19 Feb 2025
Ice melting from glaciers around the world is depleting regional freshwater resources and driving global sea levels to rise at ever-faster rates.
According to new findings, through an international effort involving 35 research teams, glaciers have been losing an average of 273 billion tonnes of ice per year since the year 2000 – but hidden within this average there has been an alarming increase over the last 10 years.
In the year 2000, glaciers – excluding the continental ice sheets of Greenland and Antarctica – spanned 705,221 sq km, and held an estimated 121,728 billion tonnes of ice.
Over the past two decades, they have lost approximately 5% of their total volume, with regional losses ranging from 2% on the Antarctic and Subantarctic Islands, to 39% in Central Europe.
This corresponds to an annual loss of 273 billion tonnes of ice. However, the amount of ice being lost jumped by 36% in the second half of the study period (2012–2023) compared to the first half of the study (2000–2011).
Glacier mass loss over the whole study period was 18% higher than that from the Greenland Ice Sheet and more than double that from the Antarctic Ice Sheet.
The Glacier Mass Balance Intercomparison Exercise
The research, which was published today in the journal Nature, was conducted as part of the Glacier Mass Balance Intercomparison Exercise, or Glambie for short.
Glambie is a major research initiative coordinated by the World Glacier Monitoring Service (WGMS) hosted at the University of Zurich, in collaboration with the University of Edinburgh and Earthwave Ltd to generate a community estimate of glacier mass loss globally.
The team coordinated the compilation, standardisation and analysis of different data from field measurements and from a wealth of different types of optical, radar, laser and gravimetry satellite missions.
Satellite observations included those from the US Terra/ASTER and ICESat-2, the US–German GRACE, the German TanDEM-X and ESA’s CryoSat missions, among others.
By combining different types of data from these multiple sources, Glambie produced an annual time series of glacier mass change for all glacier regions globally from 2000 to 2023.
“We compiled 233 estimates of regional glacier mass change from about 450 data contributors organised in 35 research teams,” explained Michael Zemp, who co-led the study.
“Benefiting from the different observation methods, Glambie not only provides new insights into regional trends and year-to-year variability, but we could also identify differences among observation methods. This means that we can provide a new observational baseline for future studies on the impact of glacier melt on regional water availability and global sea-level rise.”
Livia Jakob, who hosted a large workshop at Earthwave in Edinburgh to discuss findings with all the participants, noted, “Bringing together so many different research teams from across the globe in a joint effort to increase our understanding and certainty of glacier ice loss has been extremely valuable. This initiative has also fostered a stronger sense of collaboration within the community.”
Impacts on regional freshwater resources and global sea level
Between 2000 and 2023, glaciers collectively lost 6542 billion tonnes of ice, contributing 18 mm to global sea-level rise. On average, glaciers lost 273 billion tonnes of ice per year, equivalent to an annual sea-level rise of 0.75 mm.
The rate of glacier ice loss has increased significantly from 231 billion tonnes per year in the first half of the study period to 314 billion tonnes per year in the second half.
Today, glaciers rank as the second-largest contributor to global sea-level rise, following ocean warming related thermal expansion. They surpass the contributions of the Greenland Ice Sheet, the Antarctic Ice Sheet, and changes in land water storage.
In addition to rising sea levels, glacier melt represents a significant loss of regional freshwater resources.
“To put this in perspective, the 273 billion tonnes of ice lost annually amounts to what the entire global population consumes in 30 years, assuming three litres per person and day,” noted glaciologist Prof. Zemp.
UZH glaciologist Inés Dussaillant, who was involved in the Glambie analyses, added, “Glaciers are vital freshwater resources, especially for local communities in Central Asia and the Central Andes, where glaciers dominate runoff during warm and dry seasons.
“But when it comes to sea-level rise, the Arctic and Antarctic regions, with their much larger glacier areas, are the key players. However, almost one-quarter of the glacier contribution to sea-level rise originates from Alaska.”
Noel Gourmelen who co-led the study, said, “The research is the result of sustained efforts by the community and by space agencies over many years, to exploit a variety of satellites that were not initially specifically designed for the task of monitoring glaciers globally.
“This legacy is already producing impact with satellite missions being designed to allow operational monitoring of future glacier evolution, such as Europe’s Copernicus CRISTAL mission which builds on the legacy of ESA’s CryoSat.”
The research was primarily funded by the Science for Society element of ESA’s FutureEO programme, with additional support from the International Association for Cryospheric Sciences and various institutional partners.
It was conducted by the Glambie team under the leadership of the WGMS and of the University of Edinburgh, and in collaboration with Earthwave Ltd., and over 30 other research teams from around the world.
ESA Earth Observation Applications Scientist, Stephen Plummer, said, “We take great pride in supporting this vital research through our ESA Science for Society programme element as it brings together, for the first time, multiple estimates of glacier mass loss from different satellites and in situ observations through a community driven approach.
“These findings are not only crucial for advancing our scientific understanding of global glacier changes, but also provide a valuable baseline to help regions address the challenges of managing scarce freshwater resources and contribute to developing effective mitigation strategies to combat rising sea level.”
Notably, the study marks an important milestone in preparation for this year’s United Nations’ International Year of Glaciers’ Preservation and the Decade of Action for Cryospheric Sciences (2025–2034).
[Image]
(A) Glacier ice loss 2000–2023
(B) Chugach Mountains, Alaska
(C) ESA's ice mission
(D) Golubin Glacier, Kyrgyzstan, 2012