Analysis of abyssal currents measured at 7 levels viz., 4, 8, IS, 30, 50, 100 and 500 mab during October 1996 -April 1997 at 10°01 " S,76°E in the Benthic Disturbance Experiment Site (BDES) in the Central Indian Ocean Basin is presented. Monthly mean currents showed a general SSE flow and suggested seasonal variability in the flow pattern with a reversal in January. The variation of 6 month-mean current speed indicated near-bottom intensification of the flow at 50 mab and presence of Bottom Ekman Layer (BEL) below 50 mab. Above BEL the total KE at each depth was dominated by eddy KE resulted from synoptic scale (1215 day period) motions. It is found that BDES was highly energetic (2-3 folds) compared to nearby location ~100 km to the west of BDES.


Dispersion characteristics of the sediment plume that is generated on account of any sediment disturbance activity (mining) largely depend upon the current velocities and their vertical structures in the benthic layer. Therefore, information on the variability of the ocean currents in the benthic layer is very much essential. Keeping this in mind, a current meter mooring with current meters at close depth intervals covering the benthic layer was planned at the proposed Benthic Disturbance Experiment Site (BDES) in the Central Indian Ocean Basin (CIOB). The observational programme was conducted as a part of baseline studies for the Environmental Impact Assessment" due to the envisaged manganese nodule mining activity in future. A short-mooring consisting of eight recording current meters (RCMs) at close intervals in the lower 500 m water column above the sea bed of the BDES was deployed at 10° 01" S, 75° 59.8" E (location I, assigned station No. MS-5) during October1996 - first week of May 1997.

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