Extensive measurements from space and the Greenland bedrock show that extensive changes are happening with the Greenland ice cap.
In 2003, 111 km3 of ice disappeared per year and ten years later this figure had almost quadrupled to 428 km3 per year. These are huge amounts—1 km3 of ice corresponds to a piece that measures 1x1x1 kilometres. 100 to 400 of these giant ice cubes have disappeared each year and become large amounts of sea water.
Previously, the ice cap melted most rapidly in the North-Western and South-Eastern parts of Greenland. Here, the melt of large glaciers accelerates when the sea and weather are affected by rising temperatures in Earth’s atmosphere. Now, however, an accelerating loss of ice can also be observed in South-West Greenland, where there are no glaciers.
“The changes we see in the melt pattern now are significant and surprising. In addition to the known areas of glacial melt in the North-Western and South-Eastern parts of Greenland, the ice in South-West Greenland is now also melting. This is surprising, and the melt water from this area will likely be a major contribution to the global rise in sea levels,” says DTU Space Professor Shfaqat Abbas Khan.
The study concludes that periods of heavy melting will be more frequent due to the increased temperature levels in the Arctic. The major changes will primarily take place in the South-Western part of Greenland.
Greenland ice cap reacting quickly to changes
The researchers’ work also shows how sensitive the ice cap is to changes in the atmosphere and sea, and thus also in the wind and weather systems.
From early 2003 to mid-2013, the ice melt accelerated every year. However, by mid-2013 the situation changed very suddenly. The acceleration subsided and the ice almost stopped melting for the next 12 to 18 months. Subsequently, the melt has once again accelerated.
“When climate changes affect the weather systems, changes occur on the ice cap surprisingly quickly. The melt can accelerate or subside in a matter of months when the air and the ocean heat up or cool down. So, as the temperature in the atmosphere now continues to rise, we will see an immediate melt increase,” says Shfaqat Abbas Khan.
Typically, it is the large Greenlandic glaciers that are melting. Among other things, this is due partly to increased temperatures in land and partly to increased volumes of warmer sea water that penetrate and accelerate the melt where the glaciers meet the sea. In Southwest Greenland, the melt is fuelled by warmer inland air streams.
Multiple effects play a role in the climate changes
Greenland and the Arctic are affected by a phenomenon called the North Atlantic Oscillation (NAO), which leads to changes in the climate from year to year due to variations in atmospheric pressure. When the general climate changes of increased temperatures coincide with periods where the NAO also leads to temperature increases, the melt is accelerated even further.
“The reason why we are seeing such massive melt in recent years is that temporary heating from the NAO coincides with the more stable global warming. 30 years ago, these two effects were not significant enough to accelerate melting. Around the year 2000, the ice cap reached a tipping point so that it is now melting much faster than the average melt rate from 1950 to 2000,” says Ohio State University Professor Michael Belvis, who is the main author of the new study.
(Morten Garly Andersen)