The bases of the glaciers seem to be slipping more easily over the rock than in the past, so they slide into the sea faster… it is possible that melting ice at the surface is boring holes through the ice sheets and lubricating their base.
Global warming might be speeding up this process.
Duncan Wingham and Andrew Shepherd from the University of Edinburgh, UK, have found that four glaciers retreating in unison are all in direct contract with the sea. This mans that relatively small changes in sea temperature could have a disproportionate effect on ice loss.
“Our assessment confirms that just one type of glacier in Antarctica is retreating today – those that are seated in deep submarine basins and flow directly into the oceans,” says Shepherd. These glaciers are vulnerable to small changes in ocean temperature, such as those that have occurred over the 20th century and those predicted for the 21st century. A rise of less than 0.5oC could have triggered the present imbalance.”
(“What’s behind the big meltdown?”, New Scientist Vol 2591 24th March 2007 pp 16,17)