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First observational evidence of a North Madagascar Undercurrent
Ponsoni, L.; Aguiar-Gonzáles, B.; Nauw, J.; Ridderinkhof, H.; Maas, L.R.M. (2015). First observational evidence of a North Madagascar Undercurrent. Dyn. Atmos. Oceans 72: 12-20.
In: Dynamics of Atmospheres and Oceans. Elsevier: Amsterdam; New York; Oxford; Tokyo. ISSN 0377-0265; e-ISSN 1872-6879, more
Peer reviewed article  

Available in  Authors 

Author keywords
    North Madagascar Undercurrent; North Madagascar Current; Indian Ocean; Coastal downwelling; South Indian Central Water

Authors  Top 
  • Ponsoni, L., more
  • Aguiar-Gonzáles, B., more
  • Nauw, J., more
  • Ridderinkhof, H., more
  • Maas, L.R.M., more

    In situ observations reveal a southeastward-directed North Madagascar Undercurrent (NMUC) below and opposite to the equatorward-directed North Madagascar Current (NMC) off Cape Amber, at the northern tip of Madagascar. Results show an undercurrent hugging the continental slope with its core at 460 m depth and velocities over 0.7 m s-1. Its volume transport is estimated to be 3.1–3.8 Sv, depending on the velocity extrapolation methods used to fill in the data gaps near the slope (no-slip and full-slip, respectively). The thermohaline characteristics show a saltier and warmer NMUC, compared to the surrounding offshore waters, transporting mainly South Indian Central Water. Also, strong horizontal gradients of density are found in the NMUC domain. An inshore cell of coastal downwelling due to Ekman Transport toward the coast is identified, which can explain, at least in part, the strong baroclinic pressure gradients as well as the NMUC development and possible persistence.

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