Preprints
https://doi.org/10.5194/tc-2022-206
https://doi.org/10.5194/tc-2022-206
 
01 Nov 2022
01 Nov 2022
Status: this preprint is currently under review for the journal TC.

Direct measurement of warm Atlantic Intermediate Water close to the grounding line of Nioghalvfjerdsfjorden (79N) Glacier, North-east Greenland

Michael J. Bentley1, James A. Smith2, Stewart S. R. Jamieson1, Margaret Lindeman3, Brice R. Rea4, Angelika Humbert5,6, Timothy P. Lane7, Christopher M. Darvill8, Jeremy M. Lloyd1, Fiamma Straneo3, Veit Helm5, and David H. Roberts1 Michael J. Bentley et al.
  • 1Department of Geography, South Rd, Durham University, Durham, DH1 3LE, UK
  • 2British Antarctic Survey, High Cross, Madingley Rd, Cambridge, CB3 0ET, UK
  • 3Scripps Institution of Oceanography, University of California, San Diego, CA, USA
  • 4Geography and Environment, School of Geosciences, University of Aberdeen, Elphinstone Road, Aberdeen, AB24 3UF, UK
  • 5Alfred-Wegener-Institut, Helmholtz Zentrum für Polar- und Meeresforschung, Bremerhaven, Germany
  • 6Faculty of Geosciences, University of Bremen, Bremen, Germany
  • 7School of Biological and Environmental Sciences, Liverpool John Moores University, Liverpool, L3 3AF, UK
  • 8Department of Geography, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK

Abstract. The North-East Greenland Ice Stream has recently seen significant change to its floating margins, and has been identified as vulnerable to future climate warming. Inflow of warm Atlantic Intermediate Water (AIW) from the continental shelf has been observed in the vicinity of the Nioghalvfjerdsfjorden (79N) Glacier calving front, but AIW penetration deep into the ice shelf cavity has not been observed directly. Here, we report temperature and salinity measurements from profiles in an epishelf lake, which provide the first direct evidence of AIW proximal to the grounding line of 79N Glacier, over 50 km from the calving front. We also report evidence for partial un-grounding of the margin of 79N taking place at the western end of the epishelf lake. Comparison of our measurements to those close to the calving front shows that AIW transits the cavity to reach the grounding line within a few months. The observations provide support for modelling studies that infer AIW-driven basal melt proximal to the grounding line and demonstrate that offshore oceanographic changes can be rapidly transmitted throughout the sub-ice shelf cavity, with implications for near-future stability of the ice stream.

Michael J. Bentley et al.

Status: open (until 04 Jan 2023)

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Michael J. Bentley et al.

Michael J. Bentley et al.

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Short summary
The North-East Greenland Ice Stream is a major outlet of the Greenland ice sheet. Some of its outlet glaciers and ice shelves have been breaking up and retreating, with inflows of warm ocean water identified as the likely reason. Here we report direct measurements of warm ocean water in an unusual lake that is connected to the ocean beneath the ice shelf in front of the 79N Glacier. This glacier has not yet shown much retreat but the presence of warm water suggests may cause retreat.