The connection of the Indonesian Throughflow, South Indian Ocean Countercurrent and the Leeuwin Current
East of Madagascar, the shallow “South Indian Ocean Counter Current (SICC)” flows from west to east across the Indian Ocean against the direction of the wind-driven circulation. The SICC impinges on west Australia and enhances the sea level slope, strengthening the alongshore coastal jet: the Leeuwi...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-06-01
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| Series: | Ocean Science |
| Online Access: | http://www.ocean-sci.net/12/771/2016/os-12-771-2016.pdf |
| Summary: | East of Madagascar, the shallow “South Indian Ocean Counter Current (SICC)”
flows from west to east across the Indian Ocean against the direction of the
wind-driven circulation. The SICC impinges on west Australia and enhances the
sea level slope, strengthening the alongshore coastal jet: the Leeuwin
Current (LC), which flows poleward along Australia. An observed transport
maximum of the LC around 22° S can likely be attributed to this
impingement of the SICC. The LC is often described as a regional coastal
current that is forced by an offshore meridional density gradient or sea
surface slope. However, little is known about the controls of these open-ocean
gradients. The regional circulation system is embedded in the
subtropical “super gyre” that connects the Indo-Pacific via the Tasman
Gateway and the Indonesian passages. The Indonesian Throughflow (ITF)
circulates through the Indian Ocean back into the Pacific south of Australia.
This return pathway appears to be partly trapped in the upper layer north of
an outcrop line. It is redirected along this outcrop line and joins the
eastward flow of the SICC. To study the connection of the basin-scale and the
inter-ocean-scale dynamics, we apply both an ocean general circulation model
and a conceptual two-layer model. Shutdown of the ITF in the models leads to
a large decrease in Leeuwin Current transport. Most of the SICC was found to
then reconnect to the internal gyre circulation in the Indian Ocean. ITF,
SICC and LC thus appear to be dynamically connected. |
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| ISSN: | 1812-0784 1812-0792 |