THE RIO DE LA PLATA ESTUARY RESPONSE TO WIND VARIABILITY IN SYNOPTIC TO INTRA-SEASONAL SCALES: BAROTROPIC RESPONSE.

SIMIONATO, C. G.; MECCIA, V. L.; DRAGANI, W. C.; GUERRERO, R. A.; NUÑEZ, M. N.

JOURNAL OF GEOPHYSICAL RESEARCH

American Geophysical Union

Lugar: Washington DC, USA; Año: 2006 vol. 111 p. 1 - 14

0148-0227

The first long-period acoustic Doppler current profiler series collected in twolocations of the Rı´o de la Plata estuary are explored for barotropic current variability andits connection to wind variability in synoptic to intraseasonal timescales. Wind-drivencurrents can be explained in terms of two modes, resulting of the estuary’s geometry. Thefirst one prevails for winds with a cross-river component, whereas the seconddominates when they blow along the estuary axis. Even though both modes imply thatbarotropic currents develop in a phase lag with the wind that depends on the location,northeasterly and southwesterly winds generate stronger currents than southeasterly andnorthwesterly winds. Barotropic response to winds occurs in around 6 hours, and anequilibrium regime is reached for processes with temporal scales more than 4 days. Thetemporal scales of estuarine variability replicate the wind ones, with activity in bandsaround 2–8, 10–12, and 18–25 days. Therefore the estuary reaches an equilibrium regimewith most of atmospheric processes from synoptic to intraseasonal scales.Intraseasonal variability can be significant and even act in the same direction as thesynoptic one, with important effects on circulation. These features imply that the estuaryhas ‘‘weather’’ and ‘‘climate’’ as the atmosphere does. Our results suggest thatconditions classically thought as characteristic of ‘‘summer’’ or ‘‘winter’’ likely occurduring any season with high variability. This result has important implications for thosecoastal species that spawn in the estuary, as they require specific conditions for theirsuccessful reproduction, and on estuary’s predictability.