Elmer/Ice News

A closer look on ISMIP6-Antarctica results

In this latest article on ISMIP6-Antarctica intercomparison (including contribution from Elmer/Ice),  a closer look is taken on the results for high carbon emission tc 17 5197 2023 avatar webscenarios. The work focuses on key glaciers around the Antarctic Ice Sheet in order to quantify their projected dynamic mass loss through increased ice discharge into the ocean in response to changing oceanic conditions. Particular attention is given to glaciers contributing the most to sea level rise, as well as their vulnerability to changes in oceanic conditions.  These key glaciers - alongside the whole ice-sheet - in the further are investigated for the different sources of uncertainty and their relative role in projections. The findings are that in addition to the "usual suspects" in W-Antarctic ice-sheet (that be Thwaites and Pine Island) also outlet systems in E-Antarctica (Moscow University and Totten) show high sensitivity to increased oceanic ice-melt. Further, the uncertainties of the choice of climate models and the parametrization of the ocean melt have been investigated. Yet, overall, the highest uncertainty in dynamic ice-loss seems to be coming from the choice of the ice-sheet model. 

Read more:

Seroussi, H., Verjans, V., Nowicki, S., Payne, A. J., Goelzer, H., Lipscomb, W. H., Abe-Ouchi, A., Agosta, C., Albrecht, T., Asay-Davis, X., Barthel, A., Calov, R., Cullather, R., Dumas, C., Galton-Fenzi, B. K., Gladstone, R., Golledge, N. R., Gregory, J. M., Greve, R., Hattermann, T., Hoffman, M. J., Humbert, A., Huybrechts, P., Jourdain, N. C., Kleiner, T., Larour, E., Leguy, G. R., Lowry, D. P., Little, C. M., Morlighem, M., Pattyn, F., Pelle, T., Price, S. F., Quiquet, A., Reese, R., Schlegel, N.-J., Shepherd, A., Simon, E., Smith, R. S., Straneo, F., Sun, S., Trusel, L. D., Van Breedam, J., Van Katwyk, P., van de Wal, R. S. W., Winkelmann, R., Zhao, C., Zhang, T., and Zwinger, T., 2023. Insights into the vulnerability of Antarctic glaciers from the ISMIP6 ice sheet model ensemble and associated uncertaintyThe Cryosphere 17. doi:10.5194/tc-17-5197-2023

ISMIP6, Elmer/Ice

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GeoMIP scenarios applied to the Greenland ice sheet

Stratospheric Aerosol Injection (SAI) is a highly debated topic. The more it is important to look into the science (objectively,jgrf21835 fig 0006 m small without an agenda).  In order to contribute to this process, two ice dynamic models (SICOPOLIS and Elmer/Ice) driven by changes in surface mass balance (SMB) from four climate models to estimate the SLR contribution under the Intergovernmental Panel on Climate Change (IPCC) Representative Concentration Pathway (RCP) 4.5, and 8.5, and Geoengineering Model Intercomparison Project G4 scenarios were deployed for the Greenland ice sheet. The G4 scenario adds 5 Tg/yr sulfate aerosols to the equatorial lower stratosphere (equivalent of 1/4 the 1991 Mt Pinatubo SO2 eruption) to the IPCC RCP4.5 scenario, which itself approximates the greenhouse gas emission commitments agreed in Paris in 2015. In the applied setups for the 2020–2090 period, the two ice sheet models show a reduction of mass loss between 31%–38% for the G4 compared to RCP4.5 scenario, which itself compared to RCP8.5 shows a lowering of 36%–48%. Both, the G4 and the 4.5 scenario indicate a lowering of the ice-flux across the grounding line into the ocean, as glaciers retreat from the coast and become land-terminated, with an exception of low-lying catchments (e.g., Jakobshavn, 79N, Zachariae Isstrøm, and Petermann glaciers)  that show an increased flux under RCP 4.5 compared to G4. Despite a dominating  variation of calving losses compared to differences in SMB between SICOPOLIS and Elmer/Ice, ice discharge losses are significant, ranging from 15% up to 42%, depending on the scenario. Picture (taken from the publication) to the right shows differences of the ensembles in flux and ice thickness between G4 and RCP4.5 runs.

Read more:

Moore, J. C., R. Greve, C. Yue, T.  Zwinger, F. Gillet-Chaulet, and L. Zhao, 2023. Reduced Ice Loss From Greenland Under Stratospheric Aerosol InjectionJournal of Geophysical Research: Earth Surface, 128. doi:10.1029/2023JF007112

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Higher-order fabric structure in a coupled, anisotropic ice-flow model

lilien2023Ice-crystal fabric can induce mechanical anisotropy that significantly affects flow, but ice-flow models generally do not include fabric development or its effect upon flow. Here, we incorporate a new spectral expansion of fabric, and more complete description of its evolution, into the ice-flow model Elmer/Ice. This approach allows us to model the effect of both lattice rotation and migration recrystallization on large-scale ice flow. The fabric evolution is coupled to flow using an unapproximated non-linear orthotropic rheology that better describes deformation when the stress and fabric states are misaligned. These improvements are most relevant for simulating dynamically interesting areas, where recrystallization can be important, tuning data are scarce and rapid flow can lead to misalignment between stress and fabric. We validate the model by comparing simulated fabric to ice-core and phase-sensitive radar measurements on a transect across Dome C, East Antarctica. With appropriately tuned rates for recrystallization, the model is able to reproduce observations of fabric. However, these tuned rates differ from those previously derived from laboratory experiments, suggesting a need to better understand how recrystallization acts differently in the laboratory compared to natural settings.

Read more: Lilien, D., N. Rathmann, C. Hvidberg, A. Grinsted, M. Ershadi, R. Drews and D. Dahl-Jensen, 2023. Simulating higher-order fabric structure in a coupled, anisotropic ice-flow model: Application to Dome CJournal of Glaciology, 1-20. doi:10.1017/jog.2023.78

 

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