Brazil Malvinas Frontal System as seen from 9 years of advanced very high resolution radiometer data

Abstract

[1] Surface thermal fronts in the southwestern Atlantic (SWA) Ocean are examined using 9 years (1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995) of advanced very high resolution radiometer data. Fronts are detected considering a gradient based edge detector. Sea surface temperature gradients are calculated from 4 km resolution 5-day composite images covering the western Argentine Basin south of 30°S. Variability in the position and intensity of the fronts from seasonal to interannual timescales is characterized in six regions including different parts of the Brazil Current Front (BCF) and the Subantarctic Front (SAF): Shelf Break-Brazil (SB-B), Brazil Malvinas Collision (BM-C), Brazil Current-Overshoot (BC-O), Shelf BreakMalvinas (SB-M), Malvinas Return Flow (MRF), and Falkland Escarpment (FE). Fronts in the SB-B, SB-M, MRF, and FE regions are controlled by the bathymetry. In the BM-C region the BCF and SAF appear to merge as a single front. This front does not present large seasonal north-south excursions as previously described, though it pivots seasonally around a fixed point located approximately at 39.5°S, 53.5°W, changing its orientation from N-S in winter to NW-SE in summer. Consequently, on average, the front intersects the 1000 m isobath at 38°30 0 S in summer and north of 37°S in winter. In the BC-O region the BCF has a U-shape centered at 53°W. The intensity of the fronts in each region except in the FE region presents large seasonal variability. In the SB-B, BM-C, and BC-O regions the frontal intensity is highest (>0.35°C/km) during austral winter, the annual components explain 83, 67, and 71% of the total variance, respectively. In the SB-M and MRF regions the SAF is most intense (>0.25°C/km) in summer and fall; the annual component of the intensity fluctuations explains 29 and 38% of the total variance, respectively. In the FE region the annual component of frontal intensity explains only 17% of the variability. In the six regions, important interannual variability is found. The Zapiola Rise (centered at 45°S, 43°W) appears as a gradient-free region. Closed planetary potential vorticity contours in this area suggest it is dynamically isolated.

Structure of the seabird assemblage associated with pelagic longline vessels in the southwestern Atlantic: implications for bycatch

“…1). The principal oceanographic characteristic of this zone is the occurrence of the BMC formed by the confluence of the Brazilian Current and the Malvinas Current (Olson et al 1988, Seeliger et al 1998, Goni & Wainer 2001, Acha et al 2004, Saraceno et al 2004, Ortega & Martínez 2007. The confluence region of these 2 currents exhibits complex movements of fronts and the simultaneous presence of warm and cold eddies.…”

“…The southwest Atlantic Ocean is a region characterized by the confluence of the Brazilian Current and the Malvinas Current (i.e. Brazil-Malvinas Confluence, BMC), which generates numerous superficial and sub-superficial fronts (Olson et al 1988, Goni & Wainer 2001, Saraceno et al 2004). The high concentration of prey species (Acha et al 2004) and the aggregation of fisheries resources of commercial interest along these fronts leads to the overlap of industrial fisheries with albatross and petrel species (Veit 1995, Acha et al 2004, Favero & SilvaRodríguez 2005.…”

Remote sensing of coccolithophore blooms in selected oceanic regions using the PhytoDOAS method applied to hyper-spectral satellite data

“…The Patagonian Shelf, between 38 • S and 51 • S, is located southwest of the confluence zone and therefore is affected by that. Apart from that, according to hydrography observations and satellite imagery (Saraceno et al, 2004;Bianchi et al, 2005;Romero et al, 2006), there are two other factors affecting the hydrography of the Patagonian Shelf: the shelf break front, which is a transition between the Malvinas current and shelf waters, existing in both winter and summer seasons (being stronger in the summer months) and the energetic tidal fronts, with pronounced seasonal variability, causing the vertical stratification of water masses (Sabatini et al, 2004;Bianchi et al, 2005). such as the characteristic of the warm poleward waters of the East Australian Current (EAC) (Cai et al, 2005;Ridgway, 2007).…”

Acharadria crocea (Cnidaria: Hydrozoa): estudo integrado da ecofisiologia do assentamento larval e modelagem de nicho ecológico

“…A dinâmica de correntes marinhas da costa da América do Sul não favorece a primeira hipótese, uma vez que a Corrente do Brasil é predominante durante o verão, e mantém as águas costeiras muito aquecidas, fornecendo uma barreira para a dispersão das larvas que viriam do sul. Já no inverno, a convergência da Corrente do Brasil com a Corrente das Malvinas se dá mais ao norte do que no verão (Saraceno et al 2004) porém, esta é a época que as colônias estão menos reprodutivas na Argentina, igualmente diminuindo o potencial de recolonização. Além disso, a ausência de substratos consolidados ao longo de uma extensa área no Estado do Rio Grande do Sul oferece uma barreira adicional ao transporte das larvas actínulas, que não apresentam vida longa no plâncton (Todd 1998).…”