Study finds limit on evaporation to ice sheets, but that may change !

"Normally, the air temperature goes down as you climb, but near the surface in Greenland, it gets warmer," said David Noone, an Oregon State University professor who is an atmospheric scientist and principal investigator on the study. "The surface is very cold, but it can be as much as 20 degrees

warmer just 30 to 40 feet up in the air. It's enough that you can feel the difference between your nose and your toes."

"The temperature difference effectively forms a lid so that there is hardly any evaporation. Warm air likes to rise, but if it is already warmer up above the air is trapped nearer the ground. One consequence is that layers of fog form from water that had recently evaporated. Eventually the small fog water-drops drift back down to the very cold surface where it refreezes onto the ice sheet."

"It's a handy little trick of nature."

Max Berkelhammer, a researcher at the University of Illinois and lead author on the study, said scientists have been aware of "accumulation zones" in high-altitude areas of the ice sheet, but they haven't been comprehensively measured because of the difficulty in analyzing evaporation and condensation over time.

"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 Berkelhammer, who did his post-doctoral work with Noone when both were at the University of Colorado. "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 research aims to better understand how ice cores capture information about past temperatures in Greenland. The snow and ice on Greenland's interior originated from ocean water far to the south and is transported northward by weather systems and storms, and finally falls as snow on the pristine ice sheet.