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Ice Sheet Mass Balance and Sea Level (ISMASS)

The ISMASS group was formed orginally as a SCAR group, then became bipolar when cosponsored by IASC. Now it is also co-sponsored by the Climate and Cryosphere (CliC) project of WCRP.

The ISMASS website is maintained by CliC - visit the website.

Why measure the mass balance of the icesheets?

There is around 7 metres of potential sea-level rise locked up in the Greenland icesheets and 57 metres in the Antarctic Icesheets. 

The mass balance of a glacier or ice sheet is the net balance between the mass gained by snow deposition, and the loss of mass by melting (either at the glacier surface or under the floating ice shelves or ice tongues) and calving (production of icebergs). A negative mass balance means that a glacier is losing mass, and, for grounded glaciers and ice sheets, this mass loss directly contributes to sea level rise (the melting of floating ice shelves and ice tongues does not contribute to sea level rise, because of the lower density of ice as compared to water, which determines the floating portion of the ice). This is one of the reasons why it is important, under a warming climate, to have accurate estimates of the mass balance of glaciers and ice sheets.

How is the mass balance estimated?

Past mass balance rates can be estimated from ice core data, although the proper dating of the samples is challenging. For the deeper parts of the ice core (representing the older data), the dating requires modelling the ice sheet dynamics.

For the large ice sheets of Antarctica and Greenland, the estimate of present mass balance is only possible using remote sensing (satellite or airborne) techniques, though these need to be calibrated and validated against measurements done on the glacier surface.

For predicting future mass balance, under different scenarios of climate change, it is necessary to use models of the dynamics and thermal regime of the glaciers and ice sheets. These models have to be integrated with climate models (that provide the information on accumulation and melting at the glacier surface) and oceanic models (which provide the interaction between the ice sheets and the ocean).

The Expert Group on Ice Sheet Mass Balance and Sea Level (ISMASS) is co-sponsored by SCAR, the International Arctic Science Committee (IASC) and the Climate and Cryosphere Project of WCRP.

The goals of ISMASS are to promote the research on the estimation of the mass balance of ice sheets and its contribution to sea level, to facilitate the coordination among the different international efforts focused on this field of research, to propose directions for future research in this area, to integrate the observations and modelling efforts, as well as the distribution and archiving of the corresponding data, to attract a new generation of scientists into this field of research, and to contribute to the diffusion, to society and policy makers, of the current scientific knowledge and the main achievements in this field of science.

For further details visit the ISMASS website.

Terms of Reference

ISMASS was established in 1993 as a SCAR-tasked group on Antarctic mass balance and sea-level contribution, which has since become bipolar. ISMASS is international and interdisciplinary across the spectrum of relevant ice-sheet mass balance disciplines, and is a self-governing expert group sponsored by SCAR, IASC and CliC. ISMASS aims to:

  • Assess the status of research on interactions between ice sheets and the climate and Earth systems, and identify gaps in current understanding requiring process studies, sustained and targeted campaign-based observations and model development and experiments.
  • Serve SCAR, IASC, CliC, research sponsors and other organizations as a source of knowledge on ice-sheet mass balance and propose directions for future research in this area.
  • Facilitate and serve as a forum for the evaluation and promotion of scientific understanding of ice-sheet system models for both Antarctica and Greenland, in particular with respect to their contributions to global sea-level rise, and to make such information readily available to scientists, policymakers, and the wider public.
  • Keep track of the status of ice-sheet research carried out and sponsored by scientific organizations such as WGMS, GLIMS, IACS and IGS, and liaise with them to ensure that respective activities contribute as much as possible to the objectives of SCAR, IASC and CliC.
  • Promote collaboration between all disciplines (e.g. atmospheric, oceanographic, cryospheric, biogeochemical, solid earth and palaeoclimate sciences) that have an interest in interactions between ice sheets and climate, and on rapid response to modern ocean and atmosphere forcings.
  • Work in concert with relevant SCAR, IASC and CliC panels and other groups to integrate ice-sheet observations and modelling into corresponding global and regional activities, and ensure that our collective objectives are met and resources used most efficiently.
  • Work with appropriate agencies on the distribution and archiving of ice-sheet observations and model output.
  • Attract a new generation of scientists, via interaction with groups such as APECS, into the field of ice-sheet mass balance research.