Vera Fofonova

FESOM-C: coastal dynamics on hybrid unstructured meshes

We describe FESOM-C, the coastal branch of the Finite-volumE Sea ice – Ocean Model (FESOM2), which shares with FESOM2 many numerical aspects, in particular, its finite-volume cell-vertex discretization. Its dynamical core differs by the implementation of time stepping, the use of terrain-following vertical coordinate and formulation for hybrid meshes composed of triangles and quads. The first two distinctions were critical for coding FESOM-C as an independent branch. The hybrid mesh capability improves numerical efficiency, since quadrilateral cells have fewer edges than triangular cells. They do 5 not suffer from spurious inertial modes of the triangular cell-vertex discretization and need less dissipation. The hybrid mesh capability allows one to use quasi-quadrilateral unstructured meshes, with triangular cells included only to join quadrilateral patches of differt resolution or instead of strongly deformed quadrilateral cells. The description of the model numerical part is complemented by test cases illustrating the model performance.

Russian – German Cooperation in the Siberian Arctic (LenaDNM Project) – a Preface -

1 Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, D-25992 List, Germany. The Arctic Ocean and its shallow but extensive marginal shelf-seas are a significant component in understanding the global climate system and its modern change. The sea-ice covered polar shelf seas, over vast areas supported by submarine permafrost and affected by strong freshwater input from fluvial discharge, form a very unique environment of land– ocean–interaction along the Arctic coasts. They form a vast border zone between warmer freshwater continental runoff and the colder currents of the Arctic Ocean. This is particularly the case for the Siberian Arctic Shelf (SAS) which includes the Kara, Laptev and East Siberian seas. The SAS is a wide and relatively shallow area, with an average depth of about only 30 to 40 m, and a complex oceanographic and biogeochemical regime, which is influenced by a huge freshwater input from the Siberian rivers e.g., Kassens et al. (1999), stein et al. (2003), DmitrenKo et al. (2005).