Research ArticleENVIRONMENTAL SCIENCE

Geodetic measurements reveal similarities between post–Last Glacial Maximum and present-day mass loss from the Greenland ice sheet

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Science Advances  21 Sep 2016:
Vol. 2, no. 9, e1600931
DOI: 10.1126/sciadv.1600931
  • Fig. 1 Location map.

    Locations of the GNET GPS stations (red dots) and RSL observations (green dots). Black curves denote the major drainage basins numbered from 1 to 7; drainage 3 is separated into subbasins 3A and 3B (inset), the latter representing the near field of the KUAQ glacier. The yellow curve shows a reconstruction of the Iceland hot spot track (57, 58). Bathymetry is shown over the ocean and surface elevation over the land/ice (25).

  • Fig. 2 Uplift at KULU.

    (A) Daily GPS values of the vertical solutions at KULU, southeast Greenland. (B) Monthly mean values of the vertical solutions at KULU. The associated uncertainties are shown as vertical lines. The red curve denotes the estimated elastic vertical displacement based on load changes inferred from radar/laser altimetry observations. (C) Monthly mean values of vertical solutions after removing the annual, semiannual, and elastic vertical displacement, which represents the ongoing GIA vertical displacement from ice load changes following the LGM. Green line, ICE-5G GIA trend; blue, Green1 GIA trend; light blue, GPS inferred GIA trend; purple, HUY3 GIA trend; red, observed.

  • Fig. 3 Glacial isostatic adjustment.

    (A) Inferred GIA vertical displacement rates at GNET sites. Gray curves denote major drainage basins, and the numbers represent SLE estimates of each basin. (B) GIA vertical displacement rates from new model entitled “GNET-GIA.” (C) Uncertainties of GIA vertical displacement rates.

  • Fig. 4 GIA rates in basin 3B.

    Spatial pattern of GIA-induced uplift by the retreat of the KUAQ glaciers in the past century for different LT and AV; best fit to the measured GIA uplift is achieved for LT = 40 km and AV = 1 × 1019 Pa·s. The UMV and LMV are constant with 5 × 1020 and 2 × 1022 Pa·s, respectively (VM-GPS).

  • Table 1 Scale factors between inferred and predicted GIS rates for each basin and adopted viscosity profile.

    The LMV is 2 × 1022 Pa·s for all profiles. The asthenosphere thickness is set to 200 km.

    BasinScale factorViscosity profileNo. of RSL dataNo. of GPS sites
    LT (km)AV (1020 Pa·s)UMV (1020 Pa·s)
    11.04 ± 0.4560518010
    20.97 ± 0.36605256
    3A1.07 ± 0.336051607
    3B1.06 ± 0.20400.1502
    45.10 ± 0.41605010
    51.96 ± 0.45605133
    61.14 ± 0.566052819
    7A2.28 ± 0.24605562
    7B3.45 ± 0.3560515
    Total71654
  • Table 2 SLE mass change per basin.

    SLE estimates for each basin from Green1 and the new GPS-based deglaciation model.

    BasinGreen 1 SLE (m)Scaled Green1 SLE (m)SLE increase (%)
    10.840.87 ± 0.384
    20.650.63 ± 0.23−3
    3A0.280.30 ± 0.097
    3B0.100.11 ± 0.0210
    40.100.51 ± 0.04410
    50.110.21 ± 0.0591
    60.921.05 ± 0.5214
    7A0.110.25 ± 0.03127
    7B*0.090.70 ± 0.18678
    Total3.214.63 ± 0.7244

    *Load distribution modified (see text).

    Supplementary Materials

    • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/2/9/e1600931/DC1

      fig. S1. Locations of the permanent GPS stations in Greenland.

      fig. S2. Monthly mean values of vertical GPS solutions after removing the annual, semiannual, and elastic vertical displacement.

      fig. S3. Elevation change rate during 1997–2015.

      fig. S4. Time series of GrIS mass loss rate.

      fig. S5. Ice thickness change since the LGM as represented by the Green1 VM-GPS.

      fig. S6. GIA rates.

      fig. S7. Landsat image of southeast Greenland.

      table S1. Location of GPS sites, data time span, observed uplift rates, predicted elastic uplift rates, and observed GIA uplift rate.

      table S2. 1D viscosity profiles for Greenland.

      table S3. 1D viscosity profiles assigned to each region in Greenland.

      table S4. Uncertainty of the scaling parameter caused by the load and Earth model parameters.

      table S5. Ratio of inferred scaling factor for the 3D viscosity profiles versus the 1D viscosity profile (VM-GPS).

      table S6. SLE mass change per basin since LGM.

      table S7. SLE mass change per basin during 1900–1983.

    • Supplementary Materials

      This PDF file includes:

      • fig. S1. Locations of the permanent GPS stations in Greenland.
      • fig. S2. Monthly mean values of vertical GPS solutions after removing the annual, semiannual, and elastic vertical displacement.
      • fig. S3. Elevation change rate during 1997–2015.
      • fig. S4. Time series of GrIS mass loss rate.
      • fig. S5. Ice thickness change since the LGM as represented by the Green1 VM-GPS.
      • fig. S6. GIA rates.
      • fig. S7. Landsat image of southeast Greenland.
      • table S1. Location of GPS sites, data time span, observed uplift rates, predicted elastic uplift rates, and observed GIA uplift rate.
      • table S2. 1D viscosity profiles for Greenland.
      • table S3. 1D viscosity profiles assigned to each region in Greenland.
      • table S4. Uncertainty of the scaling parameter caused by the load and Earth model parameters.
      • table S5. Ratio of inferred scaling factor for the 3D viscosity profiles versus the 1D viscosity profile (VM-GPS).
      • table S6. SLE mass change per basin since LGM.
      • table S7. SLE mass change per basin during 1900–1983.

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