Terrestrial Glaciers and Ice Sheets


We seek to understand the current state and dynamics of glaciers and ice sheets on Earth in order better predict their response to a warming climate.  Our primary method of study is airborne radar sounding, but we are engaged in a variety of projects using multiple methods.  

Our focus recently has been on Alaskan glaciers, since they are changing rapidly and are the largest non-polar source of global sea-level rise.  We have undertaken many field campaigns since 2015 as part of NASA's Operation IceBridge, attempting to map ice thickness for all of the major glacier systems in Alaska in conjunction with repeat scanning lidar measurements of the glacier surfaces.  In order to accomplish this, we have developed the most advanced low-frequency (long wavelength) airborne radar sounder operating today.  The  glaciers of Alaska have warm ice, heavy crevassing and a high water content, all of which make radar sounding more challenging than for polar ice sheets.  

We have also started a new project on Malaspina Glacier in southeast Alaska, the world's largest piedmont glacier, that combines surface, airborne, and satellite observations in support of a modeling effort to predict how Malaspina will respond to encroaching ocean waters due to rapidly degrading ice-cored forelands.  

GoPro time lapse of a flight from Yakutat, AK over Malaspina Glacier and past Mt. Saint Elias

While ice loss rates are higher for glaciers in Alaska than anywhere else in the world (Hugonnet et al., 2021), regional ice thickness remains poorly constrained. As part of NASA's Operation IceBridge, the TAPIR group has acquired airborne radar sounding data data over glaciers throughout Alaska since 2015 in conjunction with collaborators from the University of Alaska, Fairbanks. This work has involved the development of an evolution of radar systems, with the latest being the Arizona Radio Echo Sounder (ARES), a chirped system operating at a center frequency of either 2.5 or 5 MHz. Following radar data processing, radar profiles are investigated for the presence of glacier bed returns. If bed returns are detected, they are manually digitized allowing for measurements of ice thickness.


Example radar sounding profile across Malaspina Glacier, AK. Glacier surface in blue, glacier bed in orange.


Measurements of ice thickness for Malaspina Glacier, AK.

Tober et al., 2022


Interpolated ice thickness for Malaspina Glacier, AK.

Tober et al., 2022


  • Operation IceBridge (NASA Award: NNX16AC32G; Jack Holt, CO-I)
  • A New Regional View of Alaskan Glaciers: Bed Elevation, Ice Thickness, and Flux (NASA FINESST; Future Investigator, Brandon Tober)


  • The demise of the world's largest piedmont glacier (NSF Award: 1929566; Jack Holt, CO-I)