Climatic variability in the vicinity of Wallis, Futuna, and Samoa islands (13°–15° S, 180°–170° W)
1999; EDP Sciences; Volume: 22; Issue: 3 Linguagem: Inglês
10.1016/s0399-1784(99)80050-4
ISSN1878-4143
Autores Tópico(s)Oceanographic and Atmospheric Processes
ResumoMean conditions, seasonal, and ENSO-related (El Nifio Southern Oscillation) variability in the vicinity of Wallis, Futuna, and Samoa islands (13"-1.5"S, 180"-170" W) over the 1973-1995 period are analysed for wind pseudostress, satellite-derived and in situ precipitation, sea surface temperature (SST) and salinity (SSS), sea level, and O-450 m temperature and geostrophic current.The mean local conditions reflect the presence of the large scale features such as the western Pacific warm pool, the South Pacific Convergence Zone (SPCZ), and the South Pacific anticyclonic gyre.The seasonal changes are closely related to the meridional migrations of the SPCZ, which passes twice a year over the region of study.During the warm phase of ENS0 (El Niiio), we generally observe saltier-than-average SSS (of the order of 0.4), consistent with a rainfall deficit (0.4 m yi'), a hint of colder-than-average surface temperature is also identified in subsurface (0.3 "C), a weak tendency for westward geostrophic current anomalies (2 cm s-l at the surface), a sea level decrease (5-10 cm), together with easterly (5 m2 s-*) and well marked southerly (10 m* s-*) wind pseudo-stress anomalies.Anomalies of similar magnitude, but of opposite sign, are detected during the cold phase of ENS0 (La Nina).While these ENSO-related changes apply prior to the 1990s they were not observed during the 1991-1994 period, which appears atypical.0 Elsevier, Paris / Ifremer / Cnrs / Ird Wallis and Futuna / Samoa / El Nifio Southern Oscillation / climatic variability R&urn6 -VariabilitC climatique au large des iles Wallis, Futuna et Samoa (13"-15" S, MO"-170" W).Les conditions climatiques moyennes, les variations saisonnibres et interannuelles associees au phenomene El Niiio Oscillation Australe (ENOA) de la region situee au voisinage des iles Wallis, Futuna et Samoa (13"-15" S, 180"-170" W) sont d&rites pour les annees 1973-1995.Les parametres analyses comprennent la pseudo-tension du vent, les precipitations (estimations satellitales et mesures in situ), la temperature et la salinitt de surface, le niveau de lamer, les profils verticaux O-450 m de temperature et de courant geostrophique.Pour l'ensemble des parambtres, les conditions moyennes traduisent la presence des structures a grandes Cchelles du Pacifique tropical, a savoir les eaux chaudes (>28 "C) du Pacifique ouest, la zone de convergence des vents et le grand tourbillon anticyclonique du Pacifique sud.Les variations saisonnieres sont pour l'essentiel likes a la migration nord-sud de la zone de convergence du Pacifique sud qui passe deux fois par an sur la region d'ttude.Au tours de la phase chaude du phenomene ENOA (El Nifio), on observe en general une salinite superieure a la normale (de l'ordre de 0,4), cohtrente avec une baisse des precipitations (-0,4 m an-'), une tendance au refroidissement des eaux de surface et de subsurface (-0,3 "C), une anomalie de courant geostrophique dirigee vers l'ouest (-2 cm s-' a la surface), une baisse du niveau de la mer (-5 a -10 cm), ainsi qu'une diminution moderee de la composante est-ouest des alizes (-5 m* s2) et un renforcement marqut de la composante sud-nord (+lO m2 sm2).Les anomalies observtes au tours de la phase chaude
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