Dr. Colgan’s Research Lecture


Dr. William Colgan
Geological Survey of Denmark and Greenland (GEUS)
Friday, April 11, 2014
11:00 a.m.
Room 3120 Herzberg

Glacier hydrology in a changing climate

I will survey my three-pronged approach to studying glacier-climate interactions: field work, remote sensing and numerical modeling.

First, I will present an in situ water budget from a small supra-glacial catchment in West Greenland, in which the search for a missing "sink" forced us to carefully reconsider the role of crevasses in ice sheet hydrology. Linear reservoir theory suggests that crevasses are less efficient in transmitting meltwater pulses to ice sheet bed than "moulins" (near vertical conduits through the ice sheet). As basal sliding is enhanced by meltwater pulses pressurizing the ice-bed interface, changes in crevasse extent are associated with changes in basal sliding sensitivity.

Second, I will present a decadal survey of supra-glacial lakes in West Greenland. Catastrophic lake drainage events are capable of introducing large quantities of liquid water to the ice-bed interface via hydrofracture. Using an object-oriented algorithm to extract hundreds of lake area time series from thousands of MODIS images indicates that catastrophic lake drainage events occur more frequently, as well as at higher elevations, in relatively high melt years. This suggests that sub-glacial water, and associated sub-glacial latent heat, will become more available under projected climate change.

Third, I will present 3D ice flow modelling that explores a thermal collapse of the Greenland ice sheet via "cryo-hydrologic warming" (the transfer of latent heat from refreezing meltwater to surrounding glacier ice). As the effective viscosity of ice is non-linearly dependent on ice temperature, rapid changes in ice sheet temperature can translate into rapid changes in ice sheet form and flow. A first order assessment suggests that the latent heat anomalies associated with projected surface mass balance are sufficient to warm the deepest 15% of the ice sheet, where the majority of shear occurs, to the pressure-melting-point over the next four centuries.

I will conclude my talk by introducing my teaching interests, as well as outlining potential objective- and hypothesis-driven projects in which I am interested.