Physico-chemical changes in continental shelf waters of the gulf of guinea and possible impacts on resource variability
Changes in the continental shelf ecosystem of Ghana were examined, based on sea surface and bottom temperature (SST, SBT), salinity and dissolved oxygen. The de-composed trend of temperatures exhibited a phase of cooling from the beginning of the series until 1976/77 and warming thereafter. The trend of salinity and dissolved oxygen showed different tendencies but in terms of timing, they were consistent with the pattern of change of temperature. These changes resulted in the division of the observational period into three blocks, namely the period before 1972, from 1972 to 1982 and the period after 1982. In the first block, sea surface temperature (both coastal and offshore) and bottom temperature declined, coastal salinity was low. The second block was colder, with less than average SST and SBT. The mixed layer was narrow with the thermocline remaining shallower than its long-term average position. Coastal and bottom salinity (measured at 100 m deep) were relatively high but the seasonal variation was minimal. This was a period of significant change in the physical components of the ecosystem of the Ghanaian shelf waters which to date has not been so clearly documented in the literature. In the final phase, temperatures were high, and salinity was low and erratic.
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