Bedrock rises as ice melts in Greenland
Greenland is becoming greener again, a new international study shows. The year 2010 was hot, triggering accelerated ice loss in southern Greenland by 100 billion tonnes. The study results also reveal how large portions of the island's bedrock rock rose another quarter of an inch during this period. Ice weighs down bedrock, but the rocky coast rises as the ice melts away. Scientists from Denmark, Luxembourg and the United States measured the natural response of the island's bedrock to the shrinking weight of ice above it. They used a network of almost 50 global positioning systems (GPSs) located across the coast of Greenland to get the data they needed for the Greenland GPS Network (GNET) project. Leading the project, Professor Michael Bevis from the School of Earth Sciences at Ohio State University in the United States said the Greenland Ice Sheet melts year after year, something that in turn allows the island's bedrock to emerge even more. According to the scientists, a number of the Greenland-based GPS stations detect a rise of 15 mm or more in the rocky coast each year. However, last year's rise in temperature raised the bedrock as high as 20 mm at several sites. Speaking to an audience at the recent American Geophysical Union meeting in San Francisco, Professor Bevis said: 'Pulses of extra melting and uplift imply that we'll experience pulses of extra sea level rise. The process is not really a steady process.' Professor Bevis and colleagues took advantage of the natural flexure of the island's bedrock to measure the weight of the ice sheet. He went on to say that the anomalous uplift that GNET detected in 2010 was brought on by the phenomenon of anomalous ice loss during that year. An 'anomaly' represents the number of extra melting days. 'Really, there is no other explanation,' Professor Bevis said. 'The uplift anomaly correlates with maps of the 2010 melting day anomaly. In locations where there were many extra days of melting in 2010, the uplift anomaly is highest.' The measurements helped the team determine that as the ice melted away, the rocky coast emerged even higher. The researchers said the amount of uplift varied between every station, due to the proximity of each GPS station to areas where ice loss was greatest. The data showed that southern Greenland stations located very close to zones of heavy ice loss increased by as much as 20 mm over a 5-month period. Stations situated far away rose at least 5 mm during the course of the 2010 melting season. It should be noted that stations located in northern Greenland hardly moved at all. GNET installed GPS stations in the bedrock from 2007 to 2009, specifically in the rocky coast around the ice sheet margins. According to the scientists, GNET and related GPS networks across the globe can give researchers the means to measure ice loss after the Gravity Recovery and Climate Experiment (GRACE) satellites are retired in 2015. Researchers from the Danish Technical University in Copenhagen, the Space Institute in Denmark, the University of Luxembourg and the University of Colorado contributed to this study.For more information, please visit: GNET:http://www.polenet.org/projects/GNET/index.phpOhio State University:http://www.osu.edu/
Countries
Denmark, Luxembourg, United States