Iceland rises as its glaciers melt from climate change

January 29, 2015, University of Arizona
This global positioning satellite receiver is part of Iceland's network of 62 such receivers that geoscientists are using to detect movements of the Icelandic crust that are as small as one millimeter per year. Langjökull glacier can be seen in the background. Credit: Richard A. Bennett/ University of Arizona

The Earth's crust under Iceland is rebounding as global warming melts the island's great ice caps, a University of Arizona-led team reports in an upcoming issue of Geophysical Research Letters.

The paper is the first to show the current fast uplift of the Icelandic crust is a result of accelerated melting of the island's glaciers and coincides with the onset of warming that began about 30 years ago, the scientists said.

Some sites in south-central Iceland are moving upward as much as 1.4 inches (35 mm) per year - a speed that surprised the researchers.

"Our research makes the connection between recent accelerated uplift and the accelerated melting of the Icelandic ," said first author Kathleen Compton, a UA geosciences doctoral candidate.

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 has been an open question until now, said co-author Richard Bennett, a UA associate professor of geosciences.

"Iceland is the first place we can say accelerated uplift means accelerated ice mass loss," Bennett said.

To figure out how fast the crust was moving upward, the team used a network of 62 global positioning satellite receivers fastened to rocks throughout Iceland. By tracking the position of the GPS receivers year after year, the scientists "watch" the rocks move and can calculate how far they have traveled - a technique called geodesy.

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.

Iceland's glaciers (white) are melting faster and faster. As a result, the Icelandic crust near the glaciers is rebounding at an accelerated rate -- in some cases as much as 1.4 inches (35 mm) per year, found a University of Arizona-led team of geoscientists. The researchers used Iceland's geodesy network of sensitive GPS receivers (red triangles) to figure out how fast the land is rising. Credit: Kathleen Compton/University of Arizona

He added 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 such as the 2010 eruption of Eyjafjallajökull, which had negative economic consequences worldwide.

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.

Some of Iceland's GPS receivers have been in place since 1995. Bennett, Hreinsdóttir and colleagues had installed 20 GPS receivers in Iceland in 2006 and 2009, thus boosting the coverage of the nation's geodesy network. In central and southern Iceland, where five of the largest ice caps are located, the receivers are 18 miles (30 km) or less apart on average.

The team primarily used the geodesy network to track geological activity such as earthquakes and volcanic eruptions.

In 2013, Bennett noticed one of long-running stations in the center of the country was showing that site was rebounding at an accelerated rate. He wondered about it, so he and his colleagues checked the nearby stations to see if they had recorded the same changes.

"The striking answer was, yes, they all do," he said. "We wondered what in the world could be causing this?"

The team began systematically analyzing years of signals from the entire network and found the fastest uplift was the 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.

Bennett said, "There's no way to explain that accelerated uplift unless the glacier is disappearing at an accelerated rate."

Estimating ice loss is laborious and difficult, he said. "Our hope is we can use current GPS measurements of uplift to more easily quantify ice loss."

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

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13 comments

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dogbert
1.8 / 5 (15) Jan 29, 2015
Why the conclusion that ice loss is due to AGW.
What about the mama under Iceland?
dogbert
1.7 / 5 (11) Jan 29, 2015
greenonions,

Well Dogbert might have done well to have read the article. Here is a couple of clues.

Temperature records for Iceland, some of which go back to the 1800s, show temperatures increasing since 1980.

There's no way to explain that accelerated uplift unless the glacier is disappearing at an accelerated rate.


So what makes the loss of glacier ice due to AGW instead of the magma under Iceland?

I did read the article, by the way. The author simple decided that the loss of the ice was due to AGW without supporting that assertion in any way.

So, why don't you support your assertion?

Wonder if dogbert can supply any research that shows how the 'mama' under Iceland has caused accelerated warming and melting.


I cannot and I have not made the assertion that magma has caused the melting. I simply pointed out that the assumption that AGW causes it is unsupported and that there could be other reasons for Iceland to lose ice.
darksoul1900
1 / 5 (3) Jan 30, 2015
News headline: "Iceland about to rise up and float just like in Avatar"
Whydening Gyre
4.2 / 5 (5) Jan 30, 2015
Anybody know a good source for data on ice loss for Iceland?
(I just wanted to say that for some reason...)
dogbert
2.1 / 5 (7) Jan 30, 2015
greenonions,

Dogbert. If you are not asserting that magma has caused the melting - why did you bring the subject up?


I pointed out that the author of the article presumed that AGW was causing the loss of ice in Iceland without providing any documentation or even reasoning which would support that unfounded conclusion.

If I had simply stopped there, your next question would have been "What else could account for the ice loss?". So when I pointed out that the assertion of AGW causing the ice loss was not supported, I provided a possible alternative cause.

Science allows the examination of alternatives. What does not belong in a science dialog is assertions which are not supported.

I made no assertion that magma was causing the ice loss. I presented it as a possibility.

The article actually makes the unsupported assumption that the rising elevation is due to ice loss without eliminating the possibility that the elevation could be due to magma pressure.
Whydening Gyre
4.5 / 5 (11) Jan 30, 2015
The article actually makes the unsupported assumption that the rising elevation is due to ice loss without eliminating the possibility that the elevation could be due to magma pressure.

Unsupported is not exactly correct. The conducted research was done as support of their hypothesis.
Of COURSE there are alternative possibilities. Those are just not represented by this particular research project and thusly, this article.
Prob'ly a pretty good bet that someone IS looking at them, tho...
dogbert
2.1 / 5 (7) Jan 30, 2015
greenonions,

It is completely appropriate to note that assertions should be supported, not simply provided as the belief of the person making the assertion.

In the absence of support for assertion, it is certainly appropriate to point out that the assertion is not supported.

You troll when you support assertion over evidence, silence over discussion.

This is a place to discusses science. If that offends you, you should leave it.
shavera
4.4 / 5 (13) Jan 30, 2015
dogbert, I think the original comment from greenonions lays it out pretty well. Magma's been under Iceland for a long time... but only relatively recently has warming and glacier loss been strongly observed. In areas without as much geothermal heating we also observe ice loss, consistent with the observations in Iceland.

Therefore it is eminently reasonable to conclude that the factors driving ice loss elsewhere (human-caused warming) is also responsible for the warming of ice in Iceland. It's not the most wild of leaps of logic one could make.

Unless you want to claim that the geologic activity in Iceland is historically unprecedented, in which case you'll need to provide evidence to support such a claim.
ReduceGHGs
4.6 / 5 (9) Jan 30, 2015
Despite the fact that EVERY respected scientific institution that considered the issue concluded that we are warming the earth many Congressmen/women say that it isn't happening. They reject the reality and put our future generations at risk for the sake of their fossil fuel sponsors or some political agenda. We don't need law makers that aren't working in our best interests. They need to be confronted and replaced.
Please join the efforts.
ExhaustingHabitability(dot)org
Eddy Courant
1 / 5 (4) Jan 30, 2015
Sea level rise compensated.
Rute
3.3 / 5 (3) Jan 31, 2015
While I agree that the increase in air temperature is the triggering factor in the melting, I wonder if this could be a self-amplifying phenomenon. If the glacier melting leads to increased volcanic activity, it probably leads to soot raining down on glaciers, decreasing their albedo which would further accelerate the melting. That's my five cents.
Maggnus
3.7 / 5 (6) Jan 31, 2015
While I agree that the increase in air temperature is the triggering factor in the melting, I wonder if this could be a self-amplifying phenomenon. If the glacier melting leads to increased volcanic activity, it probably leads to soot raining down on glaciers, decreasing their albedo which would further accelerate the melting. That's my five cents.


There is actually some traction in this, at least in Antarctica. See here: http://www.nature...ity.htm.
animah
5 / 5 (5) Feb 01, 2015
I would think testing for magma as a source of heating and ice loss is trivially testable via:

- Increase in soil temperature
- Increase in magma activity, which given the masses involved would result in a very noticeable uptick in seismic activity.

And since the above 2 are not seen to be occurring...

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