Wyrd - OE: that which has become; fate-shaping; destiny-unfolding

Sunday, 2 June 2013

From White to Green - Greenland's Glaciers are History

Article first published as From White to Green - Greenland's Glaciers are History on Technorati.

Greenland ice sheets (Credit: destination arctic circle/ Flickr)
Take a long hard look at Greenland's towering glacial caps - they may well already be history. That's according to a paper published in Nature Climate Change. Scientists have already noticed that the speed at which Greenland's glaciers are rushing into the sea has accelerated. And they have long-feared that, without commitments to curb our greenhouse gas emissions, much of its ice cap will eventually disappear into the sea.

But there is now research to suggest the threshold has already been passed. Previous models made some fairly simple assumptions about how the 2 mile-thick ice block, which is plastered over much of Greenland, will melt. And they gave some hope that the worst of the melting could still be avoided, if we were to pull the plug on our emissions.

Fade to green?

With this new research, however, the physics of Greenland's ice-melting process have been painted out in finer detail. And if the authors are right, the amount of global warming we have stored up, from our emissions so far, may be enough to transform Greenland. The world's biggest island could shift from an icy whiteness to a truly green land.

Ice sheet thickness (km) today (E1) and projected in future (E2/3)
The reason for the change in outlook? The simple realization that as the 2-mile high icy plateaus melt they get considerably lower. And the lower the ice surface, the warmer the air above them gets, pushing the pace of melt even faster – a positive feedback.

Positive feedbacks are the 'loaded dice' of the game of climate crap-shoot we're playing. They push the odds in favor of dangerous consequences, by accelerating the rates of change kicked off by global warming. But how dangerous would it be, if Greenland were to disgorge its entire ice sheet into the oceans, as this study suggests?

2-miles of ice, 21-feet of water

Well, how about seas lapping 21-feet higher than they do now? It's fairly obvious that this level of sea-rise would be immensely disruptive; fortunately it is likely to be immensely slow, too. The study showed that Greenland would lose its signature ice-sheets over tens of thousands of years. But the fact is that this research adds another ratchet upwards to the sea-level rises expected by the end of the century.

Even small sea-level rises will bring many more coastal-dwellers within reach of the sea's awesome natural power. Hurricane surges, tidal waves, tsunamis – they will all get an unwelcome destructive boost, as Greenland nudges up its contribution. More than enough to worry about, then. But of course models are just models, not reality. Ice-sheet models are no different. They will be debated and revised, and maybe things will look better, as climate science progresses.

Or maybe worse. And that's the nub of the matter. Climate scientists have been pointing out the potential rocks that could hole the good ship humanity for some time now. They're difficult to spot – things are often a little misty – but the warnings are clear. If we keep on our reckless journey, into climate change's unknown rapids, sooner or later we're going to hit one of those rocks – and sink.

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