Preprints
https://doi.org/10.5194/tc-2021-262
https://doi.org/10.5194/tc-2021-262

  29 Sep 2021

29 Sep 2021

Review status: this preprint is currently under review for the journal TC.

Layered seawater intrusion and melt under grounded ice

Alexander A. Robel1, Earle Wilson2, and Helene Seroussi3,4 Alexander A. Robel et al.
  • 1School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA
  • 2Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
  • 3Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
  • 4Thayer School of Engineering, Dartmouth College, Hanover, NH, USA

Abstract. Increasing melt of ice sheets at their floating or vertical interface with the ocean is a major driver of marine ice sheet retreat and sea level rise. However, the extent to which warm, salty seawater may drive melting under the grounded portions of ice sheets is still not well understood. Previous work has explored the possibility that dense seawater intrudes beneath relatively light subglacial freshwater discharge, similar to the salt wedge observed in many estuarine systems. In this study, we develop a generalized theory of layered seawater intrusion under grounded ice, including where subglacial hydrology occurs as a macroporous water sheet over impermeable beds or as microporous Darcy flow through permeable till. Using predictions from this theory, we show that seawater intrusion over hard beds may feasibly occur up to tens of kilometers upstream of a glacier terminus or grounding line. On the other hand, seawater is unlikely to intrude more than tens of meters through subglacial till. High-resolution simulations using the Ice-Sheet and Sea-Level System Model (ISSM) show that even just a few hundred meters of basal melt caused by seawater intrusion upstream of marine ice sheet grounding lines can cause projections of marine ice sheet volume loss to be 10–50 % higher or 100 % higher for kilometers of intrusion-induced basal melt. These results suggest that further observational, experimental and numerical investigations are needed to determine whether the conditions under which extensive seawater intrusion occurs and whether it will indeed drive rapid marine ice sheet retreat and sea level rise in the future.

Alexander A. Robel et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on tc-2021-262', Anonymous Referee #1, 07 Oct 2021
    • AC1: 'Reply on RC1', Alexander Robel, 23 Nov 2021
  • RC2: 'Comment on tc-2021-262', Anonymous Referee #2, 27 Oct 2021
    • RC3: 'Reply on RC2 (addendum to reviewer comment 2)', Anonymous Referee #2, 03 Nov 2021
    • AC2: 'Reply on RC2', Alexander Robel, 23 Nov 2021

Alexander A. Robel et al.

Alexander A. Robel et al.

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Short summary
Seawater is denser than meltwater under glaciers and may intrude in a thin layer underneath glaciers which are in contact with the ocean. Mathematical theory predicts that this intrusion may extend over many tens of kilometers under realistic conditions. Computer models demonstrate that ice melt from this intrusion under marine ice sheets, like Antarctica, can cause a doubling of ice loss and sea level rise in response to potential future ocean warming.