Evolving environmental and geometric controls on Columbia Glacier’s continued retreat

Journal of Geophysical Research- Earth Surface
By: , and 

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Abstract

Geometry strongly controls the dynamic behavior of marine‐terminating (tidewater) glaciers, significantly influencing advance and retreat cycles independent of climate. Yet the recent, nearly ubiquitous retreat of tidewater glaciers suggests that changes in atmospheric and oceanic forcing may also drive dynamic change. To isolate the influence of geometry on tidewater glacier dynamics, we analyzed detailed observational time series from 2012 to 2016 for two tidewater glaciers with shared dynamic histories and environmental forcing: Columbia Glacier and its former tributary (Post Glacier) in southcentral Alaska. We find that although terminus retreat has driven decadal‐scale changes in dynamics of the Columbia‐Post system, environmental factors contribute to short‐term (i.e., seasonal) dynamic variability. In particular, analysis of force balance time series indicates that observed variations in speed result from seasonal changes to the subglacial hydrologic system and associated changes in basal drag. Variations in terminus position only drive noticeable speed change when the terminus retreats from regions of relatively high basal drag. In agreement with long‐term analyses of Columbia Glacier, we find that terminus geometry can perturb the timing of seasonal ice flow patterns. Specifically, our data support the idea that retreat of a glacier terminus into deeper water is accompanied by a shift in the primary control on frontal ablation. Although our analysis focuses on two Alaskan glaciers, our data suggest that changes in the relative importance of surface meltwater and buoyancy effects on submarine melting and/or calving may manifest as a shift in terminus change seasonality and offer a mechanism to identify frontal ablation controls.

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Publication type Article
Publication Subtype Journal Article
Title Evolving environmental and geometric controls on Columbia Glacier’s continued retreat
Series title Journal of Geophysical Research- Earth Surface
DOI 10.1029/2017JF004541
Volume 123
Issue 7
Year Published 2018
Language English
Publisher Wiley
Contributing office(s) Alaska Science Center
Description 18 p.
First page 1528
Last page 1545
Country United States
State Alaska
Other Geospatial Columbia Glacier
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