which poses a threat to rising sea levels and water shortages. New study published in the journal Nature reveals that global glaciers lost an average of 273 ± 16 gigatons per year from 2000 to 2023. This melting contributes to the increase sea levels and has an impact on ecosystems, freshwater resources, and global water and energy cycles.

Key findings of the study:

• Accelerating melting: The rate of glacier melt increased by 36 ± 10 % between the first (2000–2011) and second (2012–2023) half of the monitoring period.
• Record losses in 2023: The last five years (2019–2023) include four years with the largest annual ice losses, with 2023 seeing a record loss of 548 ± 120 gigatons.
• Significant contribution to sea level rise: Glacier losses have contributed to global sea level rise of 18 ± 1 mm since 2000, with an average annual change of 0.75 ± 0.04 mm.
• Regional differences: All 19 monitored regions experienced glacier mass losses, with Alaska (22 %), the Canadian Arctic (20 %), the Greenland Ice Sheet (13 %) and the southern Andes (10 %) accounting for the largest share of global losses.
• Impact on small glacial areas: The largest relative ice losses occurred in areas with small glacier area, such as central Europe (-39 %), the Caucasus (-35 %), and New Zealand (-29 %).

Study methodology:

The GlaMBIE (Glacier Mass Balance Intercomparison Exercise) study is the result of a large-scale effort by the scientific community, which collected, homogenized and combined data on glacier mass changes from in situ and remote sensing observationsFour main observation methods were used:

• Glaciological measurements: Direct measurements of ice accumulation and ablation on approximately 500 unevenly distributed glaciers.
• Digital Elevation Modeling (DEM): Repeated mapping of glacier surfaces and calculation of elevation differences to determine volume changes.
• Altimetry: Measuring elevation changes along linear routes using laser and radar altimeters.
• Gravimetry: Estimating regional changes in glacier mass by measuring changes in the Earth's gravitational field using satellites.

Implications for the future:

The study confirms that Global warming caused by human activity is having a direct and serious impact on glaciers around the world.Melting glaciers contribute to rising sea levels, which threatens coastal communities and ecosystems. In addition, glacier loss can lead to water shortages in regions that depend on them as a source of freshwater.

The study authors emphasize that Based on current trends, we can expect continued and perhaps accelerating glacier loss by the end of this century.They urge urgent and concrete action to reduce greenhouse gas emissions and limit warming to mitigate the impact of melting glaciers on local geohazards, regional freshwater availability, and global sea levels.

Comparison with previous IPCC estimates:

The GlaMBIE results generally confirm the trends in glacier mass loss reported in the IPCC reports. The global estimates of glacier mass change are 4 %, 9 % and 8 % less negative than those in the IPCC Fifth Assessment Report (AR5), the Special Report on Oceans and Lands under Climate Change (SROCC) and AR6, respectively. However, the authors emphasize that their study provides more detailed and precise estimates due to its more extensive data collection and advanced methodology.

Challenges and future steps:

The study also highlights the challenges associated with measuring and modeling glacier mass changes, including differences between different observational methods and a lack of understanding of volume-to-mass conversion over short time periods. Further research and intercomparison at higher spatial and temporal resolutions are needed to improve the accuracy of estimates and reduce uncertainties.

It is also important to continue monitoring glaciers using a variety of methods and to improve models to better understand their dynamics and predict their future evolution. Also, estimates of volume-to-mass conversion need to be improved, especially for short time periods. The new study provides compelling evidence of the accelerating melting of global glaciers and its potential impacts on rising sea levels and water availability. The study results underscore the urgency of taking action to reduce greenhouse gas emissions and limit global warming to mitigate the negative consequences of glacier melting. Spring

GlaMBIE Team, Michael Zemp, Livia Jacob,.. Study published in the journal Nature

Glossary of key terms

• Glaciological measurements: Direct measurements of accumulation and ablation on glaciers.
• DEM differencing: A method for determining changes in glacier surface elevation using digital terrain difference models.
• Altimetry: A measurement of the height of the Earth's surface from space, used to track changes in the height of glaciers.
• Gravimetry: A measurement of the Earth's gravitational field, which is used to estimate changes in the mass of glaciers.
• Gigatonne (Gt): A unit of mass equal to 10^12 kg (1 trillion kilograms).
• Specific mass change (m we): Mass change relative to the area of the glacier, expressed in meters of water equivalent.
• Ablation: The process of losing glacier mass through melting, sublimation, or the breaking off of glacier ice.
• Accumulation: The process of accumulating mass on a glacier, for example through snowfall.
• Hydrological cycle: The water cycle in nature, which includes evaporation, precipitation, and runoff.
• IPCC (Intergovernmental Panel on Climate Change): The Intergovernmental Panel on Climate Change, which assesses scientific knowledge about climate change.
• GlaMBIE (Glacier Mass Balance Intercomparison Exercise): A project that aims to compare and combine estimates of glacier mass changes from different observational methods.
• Karakoram anomaly: An unusual phenomenon in the Karakoram Mountains, where some glaciers showed an increase or stability in mass at a time when most glaciers in the world were retreating, but are now retreating.
• Sea level equivalent: The volume of water that will be created from melting ice, expressed as a rise in global sea level.
• Mass balance: The difference between accumulation and ablation.
• Marine-terminating glaciers: Glaciers that end in the sea and lose mass through the breaking off of ice floes.
• Hypsometry: Measurement and study of the height distribution of glacier surfaces.