Melting ice sheets in Greenland and the Antarctic as well as ice melt from glaciers all over the world are causing sea levels to rise. New data and analysis show that land-based glaciers outside of the main ice sheets in Antarctica and Greenland have lost more than 9,000 billion tons of ice since 1961, raising sea levels by 27 millimeters.
A new study detailing the world’s melting glaciers and their contribution to rising sea levels has been published by an international research team under the lead of the University of Zürich.
According to the study, glaciers have lost more than 9,000 billion tons (that is 9 625 000 000 000 tons) of ice between 1961 and 2016, which has resulted in global sea levels increasing by 27 millimeters in this period. The largest contributors were glaciers in Alaska, followed by the melting ice fields in Patagonia and glaciers in the Arctic regions.
Glaciers in the European Alps, the Caucasus and New Zealand were also subject to significant ice loss; however, due to their relatively small glacierized areas they played only a minor role when it comes to the rising global sea levels.
For the new study, the team combined glaciological field observations with geodetic satellite measurements. The latter digitally measure the surface of the Earth, providing data on ice thickness changes at different points in time. The researchers were thus able to reconstruct changes in the ice thickness of more than 19,000 glaciers worldwide.
The reconstruction was also possible thanks to the comprehensive database compiled by the World Glacier Monitoring Service (WGMS), from its worldwide network of observers, to which the researchers added their own satellite analyses.
Robert McNabb, a Postdoctoral Fellow with the Department of Geosciences at University of Oslo, who has contributed many of the new geodetic measurements to the study, explains:
“The combination of the new satellite observations, along with glaciogical measurements from the WGMS database, enables us to estimate the amount of ice lost each year from glaciers and ice caps around the world since the mid-20th century. The field measurements give us the annual fluctuations, while the satellite data gives us the longer-term trends over large areas.”
335 billion tons of ice lost each year
The global mass loss of glacier ice has increased significantly in the last 30 years and currently amounts to 335 billion tons of lost ice each year.
This corresponds to an increase in sea levels of almost 1 millimeter per year.
“Globally, we lose about the total volume of ice stored in all of Norway and Sweden, each year,” says glaciologist McNabb.
The melted ice of glaciers therefore accounts for 25 to 30 percent of the current increase in global sea levels. This ice loss of all glaciers roughly corresponds to the mass loss of Greenland’s Ice Sheet, and clearly exceeds that of the Antarctic.
The present study was carried out under the lead of the University of Zürich, Switzerland, in collaboration with an international team of glaciologists from several institutions around the World:
ETH Zürich, CH, University of Fribourg, CH, Université Grenoble Alpes, FR, University of Oslo, NO, Queen’s University, Kingston, CA, University of Innsbruck, AT, Institute of Geography, Moscow, RU, and Trent University, Peterborough, CA.
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Zemp, M., Huss, M., Thibert, E., Eckert, N., McNabb, R., Huber, J., Barandun, M., Machguth, H., Nussbaumer, S.U., Gärtner-Roer, I., Thomson, L., Paul, F., Maussion, F., Kutuzov, S., and Cogley, J.G. (2019): Global glacier mass changes and their contributions to sea-level rise from 1961 to 2016. Nature, http://dx.doi.org/10.1038/s41586-019-1071-0
Further information about World Glacier Monitoring Service - WGMS
The study was supported by:
– Federal Office of Meteorology and Climatology MeteoSwiss within the framework of GCOS Switzerland, Cryospheric Commission of the Swiss Academy of Science, Irstea Grenoble as part of LabEx OSUG@2020; – Copernicus Climate Change Service (C3S) implemented by ECMWF on behalf of the European Commission; – ESA projects Glaciers_cci (4000109873/14/I-NB) and – Sea level closure CCI (4000119910/17/I-NB).