Turning Greenland Upside Down: A Coupled Observational-modeling Approach to Understanding the Puzzling Response of Ice Sheet Flow to Meltwater Variability

Sarah Das, Geology & Geophysics
Mark Behn, Geology & Geophysics



Greenland is warming up and slowing down.  This paradox is one of the most pressing unsolved problems in glaciology, and at the most basic level limits our ability to understand how the Greenland ice sheet responds to climate variability.  This in turn hinders our understanding of the role that Greenland ice mass loss plays in contributing to global sea level rise, freshwater and nutrient fluxes to the ocean, and changes in ocean circulation.  It also highlights the fact that despite much progress in the past decade by our group and many others, we still lack a fundamental physical understanding of the role that melt-water (generated at the surface) plays in ice sheet dynamics (largely controlled by processes at the bed).  This understanding is critical to predicting future ice sheet behavior under warming scenarios, which project: a lengthening of the melt season; increasing melt intensity (and perhaps variability); and a widening of the melt zone upslope across thicker grounded ice whose bed is presently isolated from surface meltwater fluxes.
Here we propose a timely, compelling, and distinct project that brings together glaciology, geodynamics and applied mathematics to peer under the ice sheet (subglacial), guided by observations made at the surface (supraglacial).  We will combine a state-of-the-art subglacial hydrological model (Hewitt, 2013) with a unique ~decadal-length set of observations of ice sheet surface motion and meltwater runoff from climate reanalyses (Stevens et al., 2016).  By ‘turning Greenland upside down’ we will provide an unprecedented, high-resolution, view of the evolution of the subglacial hydrological system in response to time-varying surface meltwater input over recent years to decades.