Numerics

Our group has co-founded the Ice Sheet System Model in partnership between UC Irvine and the NASA Jet Propulsion Laboratory. ISSM is a large scale, high-resolution, massively parallelized finite element model dedicated to ice sheet modeling and is our primary tool. Our work on improving numerical methods include:

Data assimilation

Inverse methods, that combine ice sheet modeling and surface observations, provide the tools to tackle these questions. We have used inverse methods to investigate the patterns of basal friction under grounded ice using surface velocities derived from Satellite interferometry (Morlighem et al. 2011). More recently, we have applied these techniques at the scale of Antarctica (Morlighem et al. 2013) and we discovered that basal sliding is widespread beneath the Antarctic Ice Sheet. This suggests that coastal perturbations may be transmitted further inland than expected. More recently we have been working on automatic differentiation (with ADOLC, TAPENADE and CoDiPack) to invert for any model input parameter.

Mesh adaptation

A high mesh resolution is critical in some key regions such as grounding lines, ice fronts, or shear margins. In order to maintain a good model accuracy while minimizing the computational cost of large scale models, we have been developing:

• Static anisotropic mesh refinement (through the development of BAMG)
• Adaptive mesh refinement (AMR)

Implementation of subelement physical processes

It has been shown that tracking the grounding line at the subelement level relaxes the requirements on mesh resolution. We have been investigating the impact of subelement parameterizations on basal friction and ocean-induced melt in the vicinity of the grounding line in order to establish the most efficient strategies for accurate modeling of grounding line dynamics.

Linear solvers

The linear solver is the main bottleneck in large scale simulations. We are working on testing new generation solvers to improve the performance of the model.

Selected publications

• T.D. dos Santos, M. Morlighem, H. Seroussi, P.R.B. Devloo and J.C. Simões, Implementation and performance of adaptive mesh refinement in the Ice Sheet System Model (ISSM v4.14), Geoscientific Model Development 12 (2019) 215-32 [link]
• H. Seroussi and M. Morlighem, Representation of basal melting at the grounding line in ice flow models, The Cryosphere 12 (2018) 3085-96 [link]
• J.K. Cuzzone, M. Morlighem, E. Larour, N. Schlegel and H. Seroussi, Implementation of higher-order vertical finite elements in ISSM v4.13 for improved ice sheet flow modeling over paleoclimate timescales, Geoscientific Model Development 11 (2018) 1683-94 [link]
• L. Hascoët and M. Morlighem, Source-to-source adjoint Algorithmic Differentiation of an ice sheet model written in C, Optimization Methods and Software 33 (2017) 829-43 [link]
• F. Habbal, E. Larour, M. Morlighem, H. Seroussi, C.P. Borstad and E. Rignot, Optimal numerical solvers for transient simulations of ice flow using the Ice Sheet System Model (ISSM versions 4.2.5 and 4.11), Geoscientific Model Development 10 (2017) 155-68 [link]
• E. Larour, J. Utke, A. Bovin, M. Morlighem and G. Perez, An approach to computing discrete adjoints for MPI-parallelized models applied to Ice Sheet System Model 4.11, Geoscientific Model Development 9 (2016) 3907-18 [link]
• E. Larour, J. Utke, B. Csatho, A. Schenk, H. Seroussi, M. Morlighem, E. Rignot, N. Schlegel and A. Khazendar, Inferred basal friction and surface mass balance of the Northeast Greenland Ice Stream using data assimilation of ICESat (Ice Cloud and land Elevation Satellite) surface altimetry and ISSM (Ice Sheet System Model), The Cryosphere 8 (2014) 2335-51 [link]
• H. Seroussi, M. Morlighem, E. Larour, E. Rignot and A. Khazendar, Hydrostatic grounding line parameterization in ice sheet models, The Cryosphere 8 (2014) 2075-87 [link]
• M. Morlighem, H. Seroussi, E. Larour and E. Rignot, Inversion of basal friction in Antarctica using exact and incomplete adjoints of a higher-order model, Journal of Geophysical Research: Earth Surface 118 (2013) 1746-53 [link]
• E. Larour, H. Seroussi, M. Morlighem and E. Rignot, Continental scale, high order, high spatial resolution, ice sheet modeling using the Ice Sheet System Model (ISSM), Journal of Geophysical Research: Earth Surface 117 (2012) n/a-n/a [link]
• M. Morlighem, E. Rignot, H. Seroussi, E. Larour, H. Ben Dhia and D. Aubry, Spatial patterns of basal drag inferred using control methods from a full-Stokes and simpler models for Pine Island Glacier, West Antarctica, Geophysical Research Letters 37 (2010) n/a-n/a [link]