The notion that rock rebounds is not a new one, Sigrun Hreinsdottir, one of the principal investigators on the project, explained to The Washington Post. Land in Canada and Scandinavia is still slowly rising after being pushed down by glaciers during the last ice age. More recently, there are indications parts of Alaska and Chile are also experiencing a “rebound” phenomenon as glaciers retreat. But if those rocks are like a memory foam mattress, remaining compressed long after the pressure on them is gone, the rising land in Iceland is like a trampoline, springing back at a rate of nearly 1.4 inches per year.
“Iceland’s crust is showing the current response,” Hreinsdottir said. “It’s hard to find a more ideal place to study this.”
Hreinsdottir and her colleagues identified this change by examining 20 years of GPS data from more than five dozen points around the country. The height changes they identified, which are concentrated in central Iceland, correlate almost perfectly with the loss of ice documented by glaciologists, Hreinsdottir said. As Iceland’s glaciers continue to melt — the island loses about 11 billion tons of ice per year — the already-rapid rebounding process will accelerate. Relieved of their frozen burden, parts of the country could rise as fast as 1.6 inches per year by 2025 — growing at nearly the same rate as an elementary schooler.
This height change isn’t noticeable to the average human observer, but its consequences will be. Iceland sits atop one of the world’s most active volcanic hot spots, roiling with molten magma. The pressure reductions caused by the melting glaciers and rising land could create conditions that would cause mantle rocks to melt, further feeding Iceland’s already well-supplied volcanoes. Bárðarbunga, a volcano in the center of the island, has been spewing lava uninterrupted since August.
Hreinsdottir said the geological record from the end of the last ice age indicates Iceland saw an increase in volcanic activity after glaciers retreated. And the past five years have been packed with “interesting volcanic activity,” including Bárðarbunga and the 2010 eruption of Eyjafjallajökull, which is reported to have cost the global economy $5 billion.
“You can’t make any statistics from those few data points of course, but you do notice there might be a connection with the uplift,” Hreinsdottir said. “And our data does indicate that might be exactly what’s happening.”