@InProceedings{ViannaMene:2002:FuEvTr,
author = "Vianna, Marcio L. and Menezes, Vivian V. de",
title = "Further evidence for a tropical water gyre in the Southwestern
Atlantic",
year = "2002",
organization = "Simp{\'o}sio Brasileiro de Oceanografia, 1.",
keywords = "OCEANOGRAFIA.",
abstract = "Two views for the gyre structure of the upper layer geostrophic
circulation in the southwestern Atlantic Ocean has been presented
in the literature: (i)a single gyre, limited in the north at
10S-15S, and in the south by the Brazil-Malvinas confluence, with
a recirculation cell centered at 35o S, and (ii)a double-gyre
structure, with the northern gyre dominated by a single water
mass, the Salinity Maximum Water (SMW), with about the same
northern limit, but with its southern limb coinciding with a
subtropical front and its associated eastward current at about 28o
S. We discuss evidence favoring the double-gyre view, by focusing
on analysis of new data (ADCP, hydrographic and Topex/ERS
altimeter). Evidence supporting the existence of a strong (50
cm/s)geostrophic eastward current at 28o S, and a Brazil Current
upper layer retroflection near this latitude, is described. This
eastward current reaches depths of 300m, and its dynamics may be
the same as the open-ocean Subtropical Countercurrents of the
north Pacific and Atlantic oceans. Transport estimates will be
presented. The detailed structure of recirculation cells inside
this gyre domain is presented, and its annual cycle described. It
is shown that while variability to the east of the gyre domain is
dominated by Rossby waves, inside its domain the gyre is dominated
by frontal eddies aligned along the 28S-30S quasi-zonal front, by
eddies at the shelf break and possibly by open ocean eddies
related to subsidence of mixed layer water into the thermocline.
The data analysis suggests future research priorities could be
oriented into processes that might explain such complex
interaction patterns between the atmosphere, the upper water
layer, the intermediate layer and the abrupt change in the
coastline, not far from the Brazilian coast, but still further
into the open ocean than present-day programs. It could require a
system of deep sea moorings to study the evolution of the water
column, as was done in the FASINEX program in the north Atlantic.
We may add that biogeographic studies reporting the discovery of
the presence of a strong gradient in zooplankton biodiversity at
that same latitude is suggested as consistent with the existence
of the countercurrent, which also supports a rich tuna fishery
exploited by fishing industry based in the city of
Itaja{\'{\i}}.",
conference-location = "S{\~a}o Paulo",
conference-year = "26-30 ago. 2002",
label = "11380",
targetfile = "vianna.pdf",
urlaccessdate = "27 abr. 2024"
}