Northern Arabian Sea Circulation – autonomous research (NASCar)

This initiative is fully subscribed.

The Northern Arabian Sea is dominated by both a strong western boundary current (speeds in excess of 2 ms-1), a large reservoir of heat in the mixed layer, and monsoon winds that have a dramatic impact on the circulation of the Arabian Sea and act to reverse the flow of some of the dominant circulation features. Frequent pirate activity occurs in the Arabian Sea. As a result, few in-situ oceanographic observations in the region have been made in the last decade, thus hampering the advancement of the oceanographic research in the region.

This lack of observations can be remedied through recent advances in technology that have allowed the production of low-cost, autonomous, expendable instruments that can be rapidly deployed in maritime and coastal waters by untrained personnel from vessels of opportunity. A distributed field of such ocean and atmospheric sensors can now operate on a sustained persistent basis for at least one year, in some cases longer, collecting data in previously inaccessible areas and reporting them reliably through various satellite networks systems.

This research program was motivated by the goal to understand the mixed layer and mesoscale dynamics in both basins relevant to understanding the Northern Indian Ocean monsoons. The unique air-sea interaction processes, fresh-water fluxes, boundary currents, and wind forcing have a strong impact on wind and buoyancy driven circulations, which in turn feedback on monsoon dynamics.

This research initiative will design an experiment in the Arabian Sea that will provide the data needed to develop a better understanding of the mixed layer physics and the western boundary current system and to constrain a hierarchy of numerical ocean models and coupled ocean-atmosphere models. The goal of the research initiative is to interweave the modeling and observational components of the program so that the modeling provides guidance about where and when to release instrumentation in order to sample the basin and achieve an improvement in the understanding of the physics. The goal of the observational program is to provide spatial-temporal sampling that resolves the two monsoonal seasons, concentrates on the ocean mixed-layer structure, and samples the structure of the western boundary current.

This research program is meant to complement the ongoing work in the Bay of Bengal ad to address the larger goal of understanding the ocean/atmosphere physics in the area needed to produce reliable and accurate ocean forecasts in a region of dominated by monsoonal dynamics.


ASIRI's overall objective is to:

  1. Understand and quantify dynamical processes and boundary transports that control fresh and salt water exchanges between the Northern Indian Ocean, the Bay of Bengal and the Southeast and Northern Arabian Seas; and
  2. Examine the responses to buoyancy and wind stress forcing using high-resolution air-sea coupled models of both the process and forecast-types.

NASCar’s research program needs to address these specific objectives:

  • Quantify currents, hydrography and mixed-layer depths in the Northern Arabian Sea (international waters) using autonomous instrumentation launched from the southern part of the basin.
  • Plan instrumentation releases, within the constraints of the program to resolve the two monsoonal seasons.
The overall goals of the NASCar DRI are to investigate the dynamics and space-time variability of the mixed layer and major boundary currents in the northern and western Arabian Sea and to improve the forecast of currents by using a novel approach, a combination of remote sensing, autonomous observations and a hierarchy of fine resolution numerical simulations and coupled ocean-atmosphere modeling.


  • There will be no UNOLS ship support for this program due to ongoing piracy and insurance issues
  • Logistics and facilitation has been arranged to deploy autonomous instrumentation from the Seychelles and from volunteer ships traversing the basin
  • Autonomous instrumentation will be supplied by the program- you can propose to be part of instrument programming and preparation or instrument related data use and analysis. The anticipated instrumentation include:
    • Gliders
    • Profiling floats
    • Drifters (simple or with T-chains, wave-measuring
    • Wave-gliders
  • All instrumentation will be programmed for one way missions – no recovery
  • International waters or obeying ARGO program type constraints

Partnerships: We are interested in pursuing closer scientific partnerships with local nations as interest allows and have established initial logistics and science agreements with Seychelles. We are interested in local capability-building as additional benefits of the program.

The DRI is expected to run for four years (FY15-FY18). In years one, the chosen investigators will focus on planning an field deployments using theoretical development, modeling and simulation; some initial deployments may occur as instrumentation becomes available and deployment methods become available.

We are looking for white papers addressing:

  • Modeling and lagrangian deployment strategies
  • Remote sensing
  • Data analysis as well as data assimilation
  • Instrumentation preparation and deployment

It is expected that some field effort will occur in FY15 and FY16 followed by two years of data analysis and synthesis of results. The overall effort will require integration of theory, observation and modeling to accelerate the discovery and understanding of this under-sampled basin.

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