Researchers have found a layer of air near the surface of the ice sheet that is trapping moisture and reducing both evaportion and precipitation and limiting the melting of a large part of Greenland ice sheet.
Although Greenland ice sheet is melting rapidly in coastal areas, there is still some good news. Researchers have found that a large part of the ice sheet (40 percent) has been stable and rarely melting on the surface. Though, there is a possibility that the stability may not last long. A team of international researchers drew the conclusion after directly measuring the amount of precipitation on ice sheet.
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A warmer climate usually results in more precipitation, but scientists found no evidence of increased snowfall in the region, meaning that the surface is not losing much of its ice.
Researchers attribute this less melting of ice to a layer that was formed in the winters. The layer of air works as an insulator. It traps the moisture freed from the ice sheet and brings it back to the surface where it freezes again. In this way, it reduces both evaporation and precipitation.
Over the last 10 years, temperature has risen but not the precipitation over the central parts of Greenland ice sheet. That’s the mystery which they wanted to solve.
“We decided to investigate whether we could find the answer in the atmosphere above the ice sheet by measuring the atmospheric processes directly. We therefore took measurements of the water vapor in the atmosphere for three years.” Co researcher Hans Christian Steen-Larsen from University of Copenhagen said.
Researchers measured the water vapor in the atmosphere up to a height of 40 meters above the surface of the ice sheet because isotope ratio in water vapors can reveal something about their origin and fate.
It turned out that a unique weather system is prevailing in the atmosphere over the ice sheet during the winters. Closer to the surface it was very cold and about 100 meters up, air was more dynamic and warmer.
“By measuring the isotopic composition of the water vapor, we discovered that there was a clear distinction between the water vapor that was associated with the ice and the water vapor that was blown in higher up in the atmosphere,” explained Hans Christian Steen-Larsen. “There was a boundary layer that separated the two layers in the atmosphere. We were thus able to see a direct disconnection between the surface of the ice and the atmosphere above it – it would not have been possible to discover this if we had only looked at the water vapor amount in the air.”
The discovery of this new phenomenon explains why there is less than expected precipitation in the region and also why there is no relationship between temperature and precipitation on the Greenland ice sheet.
“Instruments capable of doing this are pretty new and while they have been used before on the ice sheet, they have never been able to run during an entire winter,” said lead researcher Max Berkelhammer from University of Illinois.
“I think at this point we are still the only group who has been able to run this type of instrument for an entire year on top of an ice sheet.”
The findings can help researchers to get an idea about how much precipitation fall and how much evaporated in the past but they are struggling to find what the situation will be like over hundreds of years in the future.
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Co-author of the study David Noone from Oregon State University says. “The fate of the ice sheet is in balance. It becomes a question of which influence is stronger.”