Total isostatic response to the complete unloading of the Greenland and Antarctic Ice Sheets

Abstract

The land surface beneath the Greenland and Antarctic Ice Sheets is isostatically suppressed by the mass of the overlying ice. Accurate computation of the land elevation in the absence of ice is important when considering, for example, regional geodynamics, geomorphology, and ice sheet behaviour. Here, we use contemporary compilations of ice thickness and lithospheric effective elastic thickness to calculate the fully re-equilibrated isostatic response of the solid Earth to the complete removal of the Greenland and Antarctic Ice Sheets. We use an elastic plate flexure model to compute the isostatic response to the unloading of the modern ice sheet loads, and a self-gravitating viscoelastic Earth model to make an adjustment for the remaining isostatic disequilibrium driven by ice mass loss since the Last Glacial Maximum. Feedbacks arising from water loading in areas situated below sea level after ice sheet removal are also taken into account. In addition, we quantify the uncertainties in the total isostatic response associated with a range of elastic and viscoelastic Earth properties. We find that the maximum change in bed elevation following full re-equilibration occurs over the centre of the landmasses and is +783 m in Greenland and +936 m in Antarctica. By contrast, areas around the ice margins experience up to 123 m of lowering due to a combination of sea level rise, peripheral bulge collapse, and water loading. The computed isostatic response fields are openly accessible and have a number of applications for studying regional geodynamics, landscape evolution, cryosphere dynamics, and relative sea level change.

Geologic Provinces Beneath the Greenland Ice Sheet Constrained by Geophysical Data Synthesis

“…For panels C and D, Operation IceBridge airborne gravity and magnetic data are overlain (Cochran & Bell, 2016; Cochran et al., 2014; K. Tinto, 2020). (e) Isostatically rebounded BedMachine v5 topography assuming ice‐free conditions (Morlighem et al., 2017, 2022; Paxman et al., 2022a, 2022b). (f) GrIMP hillshade with surface‐exposed provinces and major faults (Harrison et al., 2011; Watt, 2019).…”

“…Tinto, 2020). (e) Isostatically rebounded BedMachine v5 topography assuming ice-free conditions (Morlighem et al, 2017(Morlighem et al, , 2022Paxman et al, 2022aPaxman et al, , 2022b. (f) GrIMP hillshade with surface-exposed provinces and major faults (Harrison et al, 2011;Watt, 2019).…”

Subglacial topography and landscape evolution from radio-echo sounding data in the Evans-Rutford Region, southern Antarctic Peninsula.

“…In order to provide insight into the age and genesis of the landscape, a flexural isostatic correction rebound grid (Paxman et al, 2021) was applied to the DEM in order to produce a model of rebounded elevations as they might have looked if we were to assume that they were formed before the region was covered by an ice sheet. The model uses contemporary ice thickness and lithospheric effective elastic thickness to calculate the fully re-equilibrated flexural isostatic response of the bedrock topography to the complete removal of the modern ice sheet load (Paxman et al, 2022). This resulting rebounded DEM was then subject to hypsometric analysis to enable comparison against the nonrebounded DEM.…”

“…A flexural isostatic rebounding model (Paxman et al, 2022) was applied to the DEM, in order to determine the pre-glaciation landscape by adjusting elevations to account for ice loading. This allows for an understanding of the elevations at which the plateaux surfaces may have sat if they were to have existed prior to the onset of glaciation in Antarctica.…”

“…The extent of this effect would also be dependent upon the relative rigidity of the lithosphere: within this region of West Antarctica, there is a low effective elastic thickness value, resulting in shorter wavelength variability in isostatic uplift (Paxman et al, 2022). Flexural uplift may also be contributed to by resultant unloading of the footwall by the hanging wall in troughs that are subject to fault bounding, as demonstrated in the Shackleton Range (Paxman et al, 2017).…”