This image from 2008 shows deep crevasses in Pine Island Glacier (in the square), indications of its rapid movement. Photo: NASA.
Some new research on the rapidly melting Pine Island Glacier in Antarctica offers some more detail on why it is losing ice so precipitously. Scientists from the British Antarctic Survey and the Lamont-Doherty Earth Observatory, using remote underwater vehicles, have discovered that an underwater ridge had been slowing the glacier's flow into the sea, but as the glacier has thinned it has become disconnected from that ridge.
photo: British Antarctic Survey
This has both allowed the glacier to move more rapidly towards the sea and allowed deep warm ocean water to get underneath the glacier. This is forming a cavity some 1000 square kilometers in size under the ice shelf which is causing the bottom of the shelf to melt, further accelerating ice loss.
Dr Adrian Jenkins of the BAS:
The discovery of the ridge has raised new questions about whether the current loss of ice from Pine Island Glacier is caused by recent climate change or is a continuation of a longer-term process that began when the glacier disconnected from the ridge.
We do not know what kick-started the initial retreat from the ridge, but we do know that it started some time prior to 1970. Since detailed observations of Pine Island Glacier only began in the 1990s, we now need to use other techniques such as ice core analysis and computer modeling to look much further into the glacier's history in order to understand if what we see now is part of a long term trend of ice sheet contraction. This work is vital for evaluating the risk of potential wide-spread collapse of West Antarctic glaciers.
Earlier this year, scientists determined that the Pine Island Glacier has likely passed a tipping point and once it melts completely it alone will contribute 9 inches to global sea level rise.
Currently, thinning ice in West Antarctica is responsible for about 10% of observed sea level rise.
More on Global Climate Change:
West Antarctic Glacier Disintegrating Rapidly: First Hand Account
Get Ready for 7 Foot Sea Level Rise by 2100 + Antarctic Glacier Past Tipping Point
Antarctica's Pine Island Glacier Melting Four Times Faster Than 10 Years Ago