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Terminus dynamics at an advancing glacier: Taku Glacier, Alaska

journal contribution
posted on 2023-05-17, 15:25 authored by Truffer, M, Motyka, RJ, Hekkers, M, Howat, IM, Matt KingMatt King
Taku Glacier, Alaska, USA, is currently in the advance stage of the tidewater glacier cycle. We investigated the near-terminus dynamics by measuring surface velocities, surface elevation changes, ice thickness and ablation. Velocities vary on sub-daily, diurnal, seasonal and interannual timescales. Flowline modeling shows that the modeled surface velocities are sensitive to changes in till yield strength and thus effective basal pressures. The glacier bed deepens in the up-glacier direction and this imposes a minimum subglacial water pressure necessary for water to drain along the bed. In a simple model we impose water-pressure gradients based on phreatic surfaces of constant slopes to simulate the wintersummer transitions. This proves sufficient to explain an observed early-season switch from compressional to block flow. Velocities also vary between years. Changing basal conditions can result in lower horizontal velocities, which decrease the ice supply to the terminus and result in temporary surface lowering. But a decrease in ice flux to the terminus must lead to ice storage further upstream, and that ice mass will eventually reach the terminus. This can explain the observed episodic nature of terminus advance.

History

Publication title

Journal of Glaciology

Volume

55

Issue

194

Pagination

1052-1060

ISSN

0022-1430

Department/School

School of Geography, Planning and Spatial Sciences

Repository Status

  • Restricted

Socio-economic Objectives

Expanding knowledge in the earth sciences