I'm not quite sure what to make of this1, but it seems interesting, and the video is lovely.
There are two papers: Antarctic ice shelf potentially stabilized by export of meltwater in surface river by Robin E. Bell et al., Nature 544, 344–348 (20 April 2017) doi:10.1038/nature22048:
Meltwater stored in ponds and crevasses can weaken and fracture ice shelves... However, surface rivers forming on ice shelves could potentially export stored meltwater and prevent its destructive effects. Here we present evidence for persistent active drainage networks... on the Nansen Ice Shelf in Antarctica that export a large fraction of the ice shelf’s meltwater into the ocean. We find that active drainage has exported water off the ice surface through waterfalls and dolines for more than a century...
and Widespread movement of meltwater onto and across Antarctic ice shelves Jonathan Kingslake et al., Nature 544, 349–352 (20 April 2017) doi:10.1038/nature22049:
Surface meltwater drains across ice sheets... Numerical models of the Antarctic Ice Sheet that incorporate meltwater’s impact on ice shelves, but ignore the movement of water across the ice surface... we have little understanding of Antarctic-wide surface hydrology or how it will evolve. Here we show widespread drainage of meltwater across the surface of the ice sheet through surface streams and ponds (hereafter ‘surface drainage’) as far south as 85° S and as high as 1,300 metres above sea level. Our findings are based on satellite imagery from 1973 onwards and aerial photography from 1947 onwards. Surface drainage has persisted for decades, transporting water up to 120 kilometres from grounded ice onto and across ice shelves, feeding vast melt ponds up to 80 kilometres long.
Perhaps I'm not really doing my job of interpretation here. Never mind.
Notes
1. Nat Geo has a suitably cautious story. Or you may prefer CS Monitor.
2. Female, BTW.
Refs
* Constraining the mass balance of East Antarctica by Alba Martín-Español, Jonathan L. Bamber and Andrew Zammit-Mangion.
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Won't be enough to save the ice sheets from the forthcoming melt. At the current 400+ ppm of carbon dioxide in the mid-Pliocene with that concentration the sea stand was about 25 meters higher; and yes, it was 2+ K warmer...
David - obviously it will make things slightly better than if all that water was going down, but even though I won't live to mid-century I think these recent words from Dana Royer, a paleoclimate researcher at Wesleyan University are about as sobering an assessment in simple terms that I've run across:
“The carbon dioxide levels in the atmosphere today are ones that likely haven’t been reached in 3 million years. But if human activities keep committing carbon dioxide to the atmosphere at current rates, scientists will have to look a lot deeper into the past for a similar period. The closest analog to the mid-century atmosphere we’re creating would be a period roughly 50 million years ago known as the Eocene, a period when the world was completely different than the present due to extreme heat and oceans that covered a wide swath of currently dry land.
“The early Eocene was much warmer than today: global mean surface temperature was at least 10°C (18°F) warmer than today,” Dana Royer, a paleoclimate researcher at Wesleyan University who co-authored the new research, said. “There was little-to-no permanent ice. Palms and crocodiles inhabited the Canadian Arctic.”
I already understood this from paleoclimate studies, but it's really all any layman should need to know about the urgency of reducing CO2 emissions.
Kevin --- Yes but the continents were in sufficiently different positions that ocean circulation was much different than now; Drake passage was closed so no circumpolar Antarctic circulation and the Panama seaway was wide open in the Eocene.
By 40 million years ago Drake passage began to open and by, anway, 4 million years ago the Panama seaway was completely closed. Thus the ocean circulation became the modern one by then.
I don't trust saying that the future will be like the past longer ago than the mid-Pliocene for that reason. In any case, 25 meters higher and 2+ °C warmer is quite disastrous enough.
David, IIRC model experiment s done in the last several years point to seaway opening/closing as being much less important to global climate than previously thought.
That said, it may be that looking just at quasi-equilibrium states (quasi since Milankovitch cycles continue to have their influence) misses the potentially large effects of the entirely unnatural rate at which we're forcing the climate.
#1
"... was about 25 meters higher ..."
Sounds good: Shortens the way to the beach.
The site:
http://flood.firetree.net/
Is a good site for investigating what sea level rise will do to your beach journey.. (ProTip: If in Cambridge, don't buy a house north of the A14, if you want to keep it for a few generations)
It's also worth looking at the major cities from Chennai all the way around the East Asia coast to Tianjin in China, with Eemian max sea levels. They get it lot worse than the US and Europe (with apologies to Holland and Hull, obvs)
#2 If you read the referenced paper, we don't get to Eocene like climate until we get something close to or more than 1000 PPM, and wait for thermal inertia. Decades into the future.
#3 From my reading of journal papers, location of the continents does not have a strong influence on global climate, at least in modern climate models, at least for most but not all configurations of climates.
Yes, mid-Pliocene is a better analogy for decades more, for the reasons of CO2 levels, the massive thermal inertia of the oceans and ice sheets and lastly the locations of the continents. I don't fully trust analogy as the climate will not be in equilibrium for centuries.
On 2017/04/25, Markus opined:
“… was about 25 meters higher …”
Sounds good: Shortens the way to the beach.
Yeah, or maybe not. Bit hard to get to the beach when the road is crowded with climate refugees.
Also, I'm not clear where the money will come from to maintain those roads once 50% of our society's economic activity is eliminated by rising seas.
Location of the continents appears to have mattered:
https://en.m.wikipedia.org/wiki/Snowball_Earth
and to establish modern climate at least Drake Passage has to be open and, I opine, the Panama Seaway closed. For it issue from the mid-Pliocene that the modern decline in carbon dioxide starts.
Sealevel variations at Panama:
http://onlinelibrary.wiley.com/doi/10.1029/JZ068i020p05701/abstract
with an average being 20 cm higher on the Pacific side in comparison to the Caribbean side. So when there was a Panama Seaway there would have been a considerable current through it, although not enough to keep the seaway open. I opine that seaway and it's current made a difference to the global climate.
MSL was at least 6m higher during the Eemian highstand (GAT 1 - 2C above present) with all ocean gateways in their Holocene configurations. That's enough for me.
The question raised by the articles WMC quotes is: are there factors that inhibit the recently hypothesised rapid rate of ice sheet collapse?
“… was about 25 meters higher …”
Sounds good: Shortens the way to the beach.
The beach would be closer to my front door, but the swim uphill would take longer than the walk down does.
http://en-au.topographic-map.com/places/Bondi-Beach-9521140/
#10 One the the benefits of climate models is more insight into the past climate.
Closing the Isthmus of Panama is modeled to have a large impact warming on the North Atlantic, but little on global conditions. Net difference in global temperature is 0.3C (from table 1)
Lunt, D.J., Valdes, P.J., Haywood, A. et al. Clim Dyn (2008) 30: 1. doi:10.1007/s00382-007-0265-6
http://rd.springer.com/article/10.1007/s00382-007-0265-6
400 ppm of CO2 after ~560 years of simulation gives about 3.1C net difference in global temperature. An order of magnitude greater.
I vote we do the experiment. How many gigatons of nukes would it take to REALLY open the Panama seaway? And could we build a dam between South America and the Antarctic Pennisula? Some grant applications need writing..
#13 --- Yes, that is about what I expected. Unfortunately the provided abstract doesn't state the carbon dioxide concentration used in the model runs.
On 2017/04/26, Andrew Dodds joked:
"... And could we build a dam between South America and the Antarctic Pennisula?"
As a Patrick O'Brien fan, I have a vivid image of what the Magellan Strait is like.
Construction activity there? Wow, that would keep Nat Geo TV channel in business for years....
#15 I have library access to the full paper. The Panama closed vs Panama open was done at 400 ppm.
Bemused. These factors have operated "forever" . Just because some one observes them does not make the melting or freezing any faster or slower than it ever was.
#17 --- Thanks.