Project Summary

Greenland Ice Sheet Freshwater Discharge

Collaborative Research: A Synthesis of Rapid Meltwater and Ice Discharge Changes: Large Forcings from the Ice with Impacts on Global Sea Level and North Atlantic Freshwater Budgets

Lead PIs:
  • Mark Fahnestock, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire
  • Richard Alley, Department of Geosciences and Earth and Environmental Systems Institute, Pennsylvania State University
  • Jason Box, Department of Geography, Ohio State University
  • Sarah Das, Department of Geology and Geophysics, Woods Hole Oceanographic Institution
  • Ian Joughin, Polar Science Center, University of Washington
  • Martin Truffer, Geophysical Institute, University of Alaska Fairbanks

Freshwater discharge from the Greenland ice sheet has a direct and immediate effect on global sea level, has the potential to impact global climate by perturbing nearby sensitive regions of oceanic deep-water formation, and is an important but as yet poorly quantified part of the pan-Arctic water balance.

The investigators will synthesize a range of extant data sets using numerous methods. Remote sensing and atmospheric modeling calibrated by surface data accurately reveal a spatially resolved history of surface melting on Greenland over decades, and coastal weather stations extend observations to more than a century. Sophisticated transfer techniques, including nonlinear approaches, will be used to downscale from these instrumental data to specific ice-core records of melt, learning how the widespread signal is archived. The derived transfer functions, the centuries-long ice-core records, and the century-length coastal-station records then will allow upscaling to determine meltwater variability over longer times than now available. Remotely sensed changes in ice shelves/tongues and outlet-glacier flow speeds will be combined with the contemporaneous histories of surface melting, and analyzed using diagnostic ice-flow modeling incorporating longitudinal stresses to learn how meltwater variability and ice shelf changes force ice-flow variability. If successful diagnosis is achieved, then the longer melt history from the ice-cores can be used to estimate the ice-flow variability over the same interval; the relations between ice-flow and melt changes also can be used prognostically in assessing future changes in the ice sheet affecting freshwater fluxes.