By Summit Voice
FRISCO — The world’s largest ice sheet could be more vulnerable to the effects of climate change than previously thought, according to new research from Durham University. Using declassified spy satellite images, the researchers created a long-term record of changes in the ice sheet’s outlet glaciers.
The mapping, spanning 50 years, from 1963 to 2012, shows that the glaciers underwent rapid and synchronized periods of advance and retreat which coincided with cooling and warming. Large parts of the ice sheet, which reaches thicknesses of more than 4 kilometers, could be more susceptible to changes in air temperatures and sea-ice than previously believed.
Based on their study the Durham team said there is an urgent need to understand the vulnerability of the East Antarctic Ice Sheet, which holds the vast majority of the world’s ice — enough to raise global sea levels by more than 50 meters. The findings were published 28 August in the Nature.
“We know that these large glaciers undergo cycles of advance and retreat that are triggered by large icebergs breaking off at the terminus, but this can happen independently from climate change,” said Durham geography professor Dr. Chris Stokes. “It was a big surprise therefore to see rapid and synchronous changes in advance and retreat, but it made perfect sense when we looked at the climate and sea-ice data.
“When it was warm and the sea-ice decreased, most glaciers retreated, but when it was cooler and the sea ice increased, the glaciers advanced.
“In many ways, these measurements of terminus change are like canaries in a mine – they don’t give us all the information we would like, but they are worth taking notice of.”
The researchers found that despite large fluctuations in terminus positions between glaciers – linked to their size – three significant patterns emerged:
- In the 1970s and 80s, temperatures were rising and most glaciers retreated;
- During the 1990s, temperatures decreased and most glaciers advanced;
- And the 2000s saw temperatures increase and then decrease, leading to a more even mix of retreat and advance.
Trends in temperature and glacier change were statistically significant along the East Antarctic Ice Sheet’s warmer Pacific Coast, but no significant changes were found along the much cooler Ross Sea Coast, which might be expected if climate is driving the changes, the Durham researchers said.
Dr Stokes said that the cause of the recent trends in air temperature and sea ice were difficult to unravel but were likely to reflect a combination of both natural variability and human impacts.
However, he added that the changes observed in glaciers in East Antarctica needed further investigation against the backdrop of likely increases in both atmospheric and ocean temperatures caused by climate change.
Dr Stokes said: “If the climate is going to warm in the future, our study shows that large parts of the margins of the East Antarctic Ice Sheet are vulnerable to the kinds of changes that are worrying us in Greenland and West Antarctica – acceleration, thinning and retreat.
“When temperatures warm in the air or ocean, glaciers respond by retreating and this can have knock-on effects further inland, where more and more ice is drawn-down towards the coast.
“We need to monitor their behavior more closely and maybe reassess our rather conservative predictions of future ice sheet dynamics in East Antarctica.”