Summary of Abstract Submission

Abstract Submission No. IO50-04-0029PresentationOral

THE INTERPLAY OF THE EAST AFRICAN COASTAL CURRENT AND TIDAL DYNAMICS ON THE CURRENTS ON THE EAST COAST OF ZANZIBAR ISDLANDS, TANZANIA.

Prof Ntahondi NYANDWI*1, Mr D. S. Mukaka1

1 University of Dar es Salaam, Institute of Marine Sciences, Tanzania

ABSTRACT :

The tidal dynamics and effects of the EACC off the coast of Zanzibar islands have recently been explored. Time series of currents and tides were subjected to harmonic analysis of least squares fit coupled with hydrodynamic modelling (ROMS). The findings provide tidal conditions and circulation off Zanzibar Island which can be used in many practical applications and fill the existing scientific knowledge gap on local ocean circulation within the East African Coastal Current system. The most dominant tidal wave in the region M2, N2, K1 and O1 with the exception of S2, induce very minimal tidal currents in the study area. The eddy activity and non tidal streams activity are greater than tidal currents activity. Characteristic flow parameters are: Velocity max (mm/s): West 281, East 174, South 474, North 328, down 172, and up 243. Mean: West 47.5, South 59.4, down 19.5. Water speed max 521, mean 126. Flood 204.2o, ebb 24.2o. The tide is semidiurnal F (0.16) and Macrotidal regime of tidal range 4.1m. The foremost tides (mm) are M2 (1057.08), S2 (684.04), N2 (238.74), K1 (157.6), O1 (111.5), tidal currents (mm/s) are MM (59.34), S2 (48.76), MSF (40.54), SN4 (24.2), MU2 (23.6), M4 (21.13), and K1 (19.57), their inclination follow the water flow N-S along eddy passage. The incoming and outgoing tidal waves form an eddy that spiral counter clockwise. Both the offshore incoming and outgoing tidal waves show northward flow that signifies the control of the northward flowing EACC.