Iceland is, in fact, a land of ice. It is home to at least 269 glaciers, which occupy the equivalent of over 1.4 billion Olympic swimming pools. But those glaciers are melting, causing the land underneath to rise as the weight of the ice lifts. According to a new study published online in Geophysical Research Letters in February, Iceland is actually rising over 30mm per year in some places, and the rate of rise is accelerating.
These were the findings of a team of researchers led by Richard Bennett, associate professor from the University of Arizona in Tucson. They have been doing field research in Iceland since 2006 to better understand the relationship between warming temperatures, glacial melt and land rise. To track the rate of glacier melt and measure the positioning of the earth, the team collected data from 62 GPS receivers fastened to rocks in Iceland. Most of those GPS receivers were already in place, but the group added 20 new receivers of its own.
It is challenging to accurately measure the uplift response to modern ice loss because the signal can be complicated by the remnant responses to past glacial retreat. But it turns out Iceland is a favorable place for GPS-based study, because research suggests these remnant responses are minimal: the observed changes in land positioning correspond mostly to recent changes in ice mass.
Bennett and his team first learned that land rise was accelerating in 2013 after they examined one of the oldest GPS stations, located in central Iceland. When they checked other nearby stations, these also showed an accelerating rate of rebound. By analyzing the signals from the GPS network using statistical modeling, the team then found that it was the region between several ice caps that rebounded the fastest. They estimated that the largest uplift took place near the center of Iceland, between two ice caps called Vatnajökull and Hofsjökull, with rates of over 30mm each year.
The researchers also observed a remarkable increase in the rate of ice loss due to melting in the years since 1995, when some of the continuously operating GPS receivers were first placed in Iceland. Kathleen Compton, a geosciences doctoral candidate at the University of Arizona in Tucson, one of the researchers on the team, decided to use mathematical models to test whether the acceleration in crust uplift corresponded to static or accelerating rates of ice melting. Her models indicated that for land rise to accelerate, ice loss must also accelerate. She also found a correlation between rising temperatures in Iceland and land lift. Temperature records for Iceland show an increase in warming began in 1980.
The team plans to analyze land uplift data to uncover seasonal variations in growth and melting of ice caps, especially during winter snow season and summer. “Our hope is we can use current GPS measurements of uplift to more easily quantify ice loss,” said Bennett in an interview published on the American Geophysical Union’s website.
In related research, in a 2006 paper in the Journal of Geophysics Research, Aðalgeirsdóttir et al. found that glacier ice loss in Iceland dates back to at least 1995 and this trend should continue. Scientific models demonstrate that specific glaciers—Hofsjökull and southern Vatnajökull—are likely to shrink by half in the coming two centuries. Another paper by Compton et al., published in Geophysical Research Letters this February, indicates that if glacier melt continues to accelerate at current rates in Iceland, central Iceland will probably rise at a rate of 40mm per year over the next decade.
Recent findings by Schmidt et al., published in 2012 on Earth and Planetary Science Letters, further suggest that continued glacier retreat could bring about upward movement of the earth’s mantle—the layer between the crust and the core—which could result in more volcanic eruptions and increase the volume of volcanic rocks during eruptions.
The natural and social impacts of warming-induced ice loss in Iceland are likely to grow over time and are critical subjects for further research.
To read more about glacial retreat and earth uplift, check out this past story on Glacierhub.org.