Greenland Flow Dynamics: (De)coding Process Understanding

Thursday, 17 December 2015: 10:20
3007 (Moscone West)
Byron R Parizek1, Richard B Alley2, Sridhar Anandakrishnan3, Patrick J Applegate4, Knut A Christianson5, Timothy H Dixon6, David M Holland5, Nicholas Holschuh7, Klaus Keller2, Stephen J Koellner1, Derrick Julius Lampkin8, Atsuhiro Muto2, Robert Nicholas2, Nathan Thomas Stevens2, Denis Voytenko5 and Ryan T Walker9, (1)Pennsylvania State University, DuBois, PA, United States, (2)Pennsylvania State University Main Campus, University Park, PA, United States, (3)Pennsylvania State University, Department of Geosciences, University Park, PA, United States, (4)Penn State University, University Park, PA, United States, (5)New York University, New York, NY, United States, (6)University of South Florida Tampa, Tampa, FL, United States, (7)Pennsylvania State University Main Campus, Geosciences, University Park, PA, United States, (8)University of Maryland College Park, College Park, MD, United States, (9)University of Maryland, Greenbelt, MD, United States
Extensive modeling informed by the growing body of observational data yields important insights to the controlling processes operating across a range of spatiotemporal scales that have influenced the dynamic variability of the Greenland ice sheet. Pressurized basal lubrication enhances ice flow. This lubricating water is largely produced by basal and/or surface melt. For the North East Greenland Ice Stream, elevated geothermal heat flux (GHF) near its onset helps initiate the streaming flow. We suggest that the elevated GHF is likely caused by melt production and migration due to cyclical loading of the lithosphere over glacial timescales. On sub-seasonal timescales, surface meltwater production and transmission to the subglacial environment can enhance flow for pressurized, distributed hydraulic systems and diminish regional sliding for lower-pressure, channelized systems. However, in a warming climate, this lubricating source occurs across an expanding ablation zone, possibly softening shear margins and triggering basal sliding over previously frozen areas. Yet, the existence of active englacial conduits can lead to a plumbing network that helps preserve ice tongues and limit the loss of important buttressing of outlet glacier flow. Ocean forcing has been implicated in the variability of outlet glacier speeds around the periphery of Greenland. The extent and timescale over which those marginal changes influence inland flow depends on the basal rheology that, on a local scale, also influences the concentration of englacial stresses. Detailed observations of a calving event on Helheim Glacier have helped constrain diagnostic simulations of the pre- and post-calving stress states conducted in hopes of informing improved calving relationships. Furthermore, warm-water-mass variability within Irminger/Atlantic Waters off Greenland may play an important role in the monthly modulation of outlet glacier flow speeds, as has been observed for an ice stream draining into Pine Island Bay. However, for large warming, the magnitude and rate of surface warming become increasingly important as the combination of negative surface mass balance and inland drawdown dominate system response. Within this overview, key results from idealized simulations addressing each of these processes will be highlighted.