000K  utf8
1100  $c2020
1500  eng
2050  urn:nbn:de:gbv:8-mods-2020-00151-7
3000  Schubert, René
4000  Der Einfluss Submesoskalischer Strömungen auf die Mesoskalische Agulhas Dynamik$hChristian-Albrechts-Universität zu Kiel  [Schubert, René]
4000  The Impact of Submesoscale Flows on Mesoscale Agulhas Dynamics$hChristian-Albrechts-Universität zu Kiel  [Schubert, René]
4030  Kiel$nChristian-Albrechts-Universität zu Kiel
4209  Mesoscale eddies are central to the oceanic circulation and the global climate. Of particular importance, in this respect, are mesoscale eddies in the Agulhas region south of Africa, as they govern the inflow of warm and salty Indian Ocean waters into the Atlantic Ocean. In this dissertation, it is shown that these eddies are strengthened by submesoscale flows. This highlights the importance of including submesoscale effects for a realistic representation of the mesoscale dynamics in ocean models. First, a general circulation ocean model for the Agulhas region is improved with respect to the simulation of submesoscale dynamics by increasing the vertical and horizontal resolution and reducing the model diffusion and dissipation. Second, a model validation based on horizontal-wavenumber spectra computed from high-resolution satellite sea-surface temperature and sea-surface height measurements is performed. It demonstrates that the simulated submesoscale and mesoscale circulation in the Cape Basin are extraordinary well represented in this model. A comparison to two parallel model experiments, of which the first only resolves the largest and the second no submesoscale flows, reveals that the mesoscale spectral density of sea-surface height increases the more submesoscales are resolved. The results of an eddy detection algorithm show that this can be attributed to a strengthening of the mesoscale eddies. Third, a coarse-graining approach for the transfer of kinetic energy between spatial scales is applied to the model outputs. The results indicate that the mesoscale eddies are strengthened in spring or early summer by the absorption of submesoscale eddies resulting from baroclinic mixed-layer instability in winter. Fourth, this analysis complemented with the computation of the transfer of kinetic energy between temporal scales reveals that submesoscale eddies emerging from barotropic instabilities at the northern boundary of the Agulhas Current are important for the strength of shear-edge eddies and further of lee cyclones that propagate into the Cape Basin. The model comparison shows that the combination of both strengthening effects contributes to an increase of the surface mesoscale kinetic energy in the Cape Basin by 28 %, if submesoscale processes are resolved.
4950  https://nbn-resolving.org/urn:nbn:de:gbv:8-mods-2020-00151-7$xR$3Volltext$534
4961  https://macau.uni-kiel.de/receive/macau_mods_00000504
5051  500
5550  Agulhas
5550  Dynamics
5550  Eddies
5550  Ocean
5550  Submesoscale