Geothermal heat flow in Antarctica
Carolyn Branecky Begeman, Slawek Tulaczyk, Andy Fisher
Geothermal heat flux (GHF) is an important part of the heat budget of continental ice sheets; in some parts of the West Antarctic Ice Sheet GHF has as much influence on the pattern of slow- and fast-flowing ice as subglacial topography. The relative difficulty of measuring subglacial GHF, which requires direct access to the bed of the ice sheet, compared with measuring bed topography, which can be determined from airborne platforms, results in a low level of understanding of GHF in glaciated regions. We present a new GHF measurement from West Antarctica (WA) made through a borehole near the grounding zone of the Whillans Ice Stream, which flows into the Ross Sea. The measured GHF, 88 ± 7 mW m^-2, is relatively high compared to most continental values, but is consistent with previous regional estimates based on the geologic setting. Available GHF measurements and estimates from WA exhibit a greater degree of variability than continental GHF models used in ice sheet models. Given the significance of GHF for determining the pattern of slow- and fast-flowing ice, poor knowledge of GHF will negatively impact our ability to predict future ice sheet contributions to sea level rise. Begeman, C. B., Tulaczyk, S. M., & Fisher, A. T. (2017). Spatially Variable Geothermal Heat Flux in West Antarctica: Evidence and Implications. Geophysical Research Letters, 44. https://doi.org/10.1002/2017GL075579 An edited version of this paper was published by AGU. Copyright (2017) American Geophysical Union. Preprint available here. |
Measuring geothermal heat flowThis geothermal probe was designed by my collaborators at UCSC, especially Prof. Andy Fisher. The instrument was lowered through a 750m long borehole in the ice. We drove high resolution temperature sensors at the base of the probe into subglacial sediments, where they record the in situ temperature. We also collected a core of the subglacial sediments. Back in the lab, I measured their thermal conductivity. Since geothermal heat flux = thermal conductivity x temperature gradient, I could use this data to determine the geothermal heat flux.
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