The dynamics of the climate on a time scale of tens of thousands of years are affected by changes in the ice sheets and the sea level. Both act as a load that deforms the solid Earth. The deformations thus retroactively influence the climate-relevant surface processes in the atmosphere (changes in topography), in the ocean (changes in bathymetry) and in the ice sheets (changes in sea level at the ice edge and in the bedrock topography).
We focus on numerical modelling of ice sheet dynamics in response to climate variations; we model how the solid Earth responds to the ice mass changes and consider the gravitationally consistent feedback on the ice sheet that includes sea level variations influenced by GIA.
GIA mainly influences processes in the polar regions, as its influence on ice sheet dynamics is dominant. The following mechanisms are relevant:
Ice sheet-ocean:
Ice shelves are in direct contact with the water of the ocean at their bottom side. The temperature and circulation of the water in the ice shelf cavern, that is the volume below the ice shelf, determine the basal melt rates. They influence the thickness of the ice shelf and thus the position of the grounding line of the ice, which has a major influence on the dynamics of the neighbouring grounded ice sheet, its mass balance and thus the global mean sea level. On the other hand, the shape of the ice shelf cavern and the position of the grounding line, as well as the amount of freshwater introduced by melting, have a decisive influence on the circulation of the ocean beneath the ice shelf. Changes in sea level due to local or global processes thus change the size of the cavern, which has a retroactive effect on ice sheet dynamics and ocean circulation.
Ice sheet-atmosphere:
The albedo of the ice surface determines how much solar energy is reflected. Dust, algae growth and the characteristics of the firn are essentially characterised by atmospheric processes. Seasonal changes in temperature and water transport in the atmosphere also influence the mass balance and dynamics of the ice sheet through melting and precipitation rates. Vertical movements of the surrounding ocean surface and the ice sheet base caused by GIA influence the height of the ice relative to the atmosphere and thus the precipitation regime.
GIA primarily influences processes in the polar regions. However, its influence on the global distribution of sea level during a glacial cycle is also relevant, as it controls the drying of continental shelves and the temporally opening and closing of passages such as the Bering Strait or the Sunda Strait, and thus influences global ocean circulation.
Referenzen:
Willeit, M., Calov, R., Talento, S., Greve, R., Bernales, J., Klemann, V., Bagge, M., Ganopolski, A. (2024): Glacial inception through rapid ice area increase driven by albedo and vegetation feedbacks. - Climate of the Past, 20, 597-623. doi.org/10.5194/cp-20-597-2024
Albrecht, T., Bagge, M., Klemann, V. (2024): Feedback mechanisms controlling Antarctic glacial-cycle dynamics simulated with a coupled ice sheet–solid Earth model. - The Cryosphere, 18, 9, 4233-4255. doi.org/10.5194/tc-18-4233-2024
Höning, D., Willeit, M., Calov, R., Klemann, V., Bagge, M., Ganopolski, A. (2023): Multistability and transient response of the Greenland Ice Sheet to anthropogenic CO2 emissions. - Geophysical Research Letters, 50, 6, e2022GL101827. doi.org/10.1029/2022GL101827
Bernales, J., Rogozhina, I., Thomas, M. (2017): Melting and freezing under Antarctic ice shelves from a combination of ice-sheet modelling and observations. - Journal of Glaciology, 63, 240, 731-744. doi.org/10.1017/jog.2017.42
Timmermann, R., Goeller, S. (2017): Response to Filchner–Ronne Ice Shelf cavity warming in a coupled ocean–ice sheet model – Part 1: the ocean perspective. - Ocean Science, 13, 765-776. https://doi.org/10.5194/os-13-765-2017
Konrad, H., Sasgen, I., Klemann, V., Thoma, M., Grosfeld, K., Martinec, Z. (2016): Sensitivity of grounding-line dynamics to viscoelastic deformation of the solid-earth in an idealized scenario. -Polarforschung, 85, 2, p. 89-99. doi.org/10.2312/polfor.2016.005 | www.polarforschung.de/Inhalt/
Konrad, H., Thoma, M., Sasgen, I., Klemann, V., Grosfeld, K., Barbi, D., Martinec, Z. (2014): The deformational response of a viscoelastic solid earth model coupled to a thermomechanical ice sheet model. - Surveys in Geophysics, 35, 6, p. 1441-1458. doi.org/10.1007/s10712-013-9257-8
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