Document Type


Publication Date


Digital Object Identifier (DOI)<0584:PTIAIO>2.0.CO;2


Trajectory experiments in a thermocline layer of an Indian Ocean model are used to investigate the role of different meridional transport mechanisms and quantify spreading pathways and rates under different forcing. Particles are introduced along two boundaries: the south Indian Ocean at 30 degrees S and the Indonesian Throughflow. Particles are advected horizontally within the layer by archived model velocity fields (1/3 degrees X 1/3 degrees resolution) for a period of 50 years. The velocity fields are the result of forcing the model by monthly mean climatology (case A). The distribution of particles within the Tropics suggests efficient ater mass blending; model results show a mixture of three parts South Indian Central Water to one part Indonesian Throughflow. In agreement with chlorofluorocarbon (CFC) observations. transport of thermocline waters along the western boundary into the northern Indian Ocean occurs on timescales of less than two decades. Additional Lagrangian experiments carried out with the seasonality removed from the velocity fields directly (taking the mean in case B) and from the forcing (case C) allow the role of horizontal eddy transport to be evaluated. Significant northward transport of southern subtropical gyre waters along the western boundary does not occur unless there is eddy transport, even though the mean flow appears to dominate the cross-equatorial transport in the immediate vicinity of the equator. Particles reach northward of 10 degrees N on shorter timescales (yr) in case A: compared with case C (>20 yr). Both the mean and seasonal forcing components are important for the meridional flux of particles. The results suggest that to adequately simulate meridional transport of mass and water mass properties in the Indian Ocean, models should include the full annual cycle. In a new methodology, CFC-II concentrations along trajectories are calculated using observed CFC-11 concentrations for boundary conditions. Additional CFC observations allow model-data comparisons to be made in the interior of the domain. The method may be useful in other studies of transport rates and processes where both computing power and good quality high-resolution observations are available.

Citation / Publisher Attribution

Journal of Physical Oceanography, v. 29, issue 4, p. 584-598

© Copyright 1999 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act or that satisfies the conditions specified in Section 108 of the U.S. Copyright Act (17 USC §108) does not require the AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a website or in a searchable database, or other uses of this material, except as exempted by the above statement, requires written permission or a license from the AMS. All AMS journals and monograph publications are registered with the Copyright Clearance Center ( Questions about permission to use materials for which AMS holds the copyright can also be directed to Additional details are provided in the AMS Copyright Policy statement, available on the AMS website (