Greenland ice sheet has been melting faster than ever before. It is well known that changes in water temperature, precipitation, and air temperature influence melting events. Now a group of researchers has found that cloudy skies accelerate the ice sheet melting by one-third, compared with clear skies. Findings of the study conducted by Kristof Van Tricht of the University of Leuven, Belgium were published Tuesday in Nature Communications.
Clouds play a much bigger role in accelerating the melt
Van Tricht and his colleagues found that clouds play a much bigger role in accelerating the melt than previously thought. It is the first time the role of clouds in Greenland ice sheet melting has been calculated. Researchers used satellite data to monitor cloud cover over the Greenland between 2007 and 2010. Then they compared results with ground-based observations.
Clouds help add mass to the ice sheet when it snows. They block sunlight that lowers the temperatures. But they also act as a blanket that keeps the surface warm, especially at night. The impact is not clearly visible during the daytime melting, but it leaves a huge impact during the following night. A large amount of meltwater is held in the upper levels of the snowpack. Under clear skies, much of the meltwater refreezes as the surface gets colder.
Greenland losing an extra 56 billion tons of meltwater
During a cloudy night, the surface is relatively warmer, preventing much of the meltwater from refreezing. As a result, excess meltwater drains into the ocean. Researchers estimate that it results in an extra 56 billion tons of meltwater reaching the ocean every year, compared to a scenario without clouds. Findings of the study will become more important in the future because several climate models predict that cloud cover will rise significantly as atmospheric temperatures rise and oceanic evaporation increases.
Van Tricht said adding cloud cover to existing climate models will further improve their predictive value and accuracy. The alarming pace of Greenland ice sheet melting is predicted to increase sea levels and disrupt the thermohaline currents that distribute heat and nutrients across the globe through gradients.