Iceberg calving accounts for between 30 % and 60% of net mass loss from the Greenland Ice Sheet, which has intensified and is now the single largest contributor to global sea level rise in the cryosphere. Changes to calving rates and the dynamics of calving glaciers represent a significant uncertainty in projections of future sea level rise. A growing body of observational evidence suggests that calving glaciers respond rapidly to regional environmental change, but predictive capacity is limited by the lack of suitable models capable of simulating calving mechanisms realistically. Here, we use a 3-D full-Stokes calving model to investigate the environmental sensitivity of Store Glacier, a large outlet glacier in West Greenland. We focus on two environmental processes: undercutting by submarine melting and buttressing by ice mélange, and our results indicate that Store Glacier is likely to be able to withstand moderate warming perturbations in which the former is increased by 50 % and the latter reduced by 50%. However, severe perturbation with a doubling of submarine melt rates or a complete loss of ice mélange destabilises the calving front in our model runs. Furthermore, our analysis reveals that stress and fracture patterns at Store’s terminus are complex and varied, primarily due to the influence of basal topography. Calving style and environmental sensitivity vary greatly, with propagation of surface crevasses significantly influencing iceberg production in the northern side, whereas basal crevasses dominate in the south. Any future retreat is likely to be initiated in the southern side by a combination of increased submarine melt rates in summer and reduced mélange strength in winter. The lateral variability, as well as the importance of rotational and bending forces at the terminus, underlines the importance of using the 3-D full-Stokes stress solution when modelling Greenland’s calving glaciers.
Read more: Todd, J., Christoffersen, P., Zwinger, T., Råback, P., and Benn, D. I, 2019. Sensitivity of a calving glacier to ice–ocean interactions under climate change: new insights from a 3-D full-Stokes model. The Cryosphere, 13, 1681-1694, https://doi.org/10.5194/tc-13-1681-2019
Ice sheet numerical modeling is an important tool to estimate the dynamic contribution of the Antarctic ice sheet to sea level rise over the coming centuries. The influence of initial conditions on ice sheet model simulations, however, is still unclear. To better understand this influence, an initial state intercomparison exercise (initMIP) has been developed to compare, evaluate, and improve initialization procedures and estimate their impact on century-scale simulations. initMIP is the first set of experiments of the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6), which is the primary Coupled Model Intercomparison Project Phase 6 (CMIP6) activity focusing on the Greenland and Antarctic ice sheets. Following initMIP-Greenland, initMIP-Antarctica has been designed to explore uncertainties associated with model initialization and spin-up and to evaluate the impact of changes in external forcings. Starting from the state of the Antarctic ice sheet at the end of the initialization procedure, three forward experiments are each run for 100 years: a control run, a run with a surface mass balance anomaly, and a run with a basal melting anomaly beneath floating ice. This study presents the results of initMIP-Antarctica from 25 simulations performed by 16 international modeling groups. The submitted results use different initial conditions and initialization methods, as well as ice flow model parameters and reference external forcings. We find a good agreement among model responses to the surface mass balance anomaly but large variations in responses to the basal melting anomaly. These variations can be attributed to differences in the extent of ice shelves and their upstream tributaries, the numerical treatment of grounding line, and the initial ocean conditions applied, suggesting that ongoing efforts to better represent ice shelves in continental-scale models should continue.
The fifth Elmer/Ice users splinter meeting will take place Tuesday 9 April at 12h45, Room 2.61! This is an informal meeting, come with your sandwich and some slides you would like to share with the other Elmer/Ice users.
Here is the list of the presentations that will be given during EGU2019 and that include Elmer/Ice modeling:
Olivier Gagliardini, Accounting for transient effects in water pressure in friction law - Mon, 08 Apr, 09:30–09:45 Room L6
, New insights into glacier calving and environmental sensitivity from a combined continuum & discrete 3D modelling approach - Mon, 08 Apr, 11:45–12:00 Room L6
, A high-resolution coupled permafrost - ice sheet model - Mon, 08 Apr, 14:15–14:30 Room N2
, Sensitivity of calving rates to plume melting at an idealised tidewater glacier - Tue, 09 Apr, 14:00–15:45 Hall X4
Fabien Gillet-Chaulet, Transient calibration of a marine ice sheet model using an ensemble Kalman filter - Tue, 09 Apr, 16:15–18:00 Hall X4
Mapping glacier ice thickness in Patagonia - Tue, 09 Apr, 16:15–18:00 Hall X4
, Integrated investigation of subglacial hydrology and convective plume melting using a 3D full-Stokes model of Store Glacier, West Greenland - Wed, 10 Apr, 11:45–12:00 Room N2