How Fast Is Greenland Melting?
The Greenland ice cap is over 2km thick, made of (a mind-blowing) 2,850,000km³ of ice, which is melting faster and faster. Once it has completely melted, global sea levels will rise by 7.2m. How much time have we got?
If future emissions are very high, [the melt rate] could rise to up to 35,900bn tonnes per century.
That sounds like a lot. But is it?
35,900bn tonnes of ice will melt into about 35,900km³ of water in the ocean. That's 1.25% of the total Greenland ice cap. That would lead to a sea level rise of about 9cm. In a century.
Suppose we really roast the planet and it's five times worse than the top-end estimate in this paper. Over the next century 6.25% of the Greenland ice cap would melt, leading to 45cm of sea level rise.
This would be bad, but it's probably not the most dangerous consequence of climate change. See Are We All Going To Die?
Note: there are various unpredictable scenarios that might significantly alter the rate at which Greenland melts, including:
- Great chunks of the Greenland ice sheet might start slipping faster into the sea.
- Disruption to the jet stream might lead to lots of warm rain falling on Greenland, melting it faster.
- Disruption to the jet stream might lead to lots of cold snow falling on Greenland, reversing the net loss of ice.
- Pools/lakes of melt water forming on the Greenland ice surface will absorb more sunlight than ice and lead to faster melting.
Long-Term Bad News
As the Greenland ice sheet melts, it loses altitude, is exposed to warmer air and melts faster! This is an example of run-away positive feedback.
The only ways to stop this are global-scale geo-engineering to make the world colder than we found it - inherently very risky - or to find a way fast to make it snow a lot, lot more on Greenland.
In coming centuries, London can be protected using a 7m seawall but the Embankment will look very different. Sadly, the same thing is happening in Antarctica which, if it melts, will contribute another 60m sea-level rise.
Watch Greenland Melting
In Frozen Planet II: Episocde 6 Our Frozen Planet (at 5m30s) we see lakes of melt water on the ice surface, we are told about their increasing number, and incredibly we see a decent-sized river flowing on top of a glacier.
Thank you to Alex Zeffertt for his suggestion.
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