Greenland rising

Southern Greenland scenery, near Nanortalik, where fjords and mountains dominate the landscape.

Antarctica beckons, and on the other end of the earth, the island or continent or whatever we’re calling Greenland these days is rising, literally, thanks to global warming and a process called isostasy:

(Link) — [T]he only explanation for the strange uplift is the rate of ice melt caused, in part, by global warming. The melting and the resulting rise in sea level is one of the hallmarks of global warming, which has force researchers to resort to using some novel methods to overcome different seasonal and regional signals that obstruct their ability to measure the effect of rising temperatures.

Isostatic balance refers to the equilibrium between a floating object and the medium it displaces. Remove a rider from her surfboard and the board floats higher in the water than before. The continents are a giant version of that surfboard, they may feel solid and immovable over the course of a single may-fly human life, but we ride on the backs of drifting igneous rafts floating in a deep global ocean of red-hot lava.

On Greenland and throughout much of the cryosphere, ice loss is threatening that delicate floating balance; the underlying surface rises as frozen overburden melts away. It’s not usually a rapid process, there are places in North America and Europe where the earthen surface is still rising in relief from the days of now vanished glaciers that once ruled the Pleistocene thousands of years ago. But this rise seems to be new. 

Greenland is earth’s proverbial canary in the coal mine, easily studied and yet remote, sensitive to small changes in climate, changes that could in theory add up and tip over as dramatically as similar predecessors did at the end of the last ice-age, only this time compressed into decades instead of millennia. That continental canary is tweeting an alarm loud and clear, it remains to be seen if we’re wise enough to listen.


  1. F says

    Yeah, isostatic rebound, what? If Greenland and northern Europe continue to rise, we may be able to keep those fjords even with the sea level rising as well. Because I’d hate to have to pine for them.

  2. roxchix says

    As romantic or evocative as you make it sound, there is no global lava ocean (for one thing, if the upper mantle was molten, it would be called magma, not lava).

    The plates are riding on a mostly-global layer of silly putty, or hot (not melted) wax, not lava, if you want a familiar analogy. Average melt fraction of the asthenosphere is between .25% and 1.25%m and at most, under the mid-ocean ridges where there is active decompression melting of the asthenosphere, you may get regions of 3% melt, to the best of our knowledge.

    Next to the mistaken notion that people have that the downgoing slabs melt in subduction zones, this is probably plate tectonics pet peeve #2 for geologists. there is no global layer of lava/magma under the tectonic plates!

  3. says

    That’s a good point, and I actually pondered being more accurate, so I’m somewhat imprssed with your perceptive critique. But in the end I figured something like ‘quasi-plasticized upper mantle conglomerate’ does not turn a phrase or elucidate the non geo major quite like “ocean of lava.” But in light of this, maybe next time I’ll be more precise Rox :)

  4. says

    I have wondered if the relief of pressure from the Arctic and Antarctic would result in seismic events. E.G. A rising Greenland might accelerate seafloor spreading in the Mid-Atlantic ridge and slow the westward movement of the North American plate. So more earthquakes and vulcanism in Iceland, fewer on the west coast of North America. Has anyone studied this?

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