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Ocean Dynamics

, Volume 65, Issue 2, pp 173–186 | Cite as

Observed year-to-year sea surface salinity variability in the Bay of Bengal during the 2009–2014 period

  • Akurathi Venkata Sai Chaitanya
  • Fabien Durand
  • Simi Mathew
  • Vissa Venkata Gopalakrishna
  • Fabrice Papa
  • Matthieu Lengaigne
  • Jerome Vialard
  • Chanda Kranthikumar
  • R. Venkatesan
Article

Abstract

The present study describes the observed sea surface salinity (SSS) interannual variability in the Bay of Bengal over the 2009–2014 period. It is based on an original compilation of all available in situ SSS observations in that region, assembled in a 2°-resolution trimonthly gridded field. We find that year-to-year SSS variability is particularly strong in the north-eastern part of the bay. Over recent years, this variability takes the form of two successive and opposite phases: a saltening phase from mid-2009 to late 2010, immediately followed by a freshening phase from late 2010 to late 2011. The typical magnitude of each anomalous spell is about one in the practical salinity scale, making this area one of the most variable of the tropical oceans at interannual timescales. A simple mixed-layer salt budget indicates that year-to-year large-scale SSS variability in the Northern Bay of Bengal is primarily driven by freshwater flux variability with a correlation of 0.68, with rather independent contributions from precipitation and river run-off. The oceanic surface circulation variability contributes less systematically to the large-scale SSS evolution in the Northern Bay of Bengal over the entire record with a correlation of 0.13, despite a strong contribution at times, in particular, during the 2011 positive Indian Ocean Dipole (IOD) freshening.

Keywords

SSS Bay of Bengal Argo Ganges Brahmaputra IOD 

Notes

Acknowledgments

We thank the three anonymous reviewers for their constructive comments on our paper. XCTD and bucket salinity observations are supported by the Ministry of Earth Sciences, through the Indian National Center for Ocean Information Services, Hyderabad, India. We thank the numerous people who spent a long time at sea collecting the salinity observations. Thermosalinograph data were collected and processed by the French SSS Observation Service (www.legos.obs-mip.fr/observations/sss). We sincerely thank the team efforts of NIOT technical and scientific staff for providing continuous data from the OMNI moorings. We are thankful to Argo and RAMA programmes for making their salinity data available to all. FD, FP, ML and JV are funded by Institut de Recherche pour le Développement (IRD). Part of this work was done when CAVS and FD visited the Indo-French Cell for Water Sciences (Joint International Laboratory IRD-IISc, Bangalore, India). Support from this laboratory is gratefully acknowledged. We acknowledge constructive comments by Debasis Sengupta. This is CSIR-NIO contribution No. 5689

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Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  • Akurathi Venkata Sai Chaitanya
    • 1
  • Fabien Durand
    • 1
    • 2
  • Simi Mathew
    • 4
  • Vissa Venkata Gopalakrishna
    • 1
  • Fabrice Papa
    • 2
    • 3
  • Matthieu Lengaigne
    • 5
    • 6
  • Jerome Vialard
    • 5
  • Chanda Kranthikumar
    • 1
  • R. Venkatesan
    • 4
  1. 1.CSIR/National Institute of Oceanography (NIO)GoaIndia
  2. 2.IRD/Laboratoire d’études en Géophysique et Océanographie Spatiales (LEGOS)ToulouseFrance
  3. 3.Indo-French Cell for Water Sciences, IISc-NIO-IITM–IRD Joint International Laboratory, IIScBangaloreIndia
  4. 4.National Institute of Ocean Technology (NIOT)ChennaiIndia
  5. 5.Sorbonne Universités, UPMC Univ Paris 06, UMR 7159, LOCEANParisFrance
  6. 6.Indo-French Cell for Water SciencesNational Institute of OceanographyDona PaulaIndia

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