SST subseasonal variability in the central Benguela upwelling system as inferred from satellite observations (1999-2009)

Type Article
Date 2013-09
Language English
Author(s) Goubanova Katerina1, Illig Serena1, Machu Eric2, Garcon Veronique1, Dewitte Boris1
Affiliation(s) 1 : CNRS IRD UPS CNES, Lab Etud Geophys & Oceanog Spatiales, FR-31400 Toulouse, France.
2 : CNRS Ifremer IRD UBO, UMR6523, Lab Phys Oceans, Paris, France.
Source Journal Of Geophysical Research-oceans (0148-0027) (Amer Geophysical Union), 2013-09 , Vol. 118 , N. 9 , P. 4092-4110
DOI 10.1002/jgrc.20287
WOS© Times Cited 30
Keyword(s) Benguela upwelling, satellite observations, intraseasonal variability, wind-SST relationship, mean vertical stratification, Antarctic oscillation
Abstract Subseasonal variability of Sea Surface Temperature (SST) in the central Benguela upwelling system is investigated using TMI satellite-derived data over the period 1999-2009. Spatial patterns and time-frequency characteristics of subseasonal variability are documented based on Empirical Orthogonal Functions (EOF) decomposition and wavelet analysis. Despite the land contamination of the TMI satellite data within approximately 100 km off the coast the first EOF of SST anomalies allows characterizing the coastal upwelling variability at the subseasonal scale. Two regimes of variability are evidenced: a submonthly (2-30 days) regime with a dominant 11 days oscillation and a lower frequency intraseasonal (30-90 days) regime with a dominant 61 days oscillation. Both regimes are modulated, to a large extent, by the local surface wind stress and are consistent with Ekman dynamics. The seasonality of the relationship between wind stress and SST for submonthly (intraseasonal) regime is characterized by a marked semiannual (annual) cycle, which is explained in terms of the impact of seasonal change of the upper ocean stratification on the vertical advection process. The wind-driven SST subseasonal variability is shown to be associated with eastward propagating disturbances in the midlatitudes corresponding to a wave number 4. The results also suggest an important role of the Antarctic Oscillation in modulating the intraseasonal wind-driven SST variability. The characteristics of the equatorial intraseasonal Kelvin waves are documented in order to discuss possible impact of remote oceanic forcing on SST variability along the coast in the Benguela upwelling system.
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Goubanova Katerina, Illig Serena, Machu Eric, Garcon Veronique, Dewitte Boris (2013). SST subseasonal variability in the central Benguela upwelling system as inferred from satellite observations (1999-2009). Journal Of Geophysical Research-oceans, 118(9), 4092-4110. Publisher's official version : https://doi.org/10.1002/jgrc.20287 , Open Access version : https://archimer.ifremer.fr/doc/00164/27565/