Sunday, January 25, 2015

Greenland Ice: The warmer it gets the faster it melts

Space Daily via SPX: Melting of glacial ice will probably raise sea level around the globe, but how fast this melting will happen is uncertain. In the case of the Greenland Ice Sheet, the more temperatures increase, the faster the ice will melt, according to computer model experiments by Penn State geoscientists.

"Although lots of people have thought about sea level rise from the ice sheets, we don't really know how fast that will happen," said Patrick Applegate, research associate, Penn State's Earth and Environmental Systems Institute.

If all the ice in the Greenland Ice Sheet melts, global sea level would rise by about 24 feet. In the last 100 years, sea level in the New York City area has only increased by about one foot. However, storm surges from hurricanes stack on top of this long-term increase, so sea level rise will allow future hurricanes to flood places where people are not ready for or used to flooding. A vivid example occurred during Hurricane Sandy when parts of the New York City subway tunnel system flooded.

Greenland might be especially vulnerable to melting because that area of the Earth sees about 50 percent more warming than the global average. Arctic sea ice, when it exists, reflects the sun's energy back through the atmosphere, but when the sea ice melts and there is open water, the water absorbs the sun's energy and reradiates it back into the air as heat.

Arctic sea ice coverage has decreased over the last few decades, and that decrease will probably continue in the future, leading to accelerated temperature rise over Greenland. Floating ice does not add to sea level, but the Greenland Ice Sheet rests on bedrock that is above sea level.

Feedbacks in the climate system cause accelerated temperature rise over the Arctic. Other feedbacks in the Greenland Ice Sheet that contribute to melting include height-melting feedback. A warm year in Greenland causes more melt around the edges of the ice sheet, lowering the surface. The atmosphere is warmer at lower altitudes, so the now lower surface experiences even more melting. This process can lead to accelerated ice melt and sea level rise....

A glacier seen from offshore near Amassalik, Greenland, shot by Christine Zenino Christine Zenino ,Wikimedia Commons via Flickr, under the Creative Commons Attribution 2.0 Generic license

No comments: