From the “Antarctic ice is normal now but just you wait” department….
Above: most recent data from NSIDC.
….and the UNIVERSITY OF EDINBURGH:
Antarctica’s past shows region’s vulnerability to climate change
Fresh understanding of West Antarctica has revealed how the region’s ice sheet could become unstable in a warming world.
Scientists studying the region’s landscape have determined how it reacted to a period of warming after the coldest point of the most recent Ice Age, some 21,000 years ago.
As the Earth warmed, the West Antarctic Ice Sheet reached a tipping point after which it thinned relatively quickly, losing 400m of thickness in 3,000 years, researchers found. This caused sea levels around the world to increase by up to two metres.
Their findings will help scientists understand how the region may behave under future environmental change.
Researchers studied peaks protruding through ice in the Ellsworth Mountains on the Atlantic coast of the continent, to determine how the land’s ice coverage has changed since the Ice Age.
Scientists used chemical technology – known as exposure dating – to calculate how long rocks on the mountainside had been free from ice cover. They used their results to determine how the height of the ice sheet had changed over thousands of years.
They found that this sector of the ice sheet – close to the Weddell Sea – had remained covered with thick ice long after other parts of the Earth had begun to emerge from the Ice Age. Heavier snowfall, caused by warmer air, probably helped to maintain the ice thickness.
As the seas warmed, ice at the coast began to be lost to the oceans. Eventually, a tipping point was reached after which the ice sheet thinned more rapidly, retreating inland.
The study, carried out in collaboration with Northumbria University, Newcastle University and the Scottish Universities Environmental Research Centre, was published in Nature Communications. It was supported by the Natural Environment Research Council.
Dr Andrew Hein of the University of Edinburgh’s School of GeoSciences, who jointly led the study, said: “West Antarctica has undergone complex changes since the last Ice Age, and it quickly became unstable – similar processes may dominate the future of the region in a warmer world.”
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Just clarify, are we talking about cold ice, which results from Ice Ages and the like, or warm ice, which (like warm snow) results from Man Made Global Warming?
I don’t think it is possible for us to go for six months without some article about some ice shelf melting or threatening to break away in the Antarctic getting into the regular media. It all gets to be very redundant and hard for even those of us interested to not begin to see it as more blah blah blah. If something really big having global implications did happen it would be hard for them to get the attention of the layman because of their constant cries of wolf over the last decades. The average person would see the news and think ‘Same S%!t different day. So what’s new?’ And to be quite frank that is exactly my reaction to this article.
The “rapid” melting back then caused 2m sea level rise in 3,000 years. Yikes! so fast! we are going to drown! Oh….3,000 years…never mind…
Has there ever been a paper showing an unconformity in Antarctic ice layers shown in drill cores? If ice is lost from the land based portion, an unconformity is a plausible first signal. BTW it would play hell with chronologies.
If no unconformity has been found, there is no point in hypotheses about ice loss from melting.
Geoff
Ice doesn’t melt in Antarctica. It calves into the sea or sublimates.
In Greenland “unconformities” (melt layers) occasionally occur, especially in the south. In Antarctica they are absent or extremely rare.They certainly never occur up near the ice-divides where ice-cores are drilled.
The lowered level of the glacier in this case was entirely due to increased calving (marine draw-down).
Ice in Antarctica does sublimate, i e turn directly from ice to water vapor. This paper is based on dating “blue-ice moraines” left by such sublimation.
PS
Perhaps I should have mentioned that melting does occur in some areas at the bottom of the ice-sheet by geothermal heat. That is the reason that there are lakes under the ice in some areas.
TTY,
Thank you. All that you commented has been known for a long time.
This is what I am getting at. If Antarctic ice is going to contribute to ocean level rise where does the added water come from?
For ice above land, sublimation is one way. Has it been measured accurately? Another way is basal meltwater, but it is hardly related to CO2. Another path is the toothpaste method, squeezing ice into the sea, but it’s importance is limited to the relatively small area of glaciers.
Of course, melting of ice now floating on water does not much affect levels, Avogadro.
When there are several theoretical ways for ocean levels to be affected, often one or two might dominate. Which are the major postulated players and how well are they quantified?
Yes, I am aware of glaciers on bedrock in shallow water and some of their complications.
Geoff
Geoff Sherrington on August 23, 2016 at 4:41 pm
TTY,
Thank you. All that you commented has been known for a long time.
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Yep, but – wrong adress. Please tell that Obama, Merkel and IPCC.
They should know too.
BS!
Chicken Little is alive and well.