Top boffins from the British Antarctic Survey say that the Pine Island Glacier - famous as a possible major cause of global-warming-powered sea level rises - was melting just as fast thousands of years ago as it is melting today.

“This paper [just published] is part of a wide range of international scientific efforts to understand the behaviour of this important glacier," explains Professor Mike Bentley, one of the leaders of a BAS effort to find out what's going on with the PIG.

"The results are clear in showing a remarkably abrupt thinning of the glacier 8000 years ago," adds the professor.

The Pine Island Glacier has been much studied over the last two decades, as the rate of ice melting into the sea there has accelerated during those years. Many scientists have theorised that this might be due to global warming caused by human burning of fossil fuels. It's been suggested that the PIG on its own might cause sea levels to rise by several centimetres this century (for background the seas rose about 17cm in the last century. The Intergovernmental Panel on Climate Change expects this to increase massively this century, though there's plenty of research to suggest otherwise.)

However it now appears that the recent rapid flow of the PIG into the sea may just be one of those things that happens from time to time, as it did 8,000 years ago. This is borne out by research from 2010, in which BAS boffins sent a robot submarine under the glacier's projecting ice shelf and found that its acceleration in recent times probably resulted from the fact that it has just finished grinding away a troublesome underwater reef which was slowing it down and causing ice to back up.

The new BAS research on the similar episode 8,000 years ago suggests that the resulting increased ice flow today at the PIG may well go on for some decades yet.

"Based on what we know, we can expect the rapid ice loss to continue for a long time yet," comments the BAS' Joanne Johnson.

It may not, though, or anyway not uninterruptedly. Previous BAS research which came out last month revealed that the most recent ice melt rates for the PIG are the "lowest ever recorded" there, having halved in just two years.

In any case it appears more and more likely that the rapid melting of the PIG's sea ice shelf from the early 1990s to 2010 would have happened anyway, regardless of humanity's carbon emissions. Hearteningly perhaps, the Antarctic sea ice area continues to increase overall, global warming or no.

The new BAS research is published in premier boffinry mag Science. ®