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The Cryosphere An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/tc-2018-51
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
02 May 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal The Cryosphere (TC).
Processes influencing near-surface heat transfer in Greenland's ablation zone
Benjamin H. Hills1,2, Joel T. Harper2, Toby W. Meierbachtol2, Jesse V. Johnson3, Neil F. Humphrey4, and Patrick J. Wright5,2 1Department of Earth and Space Sciences, University of Washington, Seattle, Washington, USA
2Department of Geosciences, University of Montana, Missoula, Montana, USA
3Department of Computer Science, University of Montana, Missoula, Montana, U SA
4Department of Geology and Geophysics, University of Wyoming, Laramie, Wyoming, USA
5Inversion Labs LLC, Wilson, Wyoming, USA
Abstract. To assess the influence of various mechanisms of heat transfer on the near-surface ice of Greenland's ablation zone, we incorporate highly resolved measurements of ice temperature into thermal modeling experiments. Seven separate temperature strings were installed at three different field sites, each with between 17 and 32 sensors and extending up to 20 m below the surface. In one string, temperatures were measured every 30 minutes, and the record is continuous for more than three years. We use these measured ice temperatures to constrain modeling analyses focused on four isolated processes to assess the relative importance of each to the near-surface ice temperature: 1) the moving boundary of an ablating surface, 2) thermal insulation by snow, 3) radiative energy input, and 4) temperature gradients below the seasonally active near-surface layer. In addition to these four processes, transient heating events were observed in two of the temperature strings. Despite no observations of meltwater pathways to the subsurface, these heating events are likely the refreezing of liquid water below 5–10 m of cold ice. Together with subsurface refreezing, the five heat transfer mechanisms presented here account for measured differences of up to 3 °C between the ice temperature at the depth where annual temperature variability is dissipated and the mean annual air temperature. Thus, in Greenland's ablation zone, the mean annual air temperature cannot be used to predict the near-surface ice temperature, as is commonly assumed.
Citation: Hills, B. H., Harper, J. T., Meierbachtol, T. W., Johnson, J. V., Humphrey, N. F., and Wright, P. J.: Processes influencing near-surface heat transfer in Greenland's ablation zone, The Cryosphere Discuss., https://doi.org/10.5194/tc-2018-51, in review, 2018.
Benjamin H. Hills et al.
Benjamin H. Hills et al.
Benjamin H. Hills et al.

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Short summary
At the surface, an ice sheet is closely connected to the climate. Assessing the way in which heat moves between the near-surface ice and the overlying air is important for understanding how the ice sheet is melting at the surface. We measured temperature within 20 meters of the surface of the Greenland ice sheet. These ice temperatures are warmer than the air, a peculiar result which implies that some more complicated processes are moving heat than purely conduction of the air temperature.
At the surface, an ice sheet is closely connected to the climate. Assessing the way in which...
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