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Large scale SSS inter-annual variability in tropical Indian and Pacific Oceans

Large scale SSS inter-annual variability in tropical Indian and Pacific Oceans. J. Boutin 1 , O. Hernandez 1 , N. Martin 1 , G. Reverdin 1 , F. Gaillard 2 , S. Morrisset 1 1 CNRS/LOCEAN (CNRS-UPMC-IRD) Paris, France 2 IFREMER/LPO (CNRS-Ifremer-IRD-UBO), Plouzané, France

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Large scale SSS inter-annual variability in tropical Indian and Pacific Oceans

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  1. Large scale SSS inter-annual variability in tropical Indian and Pacific Oceans J. Boutin1, O. Hernandez1, N. Martin1, G. Reverdin1, F. Gaillard2, S. Morrisset1 1 CNRS/LOCEAN (CNRS-UPMC-IRD) Paris, France 2 IFREMER/LPO (CNRS-Ifremer-IRD-UBO), Plouzané, France + collaborations with French GLOSCAL SMOS Cal/Val project QWG10, Boutin & Hernandez

  2. Introduction 2010  : Strong la Niña and negative phase of the Indian Ocean Dipole (IOD) Strong la Niña -IOD These events are known to generate large scale SSS anomalies in the tropics (e.g. Gouriou et Delcroix, 2002, Singh et al. 2011, Grunseich et al. 2011) QWG10, Boutin & Hernandez

  3. Data & Methods DATA: SMOS SSS ESA v5 reprocessing; monthly maps averaged as in (Boutin et al., TGRS, 2012) ARGO + TSG OPTIMAL INTERPOLATED SSS MAPS (ISAS) Monthly maps from In-Situ Analysis System v6 (F. Gaillard, LPO/IFREMER, pers. Comm.) http://wwz.ifremer.fr/lpo/SO-Argo/Products/Global-Ocean-T-S SEA SURFACE AUTONOMOUS DRIFTERSSS Upper S at 45cm depth; Pacific Gyre drifter (Reverdin and Morrisset, LOCEAN) http://www.locean-ipsl.upmc.fr/smos/drifters METHOD: COMPARISON OF SSS ANOMALIES BETWEEN 2010 AND 2011 AS DERIVED BY ISAS AND BY SMOS QWG10, Boutin & Hernandez

  4. High contrasted SSS signal between 2010 and 2011 July 2011-2010 November 2011-2010 • Good consistence between SMOS 2011-2010 SSS differences and ISAS 2011-2010 SSS differences • In the Pacific Ocean, 2011 - 2010 SSS differences associated with displacement of the ITCZ and SPCZ QWG10, Boutin & Hernandez

  5. High contrasted SSS signal between 2010 and 2011 July 2011-2010 November 2011-2010 + - + + - + SSS Anomaly (1975 – CLM ) • Good consistence between SMOS 2011-2010 SSS differences and ISAS 2011-2010 SSS differences • In the Pacific Ocean 2011 - 2010 SSS differences associated with displacement of the ITCZ and SPCZ • In the Indian Ocean : SSS differences consistent with SSS anomalies reported during negative IOD coupled with Strong La niña event (Grunseich et al. 2011) QWG10, Boutin & Hernandez Grunseich et al. 2011

  6. High contrasted SSS signal between 2010 and 2011 July 2011-2010 November 2011-2010 + - + + - + SSS Anomaly (1975 – CLM ) • Good consistence between SMOS 2011-2010 SSS differences and ISAS 2011-2010 SSS differences • 2011 - 2010 SSS differences associated with displacement of the ITCZ and SPCZ • In the Indian Ocean : SSS differences consistent with SSS anomalies reported during negative IOD coupled with Strong La niña event (Grunseich et al. 2011) + - + QWG10, Boutin & Hernandez Grunseich et al. 2011

  7. At first order good consistency in SMOS and ISAS 2011-2010 variability but... July 2011-July2010 November 2011-November 2010 ISAS SMOS Larger contrasts on SMOS SSS anomalies than on ISAS SSS anomalies Why? effect of ARGO/TSG undersampling (=> OI smoothing) and/or a systematic underestimate of SMOS SSS in low SSS/rainy/stratified regions? QWG10, Boutin & Hernandez

  8. 2011-2010 SSS in N. Trop. Pac. (5°N-15°N) SSS anomaly July 2011-2010 SSS July 2010 ISAS SMOS Larger westward extent of the fresh SSS as seen by SMOS than by ARGO : stratification or ARGO undersampling? QWG10, Boutin & Hernandez

  9. 2011-2010 SSS in 30°S-0°N region July 2011-July2010 ISAS SMOS Larger contrasts on SMOS SSS anomalies than on ISAS SSS anomalies QWG10, Boutin & Hernandez

  10. 2011-2010 SSS in 30°S-0°N region July 2011-July2010 July2010 ISAS SMOS Larger contrasts on SMOS SSS anomalies than on ISAS SSS anomalies Fresh region in 2010 fresher on SMOS than ISAS and very few ARGO in fresh region QWG10, Boutin & Hernandez

  11. June 2010 SSS in 30°S-0°N regionSurface autonomous drifter (S at 45cm depth) June 2010 SSS ISAS ISAS MONTHLY SSS SMOS SMOS MONTHLY DRIFTER Again fresh region in 2010 fresher in SMOS than in ISAS maps QWG10, Boutin & Hernandez

  12. Summary • At first order, strong 2011-2010 SSS interannual variability in tropical oceans consistently seen by SMOS and ARGO  • At first order, in the Pacific Ocean, strong 2011-2010 SSS differences associated with displacement of the ITCZ and SPCZ during La Niña event ; in the Indian Ocean : SSS differences consistent with SSS anomalies already reported during negative IOD coupled with Strong La Niña event • 1°x1° 10 days & monthly SMOS SSS (1cm depth) fresher than ARGO & ISAS SSS (~5m depth) in rainy regions : 2 hypothesis: • surface stratification and rain effect • In situ undersampling and OI smoothing • To go further: • -apply a similar smoothing to SMOS and ARGO measurements • -look at 2012... QWG10, Boutin & Hernandez

  13. QWG10, Boutin & Hernandez

  14. EXTRA SLIDES QWG10, Boutin & Hernandez

  15. SSS SMOS Precipitation impact on large scale SSS variability November 2011-2010 ? • 2011 - 2010 SSS differences associated with displacement of the ITCZ and rainy regions • In the Indian Ocean : Saltier SSS in 2010 associated with smaller rain rate during preceding month • High anomaly around Madagascar not consistent with rainy events. RAIN RATE October 2011-2010 ? November 2011-2010

  16. Lower SSS on SMOS than on ISAS when Rain Rate increased

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