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Study: further melting of Antarctic glacier half the size of Germany is 'irreversible'

An international group of researchers has found that the largest glacier in West Antarctica is "retreating inland" faster than ever.

A 30-mile-long iceberg calving off Pine Island Glacier, in 2011. (Photo: NASA)

In this week’s New Statesman I wrote about the misadventures of the MV Akademik Shokalskiy, the research vessel trapped in ice off the shore of Antarctica, and why “one localised incident does not disprove the vast body of evidence demonstrating that the world is heating up, decade by decade”.

There’s been an increase in the amount of ice in the sea around Antarctica, which - compared to the continually-shrinking ice in the Arctic - reassures sceptics that they were right about this climate change brouhaha all along. But, of course, that’s not the case at all. The ice on the land (the ice that, when it melts, raises sea levels) is decreasing, and while sea ice is increasing, that’s probably because the run-off from the land is diluting the sea, raising its freezing point.

Categorising that melt is difficult, as, compared to the Arctic, Antarctica is much more massive and much less well-documented landmass with a wider range of climates. As an example, a new study in Nature Climate Science has found that the Pine Island Glacier, in West Antarctica, has found that it may have entered an “irreversible” melting period where the amount of water it unloads into the ocean increases five-fold.

The 175,000km2 glacier - that’s about half as big as Germany - is responsible for draining a quarter of the West Antarctica ice sheet by itself, and regularly calves off huge icebergs into the Southern Ocean. The Natural Environment Research Council’s (NERC) British Antarctic Survey has found that it’s “retreating inland”, a sign that its melt is increasing. It’s bad news. Very bad.

Here’s the NERC’s news site, Planet Earth Online:

'At the Pine Island Glacier we have seen that not only is more ice flowing from the glacier into the ocean, but it's also flowing faster across the grounding line - the boundary between the grounded ice and the floating ice. We also can see this boundary is migrating further inland,' says Dr G Hilmar Gudmundsson from NERC's British Antarctic Survey, a researcher on the project.

All the models agreed that the Pine Island Glacier has become unstable, and will continue to retreat for tens of kilometres.

'The Pine Island Glacier shows the biggest changes in this area at the moment, but if it is unstable it may have implications for the entire West Antarctic Ice Sheet,' says Gudmundsson. 'Currently we see around two millimetres of sea level rise a year, and the Pine Island Glacier retreat could contribute an additional 3.5 - 5 millimeters in the next twenty years, so it would lead to a considerable increase from this area alone. But the potential is much larger.'

A doomsday scenario, where the entire West Antarctica ice sheet melted away, would cause a sea level rise of five metres. That’s not what’s being forecast here, but the level of melt is illustrative of a crucial threat to the world from climate change - even if we were to stop producing gases that cause the net warming effect today, many of their effects are now locked-in and inevitable.