Abstract:

Around the periphery of the Greenland ice sheet, Global Navigation Satellite System (GNSS) stations record uplift that reflects Earth’s response to past and recent unloading of ice mass. On the southeast coast, near the Kangerlussuaq glacier, GNSS stations show unusually rapid ground uplift exceeding 12 mm/yr. Current earth deformation models, which employ a layered Earth structure, cannot explain this rapid uplift. We find that 3D models that incorporate a “track” of weakened earth structure, consistent with the passage of Greenland over the Iceland plume, can predict the rapid uplift of southeast Greenland. This uplift is dominated by a viscous response that is amplified by the low viscosities of the hot plume track. Recent mass loss, occurring during the last millennium and especially within the past few decades, drives most of the uplift. Rapid uplift also occurred in this area following deglaciation at the end of the last ice age, but this uplift happened thousands of years ago and was recorded by geologic indicators of sea level drop. Regions of weakened mantle positioned below marine terminating glaciers may be especially important, because rapid uplift following ice mass loss can affect the future stability of entire ice catchment areas upstream. Such regions will become increasingly important in the near future as deglaciation accelerates.

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