New research has shown that global glacier retreat has accelerated over the last two decades. Though their shrinking has been evident for some time, this new work, published in Nature, shows that the reduction has massively accelerated in the last two decades.
The team used detailed satellite observations to study 217,175 glaciers from around the world, excluding ice sheets. These estimates were validated with independent high-precision measurements of individual glaciers. From this, the group of international researchers were able to work out the changes in volume and mass which revealed the dramatic decline observed among glaciers in the 21st century.
Between 2000 and 2019, glaciers have lost an average of 267 gigatons of mass per year. This loss accounted for over one-fifth of the sea-level rise observed around the world. Each decade of this century has seen an increase of 48 gigatons per year in glacier mass loss, corresponding to an acceleration of sea-level rise between six and 19 percent.
The team estimates that sea-level rise due to glacier melt has been of the order of 0.74 millimeters. The remaining is due to thawing ice sheets from Greenland and Antarctica, changes in how water is stored on the planet, and thermal expansion of water across the planet in response to higher average temperatures.
“The situation in the Himalayas is particularly worrying,” lead author Romain Hugonnet, from the ETH Zurich and the University of Toulouse, said in a statement emailed to IFLScience. “During the dry season, glacial meltwater is an important source that feeds major waterways such as the Ganges, Brahmaputra and Indus rivers. Right now, this increased melting acts as a buffer for people living in the region, but if Himalayan glacier shrinkage keeps accelerating, populous countries like India and Bangladesh could face water or food shortages in a few decades.”
The graph shows the loss of thickness of Icelandic glaciers between 2000 and 2019 (in red) and the surprising gains due (blue). Image Credit: Hugonnet et al., Nature
Understanding these global changes can help us model local changes and better prepare for the consequences that the climate crisis is unleashing upon the world. The team discovered that certain regions seem to have been spared from this dramatic reduction trend. Greenland’s east coast and parts of Iceland and Scandinavia appear to have bucked the trend. This is due to a weather anomaly in the North Atlantic that led to higher precipitation and lower temperatures between 2010 and 2019 in those regions.
At the same time, other portions of Iceland (as well as Alaska and the Alps) exhibit the fastest melting glaciers analyzed in the survey. Also, a previously stable and even growing glacier region, the Karakoram mountain range in Asia, is now experiencing intense mass loss.
“Our findings are important on a political level. The world really needs to act now to prevent the worst-case climate change scenario,” added co-author Daniel Farinotti, head of the glaciology group at ETH Zurich and the Swiss Federal Institute for Forest, Snow and Landscape Research WSL.
