Geodetic and geomorphologic data assimilation into a coupled ice sheet / solid Earth model for separating present and past ice sheet behavior in Antarctica
Final Report Abstract
The Antarctic ice sheet (AntIS) is a key element in the climate system, interacting with the atmosphere, ocean and solid Earth in various ways, often insufficiently understood. DIEM aimed at improving our understanding the current and past evolution of the AntIS with simulations of a coupled ice sheet / solid Earth model. Important aspect of the project was isolating and including geodetic data of the ongoing glacial-isostatic adjustment (GIA) and geological evidence of the ice sheet geometry. The final aim was to predict, in a dynamically consistent way, the ongoing GIA, which is a major uncertainty in deriving mass balances of the ice sheet from GRACE satellite gravimetry. The project succeed in realizing coupled ice sheet/ solid Earth simulations of the glacial evolution of the AntIS from the past 40,000 years using both 1D and 3D Earth structures of the lithosphere and mantle. The resulting GIA prediction for a 1D Earth structure was submitted to the Ice Sheet Mass Balance Intercomparison Excercise (IMBIE2). In parallel, with support of the European Space Agency (ESA), the GIA signal in Antarctica was successfully estimated based on multiple space geodetic data (GRACE, GPS, altimetry) and compared to the coupled ice sheet / solid Earth model simulations (1D and 3D). The study involved the generation of viscoelastic response kernels, particularly accounting for the weak solid Earth structure associated with the West Antarctic rift system. Within the associated PhD project, the same coupled ice / solid Earth model was used to predict the future changes of the West Antarctic ice sheet. It could be shown that the comparatively fast and strong uplift detected for the Amundsen Sea Embayment (up to 20 mm/year induced by GIA), leads to a fall in relative sea-level, which may delay or even stabilize the decay of the West Antarctic Ice Sheet triggered for warming ocean temperatures. An unexpected side topic emerged when exceptionally high uplift rates were also recovered for southeast Greenland. In research funded within DIEM, it could be shown that the strong uplift results from the ice retreat of the past 100 years, in the presence of a low viscosity structure. During 2017, a new method for assimilating geological records of sea-level change together with GPS uplift rates into a forward GIA model was developed. Finally, contributions were made to formulating an adjoint method for GIA modelling and the gravimetric recovery of sediment layers in the region of the Pine Island glacier. Particularly, the results from Khan et al. (2016) received a lot of attention by media outlets (http://advances.sciencemag.org/content/2/9/e1600931/tab-articleinfo).
Publications
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(2015): Potential of the solid-Earth response for limiting long-term West Antarctic Ice Sheet retreat in a warming climate. Earth Plant. Sci. Lett., 432, 254-264
Konrad, H., Sasgen, I., Pollard, D. & Klemann, V.
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(2015): The forward sensitivity and adjoint-state methods of glacial isostatic adjustment. Geophys. J. Int., 200(1), 77-105
Martinec, Z., Sasgen, I., Velímský, J.
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(2016). Subglacial bathymetry and sediment distribution beneath Pine Island Glacier ice shelf modeled using aerogravity and in situ geophysical data: New results. Earth and Planetary Science Letters, 433, 63-75
Muto, A., Peters, L. E., Gohl, K., Sasgen, I., Alley, R. B., Anandakrishnan, S., & Riverman, K. L.
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(2016): Geodetic measurements reveal similarities between post–Last Glacial Maximum and present-day mass loss from the Greenland ice sheet, Sci. Adv. 21 Sep 2016: Vol. 2, no. 9, e1600931
Khan, S. A., Sasgen, I., Bevis, M., van Dam, T., Bamber, J. L.,Wahr, J., Willis, M., Kjær, K. H. Wouters, B., Helm, V., Csatho, B., Fleming, K., Bjørk, A. A., Aschwanden, A., Knudsen, P.
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(2016): Sensitivity of grounding-line dynamics to viscoelastic deformation of the solid-Earth in an idealized scenario. Polarforschung, 85, 2, 89-99
Konrad, H., Sasgen, I., Klemann, V., Thoma, M., Grosfeld, K., Martinec, Z.
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(2017), Joint inversion estimate of regional glacial isostatic adjustment in Antarctica considering a lateral varying Earth structure (ESA STSE Project REGINA), Geophys. J. Int.
Sasgen, I., Martín-Español, A., Horvath, A., Klemann, V., Petrie. E.J., Wouters, B., Horwath, M., Pail, R., Bamber, J.L., Clarke, P.J., Konrad, H. & Drinkwater, M. R.
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(2018), Altimetry, gravimetry, GPS and viscoelastic modelling data for the joint inversion for glacial isostatic adjustment in Antarctica (ESA STSE Project REGINA), Earth Syst. Sci. Data
Sasgen, I., Martín-Español, A., Horvath, A., Klemann, V., Petrie. E.J., Wouters, B., Horwath, M., Pail, R., Bamber, J.L., Clarke, P.J., Konrad, H., Wilson, T. & Drinkwater, M. R.
