower and get thicker again, they said. Instead of retreating increasingly inland, he moved towards the sea. However, there is no such thing as an all-clear: According to the researchers, the ice of the Jakobshavn continues to increase the oceans - but not quite as much.
"In the beginning we could not believe it," says Ala Khazendar from NASA. "We actually assumed that things will continue as they have for the past 20 years."
In the long term, the glacier will shrink again
The scientists attribute the change on the glacier to a sea current in the Atlantic Ocean. They have cooled the water there in the past three years to temperatures that were last reached in the mid-eighties, write the researchers in the journal "Nature Geoscience"
The so-called North Atlantic Oscillation has set the cold water in motion. These are fluctuations in air pressure between Iceland and the Azores, which heat and cool the Atlantic about every 5 to 20 years. Such a reversal has just taken place and cooled the Atlantic as a whole.
Also, the water off Greenland's southwest coast has become considerably colder in 2016 and the west coast wandered up towards Jakobshavn glacier. Between 2013 and 2016, the water temperature near the glacier dropped by one degree.
However, the glacier is not saved. As soon as the North Atlantic Oscillation reverses again and the ocean warms, the ice is likely to shrink again. "In the long term, the ocean is warming up - and having such a huge impact on the glaciers is not a good sign for Greenland's ice sheet," says NASA researcher Josh Willis.
Glacier has been shrinking since the early nineties
For the study, the researchers had evaluated data on the water temperature around Greenland. To find out where the water came from, they tracked the flow in computer simulations for almost a thousand kilometers.
NASA has been watching the Jakobshavn Glacier for many years. She assumes that his rapid shrinking began in the early nineties. At that time, the ice shelf broke off, the part of the glacier that floats on the sea. This usually reduces the flow rate of a glacier. If the ice shelf is missing, the glacier flows much faster.
Thus, the Jakobshavn glacier also more and more ice into the sea, it was getting thinner - between 2003 and 2016 by 152 meters.