Rapid reconfiguration of the Greenland ice sheet margin

Abstract:

The rapid acceleration of Greenland Ice Sheet mass loss over, particularly the last two decades, is well documented. However, limits in early remote sensing restricted the details with which we could examine local changes on an ice-sheet-wide scale, particularly in areas of slow motion, along shear margins and complex coastal terrain. We explore the local character of rapid contemporary change marine-terminating glaciers using satellite-derived ice sheet surface velocities, glacier terminus advance/retreat history, and surface elevation-change data from the 1980s to the present. Widespread glacier terminus retreat is a strong and more consistent climate response indicator than velocity change, but local changes in velocity are critical indicators of rapid ice sheet reconfiguration. Ice thickness changes related to changing ice dynamics often provide the first evidence of processes that initiate outlet glacier retreats and mass loss, such as the development of sub-ice shelf cavities and subglacial hydrology changes. Reconfiguration is observed locally as narrowing zones of fast-flow, ice flow rerouting, shear margin migration, and likely glacier outlet abandonment. These patterns are apparent in all ice sheet sectors and observable from space-borne instruments. The rapid reconfiguration now well underway in Greenland has wide-ranging implications, including expected changes in subglacial hydrology, ice discharge, freshwater flux to the ocean, and transport of nutrients and sediment. Lacking detailed observations of earlier deglaciations and current limits on ice-sheet model capabilities, the expanding details of these combined observational records may provide a valuable analog for studying past ice sheet dynamics and projecting future ice loss.