The Finite Element Louvain-la-Neuve sea-Ice Model (FELIM)
We are currently developing a finite element sea-ice model. This uncoupled model has representations of both dynamic and thermodynamic sea-ice processes and includes viscous-plastic rheology along with a complete parametrization of the atmospheric fluxes. The computation of the vertical growth/melt rate of the ice is based on Semtner’s (1976) zero-layer model. In the following results, numerical simulations are performed over 1979-2005, forced by daily NCEP/NCAR reanalysis data.
Unstructured meshes, with their natural ability to fit boundaries and increase locally the mesh resolution, propose an alternative framework to capture the complex oceanic areas formed by coasts and islands. In particular, we investigate the influence of resolving the narrow straits of the Canadian Arctic Archipelago (CAA) on the sea-ice features in the Arctic (Lietaer et al., 2008).
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| Finite element mesh of the Arctic with a close-up of the Canadian Arctic Archipelago. The domain extends north of the parallel 50° North. The mesh contains 17,053 triangles and 10,505 nodes and its resolution varies from 10 to 400 km. |
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| Mean climatological (1979-2005) ice thickness animation of Arctic sea-ice. Days of the year are indicated. |
In order to evaluate the importance of the CAA for the mass balance of Arctic sea-ice, we evaluate the sea-ice volume in the CAA by summing the contributions of all the elements situated inside a restricted area supposed to englobe the whole CAA (see figure below). According to our model, the mean CAA ice mass represents a rough 10% of the total simulated sea-ice volume, which is far from being negligible.
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| Importance of the Canadian Arctic Archipelago for the mass balance of the Arctic. Left: close-up view of the mesh in the CAA. Right: seasonal cycles of the Arctic sea-ice volume with (solid) and without (dashed) the contribution of the CAA. All the elements included in the blue triangle in the left figure are considered being part of the CAA. | |
Other recent numerical efforts include the development of a Lagrangian, adaptive sea-ice model allowing the computational grid to move with the ice drift. In order to maintain a good quality of the mesh, the mesh has to be adapted during the simulation, involving particular mesh adaptation techniques. This Lagrangian version of the model has several interesting applications, such as the dynamical mesh refinement along any region of interest (e.g., the ice edge), buoys tracking, or the inclusion of material properties in the rheology.
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| 3-year simulation of the Arctic sea-ice with an adaptive, Lagrangian sea-ice model. Each frame of the video corresponds to one week. The velocity of nodes with an ice thickness below a fixed threshold is set to zero. Note the export and melting of very thick ice through Fram Strait at the begin of the simulation. |
The finite element sea-ice model will benefit from active research in sea-ice modelling in Louvain-la-Neuve for more than 10 years. A new version of the large-scale sea-ice model called LIM3 (Louvain-la-Neuve sea-Ice Model) has been recently released. LIM3 is a C-grid dynamic-thermodynamic model designed for climate studies with subgrid-scale distributions of ice thickness, enthalpy, salt and age (Vancoppenolle et al., 2009a, Vancoppenolle et al., 2009b). The model has been coupled to the French ocean model OPA and is used in numerous European laboratories. In particular, the representation of the ice thickness distribution (ITD) and the halo-thermodynamic model (including the explicit treatment of brine pockets and drainage) will both constitute future developments of the finite element model.