The world’s glaciers have lost nearly three billion tonnes of ice from 2010 to 2020 due to climate change, scientists have found.
Europe’s Cryosat spacecraft tracked the 200,000 or so glaciers on Earth and found they have lost 2,720bn tonnes of ice in a decade - equivalent to losing 2% of their bulk.
Cryosat is a veteran European Space Agency Earth observer which carries an instrument called a radar altimeter. This sends down microwave pulses to trace variations in height along the planet’s surface - and in particular the changes in elevation of ice fields.
This type of instrument works really well when monitoring ice in the interior of Antarctica and Greenland but it finds it more tricky to measure ice across rugged terrain such as in steep-sided valleys.
However, advances in data processing have enabled scientists to effectively increase the resolution and robustness of Cryosat’s vision so that it can now track developments even in those tricky locations.
Scientists have now been able to obtain their best satellite assessment yet of the status of the world’s glaciers.
The study, reported on Wednesday (26 April) in the journal Geophysical Research Letters, has produced a global glacier assessment.
It found that Alaska’s glaciers have experienced the greatest losses, losing more than 80 billion tonnes of ice a year which equates to about 5% of the total ice volume in the region during the 10-year study period.
Places where glaciers appear to be eroding and moving faster because their fronts end in warmer waters include the Arctic - at Svalbard, the Norwegian archipelago - and in the Russian sectors of the Barents and Kara seas.
Increasing ice discharge into the ocean accounts for over 50% of mass loss in these areas.
The satellite’s observations indicate the vast majority of the ice loss seen between 2010 and 2020 was due to melting in an ever warmer atmosphere.
Only 11% of the loss was the result of glaciers experiencing melting or increased flow because their fronts terminate in warmer ocean or lake waters.
Noel Gourmelen from Edinburgh University told BBC News that “usually surface waters of the Arctic Ocean are cold and fresh but increasingly in some of these places the surface waters are becoming more salty and warmer as currents move up from the Atlantic.”
He said “this means glaciers are dumping more ice into the ocean.”
This will add to sea-level rise which already threatens low-lying communities.
Monitoring how quickly glaciers are changing is important because millions of people rely on them for drinking water and farming.
In many parts of the globe glaciers function as critical water reservoirs. More than 20% of the world’s population is thought to be dependent in some way on summer melt waters that flow from glaciers.
For the vast majority, observation from space is the only way to keep an eye on how they are responding to climate change.