London: The Earth’s glaciers are seriously out of balance with the global climate and are already on their way to losing almost 40 percent of their volume, a new study has revealed.
The researchers reached this result after studying a representative group of 144 small and large glaciers around the world.
Their figure assumes no further warming of the climate.
However, if temperatures continue to rise as models predict, the wastage will be even higher, the team said.
“When we look at the data, we can see that the glaciers are out of balance, meaning the climate has actually changed faster than the changes we’ve seen in ice area and volume,” the BBC quoted Sebastian Mernild from Los Alamos National Laboratory, New Mexico, US, as saying.
“Our data suggests the glaciers will commit about 30 percent of their area and about 38 percent of their volume to global sea level rise,” he said.
Mernild’s group calculated this figure to be on the order of 22cm.
“This will happen in the next decades to centuries,” he said.
A glacier is in balance when the snow at higher, colder elevations equals the volume of snow and ice lost through melting at lower, warmer elevations.
If precipitation is greater, the glacier will increase its mass; if melting dominates, the glacier will thin and retreat until it reaches a state of equilibrium again.
The researchers said that their assessment of the glacier sample indicates climate conditions have changed so fast that many ice bodies have not had time yet to fully adjust.
This means a certain amount of mass loss is already locked into the system even if there is no further warming.
“Glaciers will move up in the terrain, they will become smaller and thinner and they will adjust to the climate conditions.
“On the other hand, we expect the climate will warm continuously in the future, meaning that the glaciers will become even more out of balance, and that means the glaciers will commit even more volume to sea level rise,” he said.
If the models are correct and further warming is seen during the next several decades and longer, the study projects that the Earth`s glaciers could ultimately lose more than half their mass.
The picture is described as regional, with some areas said to be more out of balance than others.
Dr Mernild cites the Alps as one glacier group that is farther from balance than the global average.
He says alpine glaciers are likely to lose most of their mass by 2100.
"But if you take into account the volume of ice in the glaciers here in the Alps, it won``t have the same impact on the global sea level rise compared to if we see the same out of balance conditions in other places on the globe where we know there is more ice located.
"So, the contribution to sea level rise will not be that big from the Alps region."
The COSIM assumption is that there is a sea level equivalent of 60cm locked away in all the world’s glaciers (the number excludes the ice sheets of Antarctica and Greenland).
That figure has been debated here at EGU. Dr Matthias Huss, from the University of Fribourg, Switzerland, presented new data suggesting there was only 48cm of sea level tied up in all the world’s glaciers (and the larger glaciers referred to as ice caps).
“Our number is 192,000 cu km. This is about 25 percent less than some previous estimates. It is a total potential sea-level rise of 0.48m," Huss said.
“We’re using a physically based approach. Until now, people have relied on simple statistical methods,” Huss said.
The study was presented at the European Geosciences Union (EGU) meeting in Vienna, Austria.