Intraseasonal variability of the North Brazil Undercurrent forced by remote winds

• Published in: Journal of Geophysical Research: Oceans 2012-11, Vol.117 (C11), p.n/a
• Main Authors: Veleda, D., Araujo, M., Zantopp, R., Montagne, R.
• Format: Article
• Language: English
• Subjects: alongshore currents; coastal trapped waves; Earth sciences; Earth, ocean, space; equatorward propagation; Exact sciences and technology; intraseasonal variability; Marine; North Brazil Undercurrent; remote wind forcing
• ISSN: 0148-0227; 2169-9275; 2156-2202; 2169-9291
• DOI: 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°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 Undercurrent by 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°–36°S and 40°–50°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 ± 63 km day−1, consistent with Coastal Trapped Wave theory. Key Points Intraseasonal signals in the NBUC Interaction between internal waves and remote winds Coastal trapped waves propagating toward the equator