The drum beat of climate change goes on and on but the tempo increases day by day

16 05 2015

One more post by Mark Cochrane…..

Mark Cochrane

Mark Cochrane

This Antarctic ice shelf could collapse by 2020, NASA says

It has been a really bad week for the ice shelves of the quickly warming Antarctic peninsula, the part of the vast Researchers Worried About Largest Ice Shelf In Antarctica : SCIENCE ...frozen continent that extends northward toward South America.

Earlier this week, we learned that the gigantic marine-based Larsen C ice shelf, which is almost as big as Scotland, has several worrisome vulnerabilities — including a growing rift across it. Scientists from the British Antarctic Survey and several other research centres say this could pose an “imminent risk” to its stability.

And now, NASA scientists are giving an even worse verdict for the remnants of the nearby Larsen B ice shelf, much of which already disintegrated back in 2002. Back then, the shelf lost a region larger than Rhode Island, but there are still 618 square miles left of it — for now.

Now collapsing  ice shelves themselves pose no risk for rising sea levels because they are already floating but it is the function that they provide which we are losing. These massive ice shelves act as ice dams that hold back the landbound ice on the Antarctic continent. They are the stoppers in the bottles of large glacier ice rivers that will more quickly drain into the seas once the shelves are gone. The speed up of drainage into the sea has already begun with the Leppard and Flask glaciers, pent up behind the remnants of the Larsen B ice shelf, dropping by 49 and 65 feet in elevation (15m and 20m), respectively, during the last decade, as they drain into the sea. Glacial ice melting does accelerate sea level rise. Now the Larsen C ice shelf is breaking up, likely freeing up much of the rest of the Antarctic Peninsula’s glaciers in the near future.

The ice on the ice on the Antarctic Peninsula is small potatoes compared to the rest of the continent but not for us, just another 0.45m (1.5 ft) potential sea level rise. Ignoring the Antarctic continent and Greenland, the peninsula’s glaciers are the equivalent to

the potential contribution of all of the world’s other glaciers and ice caps, combined.

Recall, that just last year we learned that the West Antarctic ice sheet collapse is now foreordained. We cannot stop it even if we tried, we can only speed up or slow the inevitable. That brings with it another 3-5m of sea level rise. There is similar news about the mother load of ice on East Antarctica (link) coming unglued, with another 5m of sea level rise on the fast track (of 70m total), but I am still dubious that this is imminent, as of yet. Then there is Greenland with, potentially another 7m sea level worth of ice, and a mass loss rate that is 155% of that from Antarctica.

The most recent IPCC (AR5) projections of sea level rise call for between 22 and 82cm of sea level rise by the end of the century. If you have to bet though on whether reality will come in at over or under that range, I know which way I am betting. Incidentally, these scientists have projected a maximum possibility of 1.9m of sea level rise by 2100, but with only a 5% chance of being over 1.8m (link). One thing that is for certain, the rate at which sea level is rising will still be accelerating throughout the century. Sea level rise will not stop in 2100, it will just be getting warmed up, so to speak. With 10% of the global population living below 10m elevation above sea level, this is going to lead to immense amounts of landward migration in coming decades and centuries. It is not a question of homes going under the waves, it is one of how often they will be going under storm surges in the coming years. A little sea level rise goes a long way in terms of global disruption…




3 responses

17 05 2015

Good write-up, the “stopper” function of ice shelves was an interesting point.

I thought Dave Cohen’s latest post tied in nicely on the subject of this post – indeed the drum beat of Flatland also goes on and on…

17 05 2015

What a great website….. thanks for the heads up!

20 05 2015
Anthony William O'brien

Got to agree with the living in la la land.

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