Melting Glaciers Accelerate Freshwater Loss and Global Sea-Level Rise

Melting Glaciers Accelerate Freshwater Loss and Global Sea-Level Rise
by Robert Schreiber
Berlin, Germany (SPX) Feb 20, 2025

Glaciers, distinct from the massive ice sheets of Greenland and Antarctica, covered an area of 705,221 square kilometers globally in 2000 and held approximately 121,728 billion tons of ice. Since then, glaciers have collectively lost around 5% of their ice volume, with regional variations ranging from a 2% loss in the Antarctic and Subantarctic Islands to a striking 39% decline in Central Europe. On an annual basis, glaciers have shed 273 billion tons of ice, a loss that has surged by 36% between the first (2000-2011) and second (2012-2023) halves of the study period. This level of glacier mass loss surpasses the annual ice loss from the Greenland Ice Sheet by 18% and is more than double that of the Antarctic Ice Sheet.

An international team of researchers, led by the World Glacier Monitoring Service (WGMS) at the University of Zurich (UZH), conducted the Glacier Mass Balance Intercomparison Exercise (GlaMBIE). This initiative brought together experts from around the world to compile, standardize, merge, and analyze data from both field studies and satellite observations. The team synthesized findings from 233 regional glacier mass change estimates, contributed by approximately 450 researchers across 35 teams.

"By integrating various observation techniques, GlaMBIE not only enhances our understanding of regional trends and annual fluctuations but also allows us to identify discrepancies between methods, presenting opportunities to refine future assessments," explained Michael Zemp, a geography professor at UZH and the study's lead researcher.

Declining Freshwater Supplies and Rising Seas

Between 2000 and 2023, global glacier mass loss reached 6,542 billion tons, adding 18 millimeters to global sea levels at an average annual rate of 273 billion tons, equivalent to 0.75 millimeters of sea-level rise per year. Glaciers now rank as the second-largest driver of rising sea levels, following ocean warming and preceding ice loss from Greenland, land water storage changes, and Antarctica.

Beyond sea-level impacts, glacier retreat also threatens vital freshwater reserves. "To put this into perspective, the 273 billion tons of ice lost annually equate to what the global population would consume in 30 years, assuming a daily intake of three liters per person," noted Zemp.

Glaciers serve as crucial freshwater sources, particularly for communities in Central Asia and the Central Andes, where they sustain water supplies during warm and dry seasons. "However, in terms of sea-level rise, the most significant contributors are glaciers in the Arctic and Antarctic regions, which hold extensive ice reserves. Nearly a quarter of the glacier-related sea-level rise stems from ice loss in Alaska," added UZH glaciologist Ines Dussaillant, a key participant in the GlaMBIE analysis.

Mitigating the Impact Through Climate Action

This study coincides with the International Year of Glaciers' Preservation in 2025 and the United Nations' Decade of Action for Cryospheric Sciences (2025-2034). GlaMBIE establishes a new observational benchmark that will support improved forecasting of future freshwater availability and sea-level changes.

"Our findings and recent modeling efforts indicate that glacier ice loss will persist and potentially intensify through the end of this century," said Samuel Nussbaumer, UZH glaciologist and GlaMBIE project manager. "This underscores the urgent call from the Intergovernmental Panel on Climate Change for immediate and decisive action to curb greenhouse gas emissions. Reducing emissions is essential to mitigate the impacts of glacier shrinkage on local hazards, regional water supplies, and global sea levels," he concluded.

Research Report:Community estimate of global glacier mass changes from 2000 to 2023