UA research team shows climate's influence on geology

Published: Jan. 30, 2015 at 5:50 PM MST|Updated: Feb. 13, 2015 at 5:50 PM MST
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TUCSON, AZ (Tucson News Now) - Climate change has a direct influence on the Earth's crust under Iceland, which is experiencing dramatic uplift as glaciers melt, according to research done by a University of Arizona-led team.

A paper to be published in an upcoming issue of Geophysical Research Letters is the first to show that the accelerating melting of Iceland's glaciers and uplifting of the Icelandic crust coincides with warming that began about 30 years ago.

"Our research makes the connection between recent accelerated uplift and the accelerated melting of the Icelandic ice caps," first author Kathleen Compton, a UA geosciences doctoral candidate, said in a press release from the university.

Some sites in south-central Iceland are moving upward as much as 1.4 inches per year - a speed that surprised the researchers.

Geologists have long known that as glaciers melt and become lighter, the Earth rebounds as the weight of the ice decreases.

Whether the current rebound geologists detect is related to past deglaciation or modern ice loss has been an open question until now, said co-author Richard Bennett, a UA associate professor of geosciences.

The team used satellite geodesy to track the position of rock-mounted GPS receivers throughout Iceland to figure out how fast the crust was rising.

The new work shows that, at least for Iceland, the land's current accelerating uplift is directly related to the thinning of glaciers and to global warming.

"What we're observing is a climatically induced change in the Earth's surface," Bennett said.

Deglaciation could also mean an increase in volcanic activity.

Bennett said there is geological evidence that during the past deglaciation roughly 12,000 years ago, volcanic activity in some regions of Iceland increased thirtyfold.

Others have estimated the Icelandic crust's rebound from warming-induced ice loss could increase the frequency of volcanic eruptions.

The article "Climate driven vertical acceleration of Icelandic crust measured by CGPS geodesy" by Compton, Bennett and their co-author Sigrun Hreinsdóttir of GNS Science in Avalon, New Zealand, was accepted for publication Jan. 14, 2015, and is soon to be published online. The National Science Foundation and the Icelandic Center for Research funded the research.

In 2013, Bennett noticed one of the long-running stations in the center of the country was showing that site was rebounding at an accelerated rate.

The team found the fastest uplift was a region between several large ice caps. The rate of uplift slowed the farther the receiver was from the ice cap region.

Other researchers had been measuring ice loss and observed a notable uptick in the rate of melting since 1995. Temperature records for Iceland, some of which go back to the 1800s, show temperatures increasing since 1980.

To determine whether the same rate of ice loss year after year could cause such an acceleration in uplift, Compton tested that idea using mathematical models. The answer was no: The glaciers had to be melting faster and faster every year to be causing more and more uplift.

Compton found the onset of rising temperatures and the loss of ice corresponded tightly with her estimates of when uplift began.

"I was surprised how well everything lined up," she said.

The team's next step is to analyze the uplift data to reveal the seasonal variation as the ice caps grow during the winter snow season and melt during the summer.

Copyright 2015 Tucson News Now. All rights reserved. The University of Arizona contributed to this report.