Climate Dynamics

, Volume 46, Issue 7–8, pp 2633–2655 | Cite as

Intraseasonal variability of mixed layer depth in the tropical Indian Ocean

  • M. G. Keerthi
  • M. Lengaigne
  • K. Drushka
  • J. Vialard
  • C. de Boyer Montegut
  • S. Pous
  • M. Levy
  • P. M. Muraleedharan


In this paper, we use an observational dataset built from Argo in situ profiles to describe the main large-scale patterns of intraseasonal mixed layer depth (MLD) variations in the Indian Ocean. An eddy permitting (0.25°) regional ocean model that generally agrees well with those observed estimates is then used to investigate the mechanisms that drive MLD intraseasonal variations and to assess their potential impact on the related SST response. During summer, intraseasonal MLD variations in the Bay of Bengal and eastern equatorial Indian Ocean primarily respond to active/break convective phases of the summer monsoon. In the southern Arabian Sea, summer MLD variations are largely driven by seemingly-independent intraseasonal fluctuations of the Findlater jet intensity. During winter, the Madden–Julian Oscillation drives most of the intraseasonal MLD variability in the eastern equatorial Indian Ocean. Large winter MLD signals in northern Arabian Sea can, on the other hand, be related to advection of continental temperature anomalies from the northern end of the basin. In all the aforementioned regions, peak-to-peak MLD variations usually reach 10 m, but can exceed 20 m for the largest events. Buoyancy flux and wind stirring contribute to intraseasonal MLD fluctuations in roughly equal proportions, except for the Northern Arabian Sea in winter, where buoyancy fluxes dominate. A simple slab ocean analysis finally suggests that the impact of these MLD fluctuations on intraseasonal sea surface temperature variability is probably rather weak, because of the compensating effects of thermal capacity and sunlight penetration: a thin mixed-layer is more efficiently warmed at the surface by heat fluxes but loses more solar flux through its lower base.


Mixed Layer Depth Outgoing Longwave Radiation Buoyancy Flux Mixed Layer Depth Variation Mixed Layer Depth Variability 



Microwave OI SST data are produced by Remote Sensing Systems and sponsored by National Oceanographic Partnership Program (NOPP), the NASA Earth Science Physical Oceanography Program, and the NASA MEaSUREs DISCOVER Project. Data are available at Model experiments were performed using HPC resources from GENCI-IDRIS (Grant 2010-011140). Jérôme Vialard and Matthieu Lengaigne are funded by Institut de Recherche pour le Développement (IRD). Matthieu Lengaigne and Marina Lévy contributed to this paper while visiting the National Institute of Oceanography (NIO) in Goa, India. Marina Lévy’s visit was supported by TOSCA-CNES. Clement de Boyer Montegut is supported by the European Union via the seventh Framework Programme (INCO_LAB) GA295092 (INDO-MARECLIM). This has NIO contribution number.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2015

Authors and Affiliations

  • M. G. Keerthi
    • 1
  • M. Lengaigne
    • 2
    • 3
  • K. Drushka
    • 4
  • J. Vialard
    • 2
  • C. de Boyer Montegut
    • 5
  • S. Pous
    • 2
    • 6
  • M. Levy
    • 2
  • P. M. Muraleedharan
    • 1
  1. 1.National Institute of OceanographyCSIRDona PaulaIndia
  2. 2.LOCEAN, IPSLSorbonne Universités (UPMC, Univ Paris 06)-CNRS-IRD-MNHNParisFrance
  3. 3.Indo-French Cell for Water Sciences, IISc-NIO-IITM–IRD Joint International LaboratoryNIODona PaulaIndia
  4. 4.Applied Physics LaboratoryUniversity of WashingtonSeattleUSA
  5. 5.Laboratoire d’Océanographie SpatialeIFREMERBrestFrance
  6. 6.Department of OceanographyUniversity of Cape TownCape TownSouth Africa

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