Pine Island Glacier itself is grounded on an underwater sill where the grounding line is retreating. At 100--200 meters per annum, if memory serves. Eventually the slope becomes downward inland and then, presumably, the breakup rate will increase; this time in grounded ice and so increase the sea level.
A similar process already happened at a much smaller scale in Icy Bay, Alaska, north of Mount Fairweather. As I recall reading about it, 50 years sufficed to eliminate the glacier in the bay.
At the current carbon dioxide concentration of over 400 ppm the conditions for a return to the mid-Pliocene are set. Check the Wikipedia page on Pliocene climate; a global temperature increase of 2--3 °C warmer than now and a sea level rise of about 25 meters higher than now, this at equilibrium.
Various glaciologists opine that the Greenland Ice Sheet will melt in about a thousand years, adding 9 meters to the sea stand. What about Antarctica?
Post by Roger Clifton on Sept 29, 2017 16:50:16 GMT 9.5
Remarkably, the thickness of the Pine Island Glacier has been decreasing at a rate exceeding 1 m a year. Where a glacier lifts off bedrock, warming water from the wider ocean penetrates beneath it and by melting, thins it all the more. Around the world, average gradients at water's edge mean that high water mark creeps inland by 200 m for every 1 m of sea level rise. However, at PIG the bedrock actually sinks as you go up the glacier, so the warming water beneath it is or will soon be penetrating inland much faster than 200 m per year.
Some experts believe that ocean water is circulating under most of the PIG and much of the West Antarctic Ice Sheet, causing the thinning. Being more conductive than ice or bedrock, I would have thought the ocean water would be visible on the radar returns. That would show its presence but not the speed of warming water. Perhaps we will be told in due course.
Post by Roger Clifton on Sept 30, 2017 22:05:28 GMT 9.5
In modern Greenland, the slumping ice sheet accelerates when rainwater, having sunk through the ice, joins the bottom cheesy layer or forms a shear layer above it. But I guess that's more about mobility than melting. In Antarctica, the cheesy layer is mainly softened by geothermal flux and flows faster than the ice above it. Near the bottom of the famous ice cores the climate record is obliterated by such mixing.
How would you read the ice patterns in these radar images?
This news about the Pine Island Glacier and its relationship to the mid-Pliocene is depressing, but also motivating: Surely we as a species can do better. The Washington Post had a good article about these matters in 2016, written for the interested layman. An excerpt:
"But even under a more moderate emissions scenario, Wednesday's study found that the Antarctic contribution to sea level still could reach about two feet by 2100, and much more by 2500. Only if countries sharply reduce emissions does the model show that it's possible to preserve Antarctica in roughly its current state.
"'This research highlights the importance of doing even much better than the Paris agreement if we're going to save our coastal cities,' Strauss said."
From: "Scientists nearly double sea level rise projections for 2100, because of Antarctica" by Brady Dennis and Chris Mooney March 30, 2016
Post by David B. Benson on Oct 3, 2017 11:53:28 GMT 9.5
Yes, much better than the Paris Agreement. For even eliminating all excess emissions of carbon dioxide and other heat trapping gasses still leaves the excess already emitted. So a responsible removal program is required. I advocate growing trees in major deserts via a massive irrigation project but other methods are also available.
There would still be some sea level rise and yesterday's newspaper from Australia, I don't recall which one, gave some projections for various cities in Australia.