Date of Award

Spring 1-1-2018

Document Type


Degree Name

Doctor of Philosophy (PhD)

First Advisor

Waleed Abdalati

Second Advisor

Theodore Scambos

Third Advisor

W Tad Pfeffer

Fourth Advisor

Barbara Buttenfield

Fifth Advisor

Konrad Steffen


Recent increases in Greenland’s glacial melt have accelerated runoff and become Greenland’s dominant mechanism of ice loss. More meltwater is being generated in the ice sheet’s lower accumulation zone, which has begun to anneal ice lenses found within the porous firn and form continuous low-permeability ice slabs (LPISs). LPISs are layers of ice meters thick that inhibit water percolating beneath them, extend horizontally for tens of kilometers, and can cause runoff from regions where water previously refroze. LPISs form on decadal timescales and have the potential to quickly increase the extent of Greenland’s runoff zone. I present multiple lines of evidence that show LPISs have already increased runoff in recent above-average melt summers, including the record-breaking 2012 summer in Greenland. I use NASA’s Operation IceBridge radar to map LPISs across Greenland’s ice sheet and peripheral glaciers and show that LPISs already cover approximately 5% of Greenland’s total glaciated area. I combine radar observations with regional climate models to show that Greenland’s LPISs will likely be 130-850% more extensive by 2100 depending upon 21st century CO2 emissions scenarios. LPISs under a high emissions future span more than a 250% greater area in 2100 than under moderate emissions, suggesting that ongoing emissions this century play a vital role in controlling melt and determining the size of Greenland’s runoff zone.