Ice dynamics

Ice loss from the polar ice sheets is the largest anticipated contribution to 21st century global mean sea level rise. A fundamental control on the rate of ice loss is how fast ice flows from ice sheet interiors out to the edges. In the interior of the Greenland Ice Sheet, ice flow responds to liquid water (“runoff”) input, which affects how the ice slides over the bedrock beneath. At ocean-terminating “outlet glaciers” around the edges of Greenland, ice flows into the ocean with speed that varies by season. That strong seasonal variation makes it more difficult to tell to what extent liquid water input is affecting the flow speed. Identifying the relative strength of ocean-driven versus melt-driven ice flow variations is essential for the computer models used to forecast future ice loss. It has been difficult to assess those factors in a consistent way because they operate over multiple time scales, thus requiring different methods of observation that could not be directly compared.

I have used flexible time series analysis methods to show that a large glacier in East Greenland responds to ocean and atmospheric forcing at different time scales. I am now lead PI on a National Science Foundation grant that will collect new field observations in West Greenland, analyze them in a multivariate statistical framework with satellite observations, and extend our analyses to other settings with idealized numerical modeling in Elmer/Ice.

Students

Amy Jenson (UAF), Aiden Pape (Middlebury)

Collaborators

Martin Truffer (UAF), Jason Amundson (U. Alaska Southeast), Denis Felikson (NASA Goddard), Leigh Stearns (U. Kansas), Brent Minchew (MIT), Bryan Riel (Zhejiang U.)

Publications

Ultee, L., Felikson, D., Minchew, B., Stearns, L. A., and Riel, B. (2022). “Helheim Glacier ice velocity variability responds to runoff and terminus position change at different timescales.” Nature Communications doi: 10.1038/s41467-022-33292-y .