Preprints
https://doi.org/10.5194/tc-2021-95
https://doi.org/10.5194/tc-2021-95

  31 Mar 2021

31 Mar 2021

Review status: a revised version of this preprint was accepted for the journal TC and is expected to appear here in due course.

The Holocene dynamics of Ryder Glacier and ice tongue in north Greenland

Matt ORegan1,2, Thomas Cronin3, Brendan Reilly4, Aage Kristian Olsen Alstrup5, Laura Gemery3, Anna Golub3, Larry Mayer6, Mathieu Morlighem7, Matthias Moros8, Ole Lajord Munk5, Johan Nilsson2,9, Christof Pearce10, Henrieka Detlef10, Christian Stranne1,2, Flor Vermassen1,2, Gabriel West1,2, and Martin Jakobsson1,2 Matt ORegan et al.
  • 1Department of Geological Sciences, Stockholm University, 10691, Stockholm, Sweden
  • 2Bolin Centre for Climate Research, Stockholm University, 10691, Stockholm, Sweden
  • 3Florence Bascom Geoscience Center, U.S. Geological Survey, Reston, VA, 20192, USA
  • 4Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, 92037, USA
  • 5Department of Clinical Medicine Nuclear Medicine and PET, Aarhus University
  • 6Center for Coastal and Ocean Mapping, University of New Hampshire, Durham, NH, 03824, USA
  • 7Department of Earth System Science, University of California, Irvine, CA, 92697, USA
  • 8Leibniz Institute for Baltic Sea Research Warnemünde, D-18119, Rostock, Germany
  • 9Department of Meteorology, Stockholm University, 10691, Stockholm, Sweden
  • 10Department of Geoscience and Arctic Research Centre, Aarhus University, 8000, Aarhus, Denmark

Abstract. The northern sector of the Greenland ice sheet is considered to be particularly susceptible to ice mass loss arising from increased glacier discharge in the coming decades. However, the past extent and dynamics of outlet glaciers in this region, and hence their vulnerability to climate change, are poorly documented. In the summer of 2019, the Swedish icebreaker Oden entered the previously unchartered waters of Sherard Osborn Fjord, where Ryder Glacier drains approximately 2 % of Greenland's ice sheet into the Lincoln Sea. Here we reconstruct the Holocene dynamics of Ryder Glacier and its ice tongue by combining radiocarbon dating with sedimentary facies analyses along a 45 km transect of marine sediment cores collected between the modern ice tongue margin and the mouth of the fjord. The results illustrate that Ryder Glacier retreated from a grounded position at the fjord mouth during the Early Holocene (>10.7 ± 0.4 cal ka BP) and receded more than 120 km to the end of Sherard Osborn Fjord by the Middle Holocene (6.3 ± 0.3 cal ka BP), likely becoming completely land-based. A re-advance of Ryder Glacier occurred in the Late Holocene, becoming marine-based around 3.9 ± 0.4 cal ka BP. An ice tongue, similar in extent to its current position was established in the Late Holocene (between 3.6 ± 0.4 and 2.9 ± 0.4 cal ka BP) and extended to its maximum historical position near the fjord mouth around 0.9 ± 0.3 cal ka BP. Laminated, clast-poor sediments were deposited during the entire retreat and regrowth phases, suggesting the persistence of an ice tongue that only collapsed when the glacier retreated behind a prominent topographic high at the landward end of the fjord. Sherard Osborn Fjord narrows inland, is constrained by steep-sided cliffs, contains a number of bathymetric pinning points that also shield the modern ice tongue and grounding zone from warm Atlantic waters, and has a shallowing inland sub-ice topography. These features are conducive to glacier stability and can explain the persistence of Ryder’s ice tongue while the glacier remained marine-based. However, the physiography of the fjord did not halt the dramatic retreat of Ryder Glacier under the relatively mild changes in climate forcing during the Holocene. Presently, Ryder Glacier is grounded more than 40 km seaward of its inferred position during the Middle Holocene, highlighting the potential for substantial retreat in response to ongoing climate change.

Matt ORegan et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on tc-2021-95', Anonymous Referee #1, 30 Apr 2021
  • RC2: 'Comment on tc-2021-95', Anonymous Referee #2, 03 May 2021
    • AC2: 'Reply on RC2', Matt O'Regan, 24 Jun 2021
  • EC1: 'Comment on tc-2021-95', Chris R. Stokes, 27 May 2021
    • AC3: 'Reply on EC1', Matt O'Regan, 24 Jun 2021

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on tc-2021-95', Anonymous Referee #1, 30 Apr 2021
  • RC2: 'Comment on tc-2021-95', Anonymous Referee #2, 03 May 2021
    • AC2: 'Reply on RC2', Matt O'Regan, 24 Jun 2021
  • EC1: 'Comment on tc-2021-95', Chris R. Stokes, 27 May 2021
    • AC3: 'Reply on EC1', Matt O'Regan, 24 Jun 2021

Matt ORegan et al.

Matt ORegan et al.

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Short summary
Ryder Glacier is a marine terminating glacier in north Greenland discharging ice into the Lincoln Sea. Here we use marine sediment cores to reconstruct its retreat and advance behavior through the Holocene. We show that while Sherard Osborn Fjord has a physiography conducive to glacier and ice tongue stability, Ryder still retreated more than 40 km inland from its current position by the middle Holocene. This highlights the sensitivity of north Greenland's marine glaciers to climate change.