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
Elmer/Ice was one of the five models participating in this exercice to improve the estimate of the ice thickness distribution of all glaciers on Earth.
Knowledge of the ice thickness distribution of the world’s glaciers is a fundamental prerequisite for a range of studies. Projections of future glacier change, estimates of the available freshwater resources or assessments of potential sea-level rise all need glacier ice thickness to be accurately constrained. Previous estimates of global glacier volumes are mostly based on scaling relations between glacier area and volume, and only one study provides global-scale information on the ice thickness distribution of individual glaciers. Here we use an ensemble of up to five models to provide a consensus estimate for the ice thickness distribution of all the about 215,000 glaciers outside the Greenland and Antarctic ice sheets. The models use prin- ciples of ice flow dynamics to invert for ice thickness from surface characteristics. We find a total volume of 158 ± 41 × 103 km3, which is equivalent to 0.32 ± 0.08 m of sea-level change when the fraction of ice located below present-day sea level (roughly 15%) is subtracted. Our results indicate that High Mountain Asia hosts about 27% less glacier ice than previously suggested, and imply that the timing by which the region is expected to lose half of its present-day glacier area has to be moved forward by about one decade.
Read more: Farinotti D., H. Matthias, J. Fürst, J. Landmann, H. Machguth, F. Maussion and A. Pandit, 2019. A consensus estimate for the ice thickness distribution of all glaciers on Earth, Nature Geoscience, doi:10.1038/s41561-019-0300-3