The signs of Global Warming are turning up in all sorts of strange places, latest among them is the fact that Iceland is rising out of the seas as the glaciers that once held it down melt. Airlines may have reason to fear what follows.
The fact that landmasses ascend when warmer conditions remove the ice above them has been known for some time. Postglacial rebound can be seen at many locations that the last Ice Age buried deep, and Greenland may be accelerating.
Rebound is slow however, and it can be a challenge to distinguish whether rebound is the result of recent warming, or a delayed response to something that happened thousands of years ago.
This is what makes a study of Iceland published in Geophysical Research Letters interesting. The authors are confident that they can show the speed with which the island is rising can be attributed to recent effects.
"Our research makes the connection between recent accelerated uplift and the accelerated melting of the Icelandic ice caps," says lead author Kathleen Compton, a Ph.D. student at the University of Arizona.
Co-author Dr Richard Bennett, also of the University of Arizona adds, "Iceland is the first place we can say accelerated uplift means accelerated ice mass loss.”
Part of the reason the authors are so sure, is the sheer speed with which Iceland is rising. On a human scale 35mm, as the fastest parts of the island are moving, does not sound like much. It is around the speed at which fingernails grow and half the rate of horizontal movement of some continental plates. For vertical movement however, this is remarkable.
Compton and Bennett based their observations on 62 GPS receivers attached to rocks across Iceland, some of which Bennett installed himself. Of these 27 are accelerating noticeably. This allowed them to observe not only an average rate of uplift, but how different parts of the island compare, and how the speed has changed with time. This enabled the research team to connect the fastest growth with the retreat of glaciers, which in turn can be directly attributed to higher temperatures over the last 35 years. The changes are so great the team think further analysis may reveal seasonal patterns.
"What we're observing is a climatically induced change in Earth's surface," says Bennett. Mathematical modeling found that uplift this fast required not only substantial loss of ice, but for the melt to be speeding up. "There's no way to explain that accelerated uplift unless the glacier is disappearing at an accelerated rate."
The finding is primarily a symptom of global problems, rather than a cause. Nevertheless, Bennett also warns that the last time Iceland was moving rapidly in response to the look of glaciers there was an accompanying increase in volcanic activity, up to thirty times what is seen today. After the 2010 Eyjafjallajökull eruption shut down airline flights across Europe, such an upsurge could force a rethink of transportation across much of the northern hemisphere.
Credit: Giantrabbit via Shutterstock. Iceland's name is increasingly inaccurate.
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