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Titel |
Modelling the ocean around South Africa: Interactions between the Agulhas Current and the ACC |
VerfasserIn |
J. Kuhlmann, H. Dobslaw, M. Thomas, C. Petrick |
Konferenz |
EGU General Assembly 2012
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 14 (2012) |
Datensatznummer |
250058752
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Zusammenfassung |
Regional ocean models are extraordinarily useful tools as complements to global models,
since they work at higher spatial and temporal resolutions and parameters can be
adapted to the particular conditions in the region of interest. These advantages are
bought with new potential issues at the boundaries of the modelled region. At open
boundaries, a global model has to provide boundary conditions such as velocity,
temperature, and salinity, necessarily obtained at coarser resolution and with less
accuracy.
The region we focus on is the surroundings of South Africa, comprising parts of
the Southern Atlantic and Southern Indian Ocean as well as the Southern Ocean
down to the ice shelves of Antarctica. We attempt to better understand the dynamics
of the Agulhas Current, which has been shown to have far-reaching impacts also
on the Meridional Overturning Circulation and, thereby, on the world’s climate.
With our study region expanded southwards, including a fraction of the Antarctic
Circumpolar Current (ACC), we investigate the local current-current interactions which are
conveyed by small-scale turbulences. In our analysis, we focus on sea surface height
and ocean bottom pressure and the different forcing terms that influence these two
variables.
We configure a version of the Regional Ocean Modelling System (ROMS) to
simulate ocean dynamics around South Africa, forced with ERA-Interim atmospheric
data, and explore the sensitivity to various choices of boundary conditions. The
horizontal resolution of 0.25°Ã0.25° at 32 vertical levels is supposed to resolve
mesoscale eddies as well as the climatologically important shedding of Agulhas
rings. To show the capabilities of our model, we compare the output in terms of
sea-surface heights to altimetric measurements provided by AVISO. In-situ data of ocean
bottom pressure measured in the ACC path adds to the observational database.
The study area is especially promising as, additionally, we can show whether the
simulations of an integrated ocean bottom pressure signal correspond to the residuals in
measurements of the Superconducting Gravimeter in Sutherland, South Africa. |
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