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Caractéristiques des Masses d'Eau, Transport de masse et Variabilité de la circulation océanique en mer de Corail

Florent Gasparin 1
1 OLVAC - Océan du Large et Variabilité Climatique
LEGOS - Laboratoire d'études en Géophysique et océanographie spatiales
Abstract : Waters from the South Equatorial Current, the northern branch of the South Pacific subtropical gyre, have been identified as having an important contribution to climate variability and El Niño-Southern Oscillation. Initially a broad westward current extending from 2°S to 30°S, the South Equatorial Current splits upon the major archipelagos of Fiji (18°S, 180°E), Vanuatu (16°S, 168°E), New Caledonia (22°S, 165°E) and Australian coasts resulting in two main zonal jets entering the Coral Sea: the North Caledonian Jet (18°S, 180°E) and the North Vanuatu Jet (16°S, 168°E). In this work, we focus on the oceanic circulation using hydrographic data from sea cruises and we apply two inverse methods: the "inverse box model" and the "optimal multi-parametric analysis". Then, we report interannunal variability and its impacts on the Coral Sea circulation. We first study the East Caledonian Current which runs along the east coast of New Caledonia and feeds the North Caledonian Jet. Both currents extend about 100 km horizontally, to at least 1000 m depth vertically and transport 15 Sv (1 Sv = 106 m3.s-1). In the northern part, the North Vanuatu Jet is larger (∼300 km) and shallower (0-500 m) and transports around 20 Sv. A part of these waters reaches Australia and supplies the Solomon Sea via its western boundary current, the New Guinea Coastal Undercurrent estimated at 30 Sv. These structures are characterized by water mass properties. Secondly, we emphasize the thermocline and intermediate waters to depict water mass pathways and mixing. In the thermocline, the New Guinea Coastal Undercurrent is mainly supplied by North Vanuatu Jet waters at the thermocline level while in the intermediate level, waters come from the North Caledonian Jet. This complementary approach shows that intermediate waters are mainly carried by deep currents and subsurface waters by the North Vanuatu Jet. In the last part, interannual variability is analyzed on the 1993-2010 period with a 1/10° numerical simulation and a proxy method based on altimetric data. Interannual variability of the South Equatorial Current mass transport follows the El Niño-Southern Oscillation with a 3-months lag. The North Vanuatu Jet leads this variability. Controlled by winds, the South Equatorial Current variability is associated with thermocline depth modulation, which involves intensification after an El Niño event (6 ±4 Sv) and a decrease after La Niña (4 ±4 Sv). We also show that temperature and salinity anomalies are the result of thermocline depth modulation. This work increases the understanding of the regional circulation and suggests new focus to depict the southwest Pacific circulation.
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Submitted on : Wednesday, July 3, 2013 - 11:52:39 AM
Last modification on : Thursday, October 15, 2020 - 3:15:03 AM
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  • HAL Id : tel-00840821, version 1

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Florent Gasparin. Caractéristiques des Masses d'Eau, Transport de masse et Variabilité de la circulation océanique en mer de Corail. Océanographie. Université Paul Sabatier - Toulouse III, 2012. Français. ⟨tel-00840821⟩

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