Ground-Penetrating Radar Ice Thickness Survey of Mathis, Llewellyn, and  Tulsequah Glaciers on the Juneau Icefield, Alaska and Canada

AGU Abstract: In this study, we investigated the bed topography and ice thickness of Mathis, Llewellyn, and Tulsequah Glaciers. Mathis is a major tributary to one of Southeast Alaska’s largest and deepest temperate glaciers, Taku Glacier. Taku Glacier recently ceased a long term advance likely due to a decreasing accumulation area ratio, making it an object of concern for a potential future retreat. Measurements of ice thickness and estimated volume, with mass balance and ice flow velocity records collected annually across the Juneau Icefield by the Juneau Icefield Research Program, will provide crucial data for modeling current and future advance or retreat. However, measuring deep temperate valley glacier ice is notoriously difficult due to high attenuation rates and valley wall clutter. We used a 1.5 MHz ground-penetrating-radar (GPR) dipole antenna set with a 2.5 kV Kentech transmitter towed by a snow machine to measure ice thickness over 80km of glacier terrain. Data included a centerline profile of Llewellyn and Mathis Glacier and a 4 km by 4 km grid collected at the triple ice divide between Mathis, Tulsequah, and Llewellyn Glaciers between July 20-28th, 2018. GPR survey revealed smooth valley wall reflections on glacier cross-sections and ice thicknesses over 900 meters depth near the center of the Mathis Glacier. Continued monitoring of the Taku Glacier is crucial to understand how Mathis, Llewellyn, and Tulsequah glaciers will react to further climate change impacts. Our results, in conjunction with other available mass balance and velocity datasets, provide information for the robust modeling of this system. 

Marisa Borreggine, Gryphen Goss, Isabelle Henzmann, 

Cody Barnett, Roberta Miller, Seth Campbell