Intraseasonal variability of the North Brazil Undercurrent forced by remote winds

• Published in: Journal of Geophysical Research: Oceans
• Main Authors: Veleda, D., Araujo, M., Zantopp, Rainer J., Montagne, R.
• Format: Article in Journal/Newspaper
• Language: English
• Published: AGU (American Geophysical Union) 2012
• Subjects: Austral; South Atlantic Ocean
• Online Access: https://oceanrep.geomar.de/id/eprint/19254/; https://oceanrep.geomar.de/id/eprint/19254/1/2012JC008392-pip.pdf; https://oceanrep.geomar.de/id/eprint/19254/7/Veleda_et_al-2012-Journal_of_Geophysical_Research__Oceans_%281978-2012%29.pdf; https://doi.org/10.1029/2012JC008392

Intraseasonal signals with periods of 2 to 3 weeks in near-surface alongshore current measurements are detected from four moorings (K1 - K4) deployed from 2000 to 2004 at the 11{degree sign}S section close to the Brazilian coast as part of the German CLIVAR Tropical Atlantic Variability Project. This section crosses the path of the North Brazil Undercurrent, the most powerful western boundary current in the South Atlantic Ocean. We investigate the origin of this intraseasonal variability of the North Brazil Undercurrentby relating the oceanic oscillation of the alongshore currents to its atmospheric counterpart, the meridional wind stress. On average, the results indicate a well-defined lagged (10 days) correlation (~0.6) structure between meridional wind stress and alongshore currents. The oceanic region with the highest cross-correlations is identified as a relatively narrow band along the Brazilian coast, from 22{degree sign}-36{degree sign}S and 40{degree sign}-50{degree sign}W, bounded in the north by an eastward change in coastline orientation. The cross-wavelet transform establishes the common power between the time series of meridional wind stress and alongshore currents, predominantly during austral winter and spring. These signals propagate equatorward with an alongshore speed of 285{plus minus}63 km day-1, consistent with Coastal Trapped Wave theory.