There is a new paper out in Nature Communications about meltwater pulses and accelerated ice loss from Antarctica. It describes model simulations of Antarctic ice sheet evolution over the last 25,000 years. What was found was "several episodes of accelerated ice-sheet recession, the largest being coincident with meltwater pulse 1A." The abstract continues: "This resulted from reduced Southern Ocean overturning following Heinrich Event 1, when warmer subsurface water thermally eroded grounded marine-based ice and instigated a positive feedback that further accelerated ice-sheet retreat."
Below is a clever animation from the Nature Communications article, demonstrating how the warmer sub-surface of the ocean can melt Antarctica.
Click the squares in the bottom right hand corner to view full screen.
There is a press release on the website of the Australian Research Council's Centre of Excellence for Climate System Science. It begins with:
Current changes in the ocean around Antarctica are disturbingly close to conditions 14,000 years ago that new research shows may have led to the rapid melting of Antarctic ice and an abrupt 3-4 metre rise in global sea level.
The research published in Nature Communications found that in the past, when ocean temperatures around Antarctica became more layered - with a warm layer of water below a cold surface layer - ice sheets and glaciers melted much faster than when the cool and warm layers mixed more easily.
This defined layering of temperatures is exactly what is happening now around the Antarctic.
The modelling shows the last time this occurred, 14,000 years ago, the Antarctic alone contributed 3-4 metres to global sea levels in just a few centuries.
The press release also has a comment on the related observed increase in sea ice around Antarctica:
The accelerating melting of land ice into the sea makes the surface of the ocean around Antarctica colder, less salty and more easily frozen, leading to extensive sea ice in some areas. It is one of the reasons ascribed to the increasing trend in sea ice around Antarctica.
Anthony Watts claims...erm what?
Anthony Watts derides the science as is usual. He thinks he's being an awfully clever little denier when he writes:
While we have record high sea ice in Antarctica, the Australian research council is figuring that a collapse of Antarctic ice is imminent, followed by 3-4 meters of sea-level rise. It’s all based on a model that they took back in time to 14,000 years ago to model “meltwater pulse 1A” seen in the graph below. The only problem is, we aren’t coming out of an ice age.
Does Anthony think there is no ice on continental Antarctica? Seriously? And yet he comments about the record high sea ice, which the press release discussed. Perhaps he thinks that the sea ice is around a tropical island continent. Or maybe he thinks that a hotter world means ice stops melting. Not yet, Anthony. When it's all gone then it will stop melting and we'll stop "coming out of an ice age".
Some more reading
There was a paper in Nature on a similar subject by Eelco J. Rohling et al back in 2004, which you might like to read. It's broader in scope. Here's a link to the full paper.
From the WUWT comments
October 2, 2014 at 2:16 am
Yes, we all know how sea ice around Antarctica grew rapidly at the end of the last ice age, in response to global warming… :-)
DEEBEE is mistaken about how sea level is likely to change. There could be as much as a one or even two metre rise before 80 years have passed. That's a lot to cope with.
October 2, 2014 at 2:21 am
“With 10 per cent of the world’s population, or 700 million people, living less than 10 metres above present sea level, an additional three metres of sea level rise from the Antarctic alone will have a profound impact on us all.”
This is nonsense. The current population estimate is being used to scare people on an event that might rake almost a 1000 years to develop. So even if it happens, each generation will barely see a few centimeter rise in the seas. Are they expecting people to just marvel at that miniscule a rise and not respond.
chris moffatt has an attack of the Dunning-Krugers and writes:
October 2, 2014 at 3:33 am
So I guess that with all this “layering” the laws of thermodynamics can’t apply to Antarctic ocean waters? So there is no convection or conduction. Terrifying. Where do I donate?
ozspeaksup alerts WUWT (and us) to another new finding:
October 2, 2014 at 3:38 am
Antarctica ice loss weakens gravity
OF all the effects of climate change, the loss of gravity caused by Antarctica’s ice meltdown could be the weirdest — and one of the most worrying.
THIS above in todays adelaide advertiser..and I cant access due to a limit of 2 free page read please, someone go read it and post..it is bound to be hilariously stupid!
Here's a video about it from the European Space Agency's GOCE website. It's neither hilarious nor stupid. It's fascinating (and a worry). Click the squares in the bottom right hand corner to view full screen:
Some exerpts from the ESA article:
...The strength of gravity at Earth’s surface varies subtly from place to place owing to factors such as the planet’s rotation and the position of mountains and ocean trenches.
Changes in the mass of large ice sheets can also cause small local variations in gravity.
Recently, the high-resolution measurements from GOCE over Antarctica between November 2009 and June 2012 have been analysed by scientists from the German Geodetic Research Institute, Delft University of Technology in the Netherlands, the Jet Propulsion Lab in USA and the Technical University of Munich in Germany.
Remarkably, they found that the decrease in the mass of ice during this period was mirrored in GOCE’s measurements, even though the mission was not designed to detect changes over time....
...ESA’s CryoSat satellite, which carries a radar altimeter, has recently shown that since 2009 the rate at which ice is been lost from the West Antarctic Ice Sheet every year has increased by a factor of three.
And, between 2011 and 2014, Antarctica as a whole has been shrinking in volume by 125 cubic kilometres a year....
N. R. Golledge, L. Menviel, L. Carter, C. J. Fogwill, M. H. England, G. Cortese & R. H. Levy "Antarctic contribution to meltwater pulse 1A from reduced Southern Ocean overturning." Nature Communications 5, Article number: 5107 doi:10.1038/ncomms6107
Rohling, Eelco J., Robert Marsh, Neil C. Wells, Mark Siddall, and Neil R. Edwards. "Similar meltwater contributions to glacial sea level changes from Antarctic and northern ice sheets." Nature 430, no. 7003 (2004): 1016-1021. doi:10.1038/nature02859