Exploring the observability of high-resolution satellite altimetry with a regional model of the Solomon Sea

Bughsin DJATH (LGGE, CNRS, Grenoble/LEGOS, IRD, Toulouse, France)


Jacques VERRON (LGGE, CNRS, Grenoble, France); Alexandre GANACHAUD (LEGOS, IRD, Toulouse, France); Lionel GOURDEAU (LEGOS, IRD, Toulouse, France); Bernard BARNIER (LGGE, CNRS, Grenoble, France); Jean-Marc MOLINES (LGGE, CNRS, Grenoble, France)

Event: 2014 Ocean Surface Topography Science Team Meeting

Session: Science Results from Satellite Altimetry: Finer scale ocean processes (mesoscale and coastal)

Presentation type: Type Poster

SARAL/Altika is providing improved resolution data for studying mesoscale processes in the ocean. This will be even more valid for SWOT measurements. But with SWOT, there is still much uncertainty on the signal that will be observed, especially at the submesoscales. There are indeed many scientific questions that are unresolved about the observability of altimetry at very high resolution and more generally on the dynamical role of the ocean meso- and submesoscales.

In this work, we propose to use a high-resolution numerical model as a regional laboratory to explore such observability and dynamical issues. It has been set up in the Western Pacific Solomon sea. The Solomon Sea is a semi-closed sea in the subtropical Pacific Ocean. It connects subtropical water masses to the equatorial one through the low latitude western boundary currents and could potentially modulate the tropical Pacific climate at decadal time-scales. In the South West Pacific, the Solomon Sea exhibits the highest levels of eddy kinetic energy but relatively little is known about the mesoscale and submesoscale activities in this region. Besides, its complex and intricate bathymetry because of its narrow straits and numerous islands, raise specific challenges for both model and altimetric data processing.

So far, we set up the Solomon sea model configuration at 1/36° resolution. The model is two-way embedded in a 1/12° regional model which is itself one-way embedded in the DRAKKAR 1/12° global model. The NEMO code is used as well as the AGRIF software for model nesting. Validation is realized by reference to available in situ data. This high resolution numerical model clearly reveal small scale features, eddies, fronts and filaments. First spectral analysis reveals a behavior that is consistent with the SQG theory and there is a clear evidence of energy cascade from the small scales including the submesoscales, although those submesoscales are only partially resolved with the model.

A lot of work is still to be done with this model, the rich and intense variability of which is difficult to analyse. The evidence of submesoscale features is clear and associated to frontogenesis but also to small scale topography effects. It brings some preliminary answers but also may be the basis for future developments such as the addition of tidal effects that are so far only simply parametrized.

Bughsin DJATH
LGGE, CNRS, Grenoble/LEGOS, IRD, Toulouse