Researchers Use GPS to Measure Ice Loss in Greenland

Ohio State University researchers have come up with a novel method of using GPS for measuring temporary alterations in the rate of ice loss in Greenland. In addition, a link has been found to exist between the ice and the atmosphere over it.

Published in the Proceedings of the National Academy of Sciences’ early online edition, the study reveals the detection capabilities of GPS to trace several impacts like uplift of bedrock, ice loss, rise in sea level and changes in air pressure, resulting from climate change.

The research team informed that ice flowed rapidly into the sea due to high temperature in 2010. In fact, about 100 billion tons of ice has melted away from the continent within a period of 6 months.

Based on the pressure created by weight atop, the earth compresses or expands and measurements can be made with Greenland bedrock that acts as a scale. The accumulation of ice will push the bedrock downward, while melting of ice elevates the bedrock. Greenland has been evaluated to have sunk by 6 mm during 2010 winter. High air pressure atop the ice caused 3 mm of the sinking, while ice accumulation led to another 3 mm of sinking. Bedrock was found to elevate 11 mm during summer. It however relapsed owing to ice loss.

The network of GPS stations have been positioned across the Greenland ice sheet, in addition to mounting 50 transmitters closely. GPS antennas were installed on poles fastened within bare rock. This versatile network is called the Greenland GPS Network (GNET).

The detailed measurements from GNET enabled the researchers to separate the air pressure signal from the bedrock’s overall motion.

The bedrock’s "bathroom scale" movement shows reaction with respect to weight of the air and the weight of the ice.

GNET measurements were compared to eight year- period of air pressure data to analyze the patterns in the fall and rise of the bedrock.

There is increase in air pressure during the spring while it decreases during summer and fall. In contrast, the weight of the ice rises in spring, rapidly decreases in summer, and again starts to recover during fall.

Based on the interchange in these two cycles, a seasonal cycle is seen in bedrock displacement.

Air pressure signal measurements will lead to ice mass evaluation. GNET can be optimized as an 'ice-weighing machine' by comparing the displacements of the GPS stations on a day-to-day basis with alterations in surface pressure fields generated by numerical weather models.