Dire predictions from new global ice melt calculations
Global ice loss has increased rapidly over the past two decades, and scientists are still underestimating just how much sea levels could rise, according to alarming new research published this month.
From the thin ice shield covering most of the Arctic Ocean to the mile-thick mantle of the polar ice sheets, ice losses have soared from about 690 billion tonnes per year in the 1990s to more than 1trillion tonnes per year in the 2010s, a new study released yesterday shows. That is an increase of more than 60 per cent, equating to 25 trillion tonnes of melted ice in total – and it means that roughly 3 per cent of all the extra energy trapped within Earth’s system by climate change has gone toward turning ice into water.
‘‘That’s like more than 10,000 Back to the Future lightning strikes per second of energy melting ice around-the-clock since 1994,’’ said William Colgan, an ice-sheet expert at the Geological Survey of Denmark and Greenland.
‘‘That is just a bonkers amount of energy.’’
There is good reason to think the rate of ice melt will continue to accelerate. A second, Nasabacked study on the Greenland ice sheet, for instance, finds that no less than 74 major glaciers that terminate in deep, warming ocean waters are being severely undercut and weakened.
And it asserts that the extent of this effect, along with its implications for rising seas, is still being discounted by the global scientific community.
Failing to fully account for the role of ocean undercutting means sea-level rise from the ice sheets may be underestimated by ‘‘at least a factor of 2,’’ the new paper in the journal Science Advances finds.
‘‘It’s like cutting the feet off the glacier rather than melting the whole body,’’ said Eric Rignot, a study co-author and a glacier researcher at Nasa’s Jet Propulsion Laboratory and the University of California, Irvine. ‘‘You melt the feet and the body falls down, as opposed to melting the whole body.’’
‘‘I think this is an example that the current projections are conservative,’’ Rignot said. ‘‘As we peer below we realize these feedbacks are kicking in faster than we thought.’’
Together, the two studies present a worrying picture.
The first finds that the current ice losses, which are accelerating quickly, are on pace with the worst scenarios for sea-level rise put out by the United Nation’s Intergovernmental Panel on Climate Change (IPCC). That expert body found that ice sheets could drive as much as 40cm of sea-level rise by 2100.
But on top of that, the new Nasa work on Greenland suggests that the IPCC, whose sea-level projections have long been faulted as being conservative, could underestimate future sealevel rise if the panel, which has a new report expected later this year, does not take full account of the power of the ocean to knock the ice backward and undermine it.