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Title

A 3D view of the Brazil-Malvinas frontal system

AuthorsRosell Fieschi, Miquel ; Isern-Fontanet, Jordi ; Emelianov, Mikhail ; Saraceno, Martin; Valla, Daniel; Salvador, Joaquín ; Fernández Gallego, Pedro; Pelegrí, Josep Lluís
Issue Date23-May-2016
Citation48th Liège Colloquium: Submesoscale Processes. Mechanisms, Implications and New Frontiers (2016)
AbstractIn March 2015, the R/V Hespérides carried out the TIC-MOC cruise, a 14-day oceanographic expedition in the Brazil-Malvinas Confluence (BMC) region. One principal objective of this cruise was to characterize the fine structure of the frontal system (or front) between the subtropical and subantarctic waters. The surface position of the front (sea-surface front) was determined in near-real time using sea surface temperature (SST), color and altimetry data, as well as daily outputs from the operational Mercator global-ocean analysis and forecast system at 1/12 resolution. A total of 66 hydrographic stations were carried out and nine drifters were deployed. Additionally, seven Argo profilers (vertical cycles of either 5 or 10 days) were launched, which meant an additional 19 conductivity-temperature-depth (CTD) profiles down to 2000 m simultaneous with the cruise, and another two APEX profilers were left to drift in the region before their recovery, representing another 42 CTD profiles sampling the top 300-800 m of the water column. The vessel also sampled continuously the sea-surface temperature, salinity and fluorescence, and the velocity fields down to about 600 m, during a total of 11 crossings of the surface front. Here we pay special attention to the description of the front, with 37 hydrographic stations along six cross-frontal sections about 100 km long and down to at least 400 m plus all the CTDs from the APEX profilers, which are combined with a sequence of simultaneous high-resolution (1 km) SST images. The front is formed by the subantarctic waters intruding below the subtropical waters, with horizontal gradients of up to 20 degrees C in about 10 km at 50 m depth. The front steepens as both the Malvinas and Brazil Currents get deflected east, reaching a maximum slope of about 200 m in 50 km at distances less than 150 km from the initial colliding point. We observed numerous thermohaline intrusions (thickness about 10-50 m and width of the order of 10 km) that intrude several tens of km into both sides of the frontal system. The sea-surface front is very sharp in temperature but appears distorted in salinity because of the presence of a filament that carries brackish waters from Rio de la Plata. On its onshore end, the filament is rather wide (up to 100 km) and lays on the subtropical side of the front but, as it moves further offshore, it thins out (down to only a few km), moves towards the surface front and accelerates, reaching speeds close to 2 m s-1, much faster than expected if the flow was in geostrophic balance
Description48th Liège Colloquium: Submesoscale Processes. Mechanisms, Implications and New Frontiers, 23-27 May 2016, Liège, Belgium.-- 1 page, 7 figures
Publisher version (URL)https://dx.doi.org/10.13140/RG.2.1.4971.6721
http://gher-diva.phys.ulg.ac.be/PresentationManager/ILC2016/
URIhttp://hdl.handle.net/10261/161831
Identifiersdoi: 10.13140/RG.2.1.4971.6721
Appears in Collections:(ICM) Comunicaciones congresos
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