Dr. Derrick Lampkin, of NASA HQ will give a virtual lecture as part of the CLASP Seminar Series. Please join us!

This is a Zoom virtual event.
Zoom link: https://umich.zoom.us/j/91331459775?pwd=eVA3Z1NhcjR0NDR2cmQzSWdrc1FWZz09
Meeting ID: 913 3145 9775
Passcode: 421507

TITLE:
Greenland’s Shear Margins in Warming Climate: A Summary of Recent Work

ABSTRACT:
The Greenland Ice Sheet has experienced unprecedented changes in the couple decades resulting from regional warming resulting in enhanced surface melting. The increase in melting has activated a dynamic surface hydrologic system contributing to significant mass loss. Surface melt runoff contributes directly to Greenland’s mass loss as well as infiltration which impact ice dynamics and mass discharge. The ice sheet has a few critical bounding forces that can influence the rate of mass loss which includes the loss of ice shelves/tongues, enhanced calving at marine-terminating outlet glaciers, and an evolving basal hydrologic system due to infiltration of surface melt. In particular, the impact of surface melt water on ice dynamics via supraglacial lake drainage and runoff has been well documented. Little attention has been focused on direct injection of surface melt water into the shear margins of fast flowing, marine-terminating outlet glaciers, which are a critical control on mass flux. Our initial work was the first to characterize water-filled crevasse ponds within the shear margins of Jakobshavn Isbræ and assess the volume of infiltrated melt water potentially reaching the bed. In the intervening years since this seminal work, we have utilized satellite observations and numerical models to decode the impact of hydrologic shear weakening due to melt water injection from these structures with implications for the evolution of Greenland’s other marine-terminating outlet glaciers under a warming climate.

We have constrained the theoretical impact of hydrologic shear weakening on extra-marginal ice flow using diagnostic models and provide projections for flow enhancement under future warming scenarios. For select seasons, we assessed relationships between extra-marginal, summer-time ice velocities and drainage of water-filled crevasses. We are starting to understand factors that drive how these crevasse systems fill and drain. We have characterized the spatial and temporal variability of melt extent over a 16 year period and assess the temporal changes in hydrologic state (filled vs. drained). Lastly, we explore implications for how not only water-filled shear ponds but other mechanisms such as rheological modification influence the dynamics of marine-terminating outlet glacier systems. Under future regional warming scenarios, we expect for mass discharge from Greenland’s outlet glaciers to be enhanced by perturbations to shear margins of these glacial systems.