Elmer/Ice News

Elmer/Ice @EGU2019

The fifth Elmegu plainer/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

Joe Todd, Doug Benn, Tom Cowton, Jan Åstrom, and Thomas Zwinger, 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

Thomas Zwinger, Juha Hartikainen, and Denis Cohen, A high-resolution coupled permafrost - ice sheet model - Mon, 08 Apr, 14:15–14:30 Room N2

Daniel Farinotti, Matthias Huss, Johannes J. Fürst, Johannes Landmann, Horst Machguth, Fabien Maussion, and Ankur Pandit, A consensus estimate for the ice thickness distribution of all glaciers on Earth - Mon, 08 Apr, 17:15–17:30 Room 1.85

Tom Cowton, Joe Todd, and Doug Benn, 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

Johannes J. Fürst, Mapping glacier ice thickness in Patagonia - Tue, 09 Apr, 16:15–18:00 Hall X4

Samuel Cook, Poul Christoffersen, Joe Todd, Donald Slater, and Nolwenn Chauché, 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

Doug Benn, Jan Åström, Thomas Zwinger, Joe Todd, and Anna Crawford, Marine Ice-cliff instability: How Does it Work, and What Controls Ice Retreat Rates? - Wed, 10 Apr, 15:00–15:15 Room N2
Eef van Dongen, Andrea Walter, Guillaume Jouvet, Martin Funk, Joe Todd, Jan Åström, and Thomas Zwinger, Monitoring and modeling a recurrent major calving event at Bowdoin Glacier, Greenland - Wed, 10 Apr, 11:15–11:30 Room N2

A consensus estimate for the ice thickness distribution of all glaciers on Earth

farinotti2019Elmer/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

Sensitivity of centennial mass loss projections of the Amundsen basin to the friction law

julien2019Reliable projections of ice sheets’ future contributions to sea-level rise require models that are able to accurately simulate grounding-line dynamics, starting from initial states consistent with observations. In this new article, we use Elmer/Ice to simulate the centennial evolution of the Amundsen Sea Embayment (the most active drainage basin of the antarctic ice sheet) in response to a prescribed perturbation in order to assess the sensitivity of mass loss projections to the chosen friction law, depending on the initialisation strategy. To this end, we take advantage of inverse methods implemented in Elmer/Ice to construct three different model states by inferring both the initial basal shear stress and viscosity fields with various relative weights. Then, starting from each of these model states, prognostic simulations are carried out using a Weertman, a Schoof and a Budd friction law, with different parameter values. These experiments demonstrate that although the sensitivity of projections to the chosen friction law tends to decrease when more weight is put on viscosity during initialisation, it remains significant for the most physically acceptable of the constructed model states. In addition, it turns out that independently of the considered model state, the Weertman law systematically predicts the lowest mass losses. Finally, because of its particular dependence on effective pressure, the Budd friction law induces significantly different grounding-line retreat patterns than the other laws and predicts significantly higher mass losses. These conclusions urge the scientific community to undertake major efforts in order to get a better understanding of processes at the root of basal motion, with the aim of developing reliable friction laws that could be used in models to produce accurate estimates of future contribution of ice sheets to sea level rise.

Read more: Brondex J., F. Gillet-Chaulet and O. Gagliardini, 2019. Sensitivity of centennial mass loss projections of the Amundsen basin to the friction law, The Cryosphere, 13, 177-195, https://doi.org/10.5194/tc-13-177-2019

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