Team Geophysics

We apply seismic reflection and refraction methods as well as passive imaging techniques that have been applied successfully in high-arctic environments to image the interior and subglacial properties of Lemon Creek Glacier, part of the Juneau Icefield in Southeast Alaska. Our work serves to elucidate the firn and ice structure, the rheology of the glacier, as well as the basal properties of the glacier. 
 
Dataset:
During June 2017, we acquired a 1-km-long seismic reflection and refraction survey on Lemon Creek Glacier, a 5.7-km-long subarctic mountain glacier in the Juneau Icefield of Southeast Alaska. We used 51 5-Hz Z-Land Fairfield nodal seismometers recording at 1000 Hz and a Betsy Seismic Gun source with 400-grain, 8-gauge blanks. Fairfield nodal seismometers are small, highly-portable sensors that may rapidly be deployed in dense networks in challenging environments. The seismic survey was located in upper portion of the glacier within the accumulation zone, oriented parallel to the flow direction, and approximately followed the glacier’s center line.  In this survey, the receivers were initially spaced at 20-m, and shots were fired between them at 20-m spacing. We fired multiple shots near the ends of the line to allow stacking to enhance the signal. After we recorded the initial active-source survey, we re-deployed the nodes in a regional array across the upper part of the glacier at ~350-m spacing. In mid-July, we fired additional shots adjacent to ~25 of those nodes to provide further constraints on ice thickness.
 
Societal impact:
The use of seismology as a means to study glacier dynamics has rapidly expanded in recent years as we seek to better understand the present and future behavior of glaciers in a rapidly changing climate. While smaller in mass than their Antarctic or Greenlandic cousins, sub-arctic mountain glaciers may be particularly vulnerable to rapid changes in climate, making them a worthy target of study.