Inland thinning on the Greenland ice sheet controlled by outlet glacier geometry

Journal name:
Nature Geoscience
Volume:
10,
Pages:
366–369
Year published:
DOI:
doi:10.1038/ngeo2934
Received
Accepted
Published online

Abstract

Greenlands contribution to future sea-level rise remains uncertain and a wide range of upper and lower bounds has been proposed. These predictions depend strongly on how mass loss—which is focused at the termini of marine-terminating outlet glaciers—can penetrate inland to the ice-sheet interior. Previous studies have shown that, at regional scales, Greenland ice sheet mass loss is correlated with atmospheric and oceanic warming. However, mass loss within individual outlet glacier catchments exhibits unexplained heterogeneity, hindering our ability to project ice-sheet response to future environmental forcing. Using digital elevation model differencing, we spatially resolve the dynamic portion of surface elevation change from 1985 to present within 16 outlet glacier catchments in West Greenland, where significant heterogeneity in ice loss exists. We show that the up-glacier extent of thinning and, thus, mass loss, is limited by glacier geometry. We find that 94% of the total dynamic loss occurs between the terminus and the location where the down-glacier advective speed of a kinematic wave of thinning is at least three times larger than its diffusive speed. This empirical threshold enables the identification of glaciers that are not currently thinning but are most susceptible to future thinning in the coming decades.

At a glance

Figures

  1. Dynamic surface elevation change and mass loss.
    Figure 1: Dynamic surface elevation change and mass loss.

    Surface elevation change from DEM differencing from 1985–present with surface mass balance (SMB) anomaly removed. Labels pertain to glacier names listed in Supplementary Table 2. Differences plotted on top of GIMP surface classification mask25 with ice in white, ocean in light grey, and bedrock in dark grey. Circle areas are proportional to dynamic mass gain (blue) or loss (red).

  2. Centreline profile of Kangilernata Sermia (KAN).
    Figure 2: Centreline profile of Kangilernata Sermia (KAN).

    a, Elevations relative to the WGS-84 ellipsoid for 1985 (blue) and present-day (red) glacier surfaces and mass-conserving bed20 (black) along the glacier centreline. b, Dynamic surface elevation change (black) with uncertainty from standard error propagation (grey, Methods). Moving average within window of 10 local ice thicknesses coloured by percentage of unit volume loss. c, Péclet number (Pe) calculated from the 1985 surface (black) with Pe running maximum (red). Shading reflects uncertainty (on the order of ±0.25 in this example) from standard error propagation (Methods).

  3. Peclet number running maxima and percentage unit volume loss.
    Figure 3: Péclet number running maxima and percentage unit volume loss.

    a, Percentage unit volume loss plotted against the running maximum Pe for 11 dynamically thinning West Greenland outlet glaciers. Median percentage unit volume loss within bins of width 1 Pe are calculated for each glacier and black dots are medians of the glacier median values with error bars representing the 25th and 75th percentiles of percentage unit volume loss. b, Pe for 16 West Greenland outlet glaciers along their centrelines. Locations where the Pe first exceeds 3 are marked for each glacier.

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Author information

  1. Present address: Department of Geological Sciences, University of Idaho, Moscow, Idaho 83844, USA.

    • Timothy C. Bartholomaus

Affiliations

  1. Institute for Geophysics, University of Texas at Austin, Austin, Texas 78758, USA

    • Denis Felikson,
    • Timothy C. Bartholomaus &
    • Ginny A. Catania
  2. Department of Aerospace Engineering and Engineering Mechanics, University of Texas at Austin, Austin, Texas 78705, USA

    • Denis Felikson
  3. Department of Geological Sciences, University of Texas at Austin, Austin, Texas 78705, USA

    • Ginny A. Catania
  4. Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, IS-101 Reykjavik, Iceland

    • Niels J. Korsgaard
  5. Centre for GeoGenetics, Natural History Museum, University of Copenhagen, Copenhagen 1350, Denmark

    • Kurt H. Kjær
  6. Department of Earth System Science, University of California, Irvine, California 92697, USA

    • Mathieu Morlighem
  7. Institute for Marine and Atmospheric Research Utrecht, Utrecht University, 3584 CC Utrecht, The Netherlands

    • Brice Noël &
    • Michiel van den Broeke
  8. Department of Geology, University of Kansas, Lawrence, Kansas 66045, USA

    • Leigh A. Stearns
  9. College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA

    • Emily L. Shroyer &
    • Jonathan D. Nash
  10. Department of Geological Sciences, University of Oregon, Eugene, Oregon 97403, USA

    • David A. Sutherland

Contributions

D.F., T.C.B. and G.A.C. designed the study. D.F. created the WorldView DEMs, calculated catchment mass changes, and performed the kinematic wave analysis. D.F., T.C.B. and G.A.C. interpreted the results. N.J.K. and K.H.K. created the 1985 DEM. M.M. processed the mass-conserving bed for the study region. B.N. and M.v.d.B. provided downscaled SMB data. All authors discussed the results and commented on the manuscript.

Competing financial interests

The authors declare no competing financial interests.

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