Preprints
https://doi.org/10.5194/tc-2021-37
https://doi.org/10.5194/tc-2021-37

  02 Feb 2021

02 Feb 2021

Review status: a revised version of this preprint is currently under review for the journal TC.

Indication of high basal melting at EastGRIP drill site on the Northeast Greenland Ice Stream

Ole Zeising1,2 and Angelika Humbert1,2 Ole Zeising and Angelika Humbert
  • 1Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Bremerhaven, Germany
  • 2University of Bremen, Department of Geosciences, Germany

Abstract. The accelerated ice flow of ice streams that reach far into the interior of the ice sheet, is associate with lubrication of the ice sheet base by basal melt water. However, the amount of basal melting under the large ice streams – such as the Northeast Greenland Ice Stream (NEGIS) – are largely unknown. In-situ measurements of basal melt rates are important from various perspectives as they indicate the heat budget, the hydrological regime and the role of sliding in glacier motion. The few previous estimates of basal melt rates in the NEGIS region were 0.1 m a−1 and more, based on radiostratigraphy methods. These finding raised the question of the heat source, since even an increased geothermal heat flux could not deliver the necessary amount of heat. Here, we present basal melt rates at the recent deep drill site EastGRIP, located in the center of NEGIS. Within two subsequent years, we found basal melt rates of (0.16–0.22) ± 0.01 m a−1, that are based on analysis of repeated phase-sensitive radar measurements. In order to quantify the contribution of processes that cause a heat flux into the ice, we carried out an assessment of the energy sources and found the subglacial water system to play a key role in facilitating such high melt rates.

Ole Zeising and Angelika Humbert

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'express melt rate in mW/m2?', William Colgan, 08 Feb 2021
    • AC1: 'Reply on CC1', Ole Zeising, 11 Feb 2021
      • CC2: 'Reply on AC1', William Colgan, 11 Feb 2021
  • RC1: 'Comment on tc-2021-37', Basile de Fleurian, 12 Feb 2021
    • AC2: 'Reply on RC1', Ole Zeising, 07 Apr 2021
  • RC2: 'Comment on tc-2021-37', Anonymous Referee #2, 19 Mar 2021
    • AC3: 'Reply on RC2', Ole Zeising, 07 Apr 2021
  • RC3: 'Comment on tc-2021-37', Anonymous Referee #3, 19 Mar 2021
    • AC4: 'Reply on RC3', Ole Zeising, 07 Apr 2021

Ole Zeising and Angelika Humbert

Ole Zeising and Angelika Humbert

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Short summary
Greenland's largest ice stream – the Northeast Greenland Ice Stream (NEGIS) – extends far into the interior of the ice sheet. Basal meltwater acts as a lubricant for glaciers and sustains sliding. Hence, observations of basal melt rates are of high interest. We performed two time series of precise ground-based radar measurements in the upstream region of NEGIS and found high melt rates of 0.16–0.22 meters per year.