Ice shelves cover more than half of the nearly 18,000 km of Antarctica’s coastline. These floating ice masses can experience melt from below if ocean waters are warm enough. Many ice shelves around the continent exhibit rising basal melt rates. Since ice shelves already float on the sea, their melting does not directly contribute to sea levels. However, basal melt will affect the buttressing force these ice shelves exert on inland ice lying behind them, which is diminished as they lose mass. Since ice shelves thus stabilize huge volumes of ice which are currently above sea level, understanding how their melting will affect these ice masses is crucial.
Jurgen Determann and his colleagues use a thermomechanical ice-flow model to study how the Antarctic ice sheet would respond to different melting scenarios up to 1000 years into the future. A moderate basal melt rate, sustained over 1,000 years, would lead to significant mass loss; if mass loss were then to cease, the system would take 5,000 years to return to the initial state. More realistic, higher melt rates have even more devastating effects and reduce total ice volume by up to a quarter. They find that a change from ice-sheet to ice-shelf flow, where ice loses contact with the ground, causes faster mass loss than vice versa, so any mass loss would take much longer to be reversed.
This modeling effort, while containing many simplifications, highlights the importance of considering oceanic effects in the future evolution of ice sheets and of understanding ice-shelf melt and its causes.
Ice2sea Work Package: WP4.3
Publication: Determann, J., Thoma, M., Grosfeld, K., Massmann, S. (2012) Impact of ice-shelf basal melting on inland ice-sheet thickness: a model study. Annals of Glaciology, 53 (60), 129-135.