ISMASS Expert Group
The Expert Group on Ice Sheet Mass Balance and Sea Level (ISMASS) is co-sponsored by the WCRP Climate and Cryosphere Project (CliC), the Scientific Committee on Antarctic Research (SCAR), the International Arctic Science Committee (IASC). The goals of ISMASS are to promote research on the estimation of the mass balance of ice sheets and their contribution to sea level, to facilitate the coordination among different international efforts focused on this field of research, to propose directions for future research, to integrate observations and modelling efforts, and promote distribution and archiving of the corresponding data, to attract a new generation of scientists into this field of research, to contribute to the diffusion of the current scientific knowledge and the main achievements to society and policy makers. Further details on the goals of ISMASS can be found in the Terms of Reference.
Current ISMASS chair: Heiko Goelzer
The Importance of Estimating Ice Sheet Mass Balance
The mass balance of an 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 the ice sheet is losing mass, and, for grounded portions of ice sheets, most of this mass loss directly contributes to sea level rise. The melting of floating ice shelves and ice tongues does not contribute much directly to sea level rise but may influence the dynamic response of the connected ice sheet inland. This is one of the reasons why it is important, under a warming climate, to have accurate estimates of the mass balance of 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 older data), the dating requires modelling the ice sheet dynamics.
For the large ice sheets of Antarctica and Greenland, the estimation of present mass balance is possible using remote sensing (satellite or airborne) techniques, though these need to be calibrated and validated against measurements done on the ice sheet 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 ice sheets. These models have to be integrated with climate models that provide the information on accumulation and melting at the glacier surface and the interaction between the ice sheets and the ocean.