Vast ice sheet more vulnerable to climate change than previously thought, say scientists
Pic: Christine Zenino
By Sophie Yeo
The Greenland ice sheet is more vulnerable to climate change than previously thought, say scientists.
A new model developed by researchers at the University of Cambridge shows that the enormous ice sheet – which contains enough to water to raise the ocean by more than seven metres if lost altogether – will become much more vulnerable as temperatures rise.
The model uses new evidence which shows that the ground beneath the ice sheet is soft and spongy, rather than the hard and impermeable bedrock assumed by previous studies.
“”The soft sediment gets weaker as it tries to soak up more water, making it less resistant, so that the ice above moves faster,” said Dr Poul Christoffersen from Aberystwyth University, who worked on the study.
The soft, slippery ground will be forced to absorb more water as the climate warms, as pools of water form on the surface of the glacier, before filtering down to the bottom.
This makes the ground even more slippery, causing the ice to flow more quickly into the sea, causing the oceans to rise.
Limits
The study, which is published in Nature Communications, eventually concludes that there is a limit to how much water can be stored beneath the Greenland ice sheet, which makes it sensitive to climate change, as well as extreme weather events including rainfall and heatwaves.
“When these large ice sheets melt, whether that’s due to seasonal change or a warming climate, they don’t melt like an ice cube,” said Dr Marion Bougamont of Cambridge’s Scott Polar Research Institute, explaining that water is lost from both the surface and the movement of the glaciers.
How far these moving chunks of ice – a chunk eight times the size of the UK in Greenland’s case – will impact sea level rise remains uncertain.
Surface melting from the Greenland ice sheet alone is causing 0.6mm of sea level rise every year. In total, oceans are rising 3mm annually.
This is particularly worrying for coastal communities and small island nations, which are seeing their land eroded and their vulnerability to extreme weather events increasing as a result.
California drought
Separately, scientists at Stanford University say that the drought in California is “very likely” linked to climate change.
California is currently facing one of its worst droughts on record, which a recent report said will cost the state $2.2 billion and around 17,000 jobs.
The drought has been caused by a ridge of high pressure in the atmosphere, which has caused Pacific storms to bypass California, Oregon and Washington. This means that any rain and snow that would normally fall on the West Coast were instead diverted to Alaska.
In a study published this week in a supplement to the Bulletin of the American Meteorological Society, scientists are now saying that this ridge was much more likely to form in conditions of higher greenhouse gas levels.
“Our research finds that extreme atmospheric high pressure in this region—which is strongly linked to unusually low precipitation in California—is much more likely to occur today than prior to the human emission of greenhouse gases that began during the Industrial Revolution in the 1800s,” said Noah Diffenbaugh, a climate scientist at Stanford University.
He added: “This isn’t a projection of 100 years in the future. This is an event that is more extreme than any in the observed record, and our research suggests that global warming is playing a role right now.”