Microtopographic control on the ground thermal regime in ice wedge polygons
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Published:2018-06-11
Issue:6
Volume:12
Page:1957-1968
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ISSN:1994-0424
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Container-title:The Cryosphere
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language:en
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Short-container-title:The Cryosphere
Author:
Abolt Charles J.ORCID, Young Michael H.ORCID, Atchley Adam L.ORCID, Harp Dylan R.ORCID
Abstract
Abstract. The goal of this research is to constrain the influence of ice
wedge polygon microtopography on near-surface ground temperatures. Ice wedge
polygon microtopography is prone to rapid deformation in a changing climate,
and cracking in the ice wedge depends on thermal conditions at the top of the
permafrost; therefore, feedbacks between microtopography and ground
temperature can shed light on the potential for future ice wedge cracking in
the Arctic. We first report on a year of sub-daily ground temperature
observations at 5 depths and 9 locations throughout a cluster of low-centered
polygons near Prudhoe Bay, Alaska, and demonstrate that the rims become the
coldest zone of the polygon during winter, due to thinner snowpack. We then
calibrate a polygon-scale numerical model of coupled thermal and hydrologic
processes against this dataset, achieving an RMSE of less than
1.1 ∘C between observed and simulated ground temperature. Finally,
we conduct a sensitivity analysis of the model by systematically manipulating
the height of the rims and the depth of the troughs and tracking the effects
on ice wedge temperature. The results indicate that winter temperatures in
the ice wedge are sensitive to both rim height and trough depth, but more
sensitive to rim height. Rims act as preferential outlets of subsurface heat;
increasing rim size decreases winter temperatures in the ice wedge. Deeper
troughs lead to increased snow entrapment, promoting insulation of the ice
wedge. The potential for ice wedge cracking is therefore reduced if rims are
destroyed or if troughs subside, due to warmer conditions in the ice wedge.
These findings can help explain the origins of secondary ice wedges in modern
and ancient polygons. The findings also imply that the potential for
re-establishing rims in modern thermokarst-affected terrain will be limited
by reduced cracking activity in the ice wedges, even if regional air
temperatures stabilize.
Publisher
Copernicus GmbH
Subject
Earth-Surface Processes,Water Science and Technology
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