The Cryosphere

Changes in the cryosphere, especially the major ice sheets on Greenland and Antarctica, represent another key research area in the physical climate system. Comprehensive, simultaneous, and sustained measurements of ice sheet mass and volume changes and ice velocities are needed, along with measurements of ice thickness and bed conditions, both to quantify the current contributions of ice sheets to sea level rise (discussed below) and to constrain and inform ice sheet model development. These measurements, which include satellite, aircraft, and in situ observations, need to overlap for several decades in order to enable the unambiguous isolation of ice melt, ice dynamics, snow accumulation, and thermal expansion. Equally important are investments in improving ice sheet process models that capture ice dynamics as well as ice-ocean and ice-bed interactions. Efforts are already underway to improve modeling capabilities in these critical areas, but fully coupled ice-ocean-land models will ultimately be needed to reliably assess ice sheet stability, and considerable work remains to develop and validate such models. Glaciers and ice caps outside Greenland and Antarctica are also expected to remain significant contributors to sea level rise in the near term, so observations and analysis of these systems remain critical for understanding decadal and century-scale sea level rise. Finally, additional paleoclimate data from ice cores, corals, and ocean sediments would be valuable for testing models and improving our understanding of the impacts of sea level rise.

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