CTD observations on the North Brazil shelf during a multidisciplinary Amazon Shelf Sediment Study, AMASSEDS, May-June 1990

Abstract

Hydrographic (CTD) and acoustic Doppler current profiler (ADCP) observations were made on the North Brazil shelf adjacent to the mouth of the Amazon River durng R/V ¡"elin cruise 19113 November 5-25, 1991 as par of A Multidisciplinar Amazon Shelf SEDiment Study (AMASSEDS). These observtions were obtaied durng a large-scale suey on Leg 3 in support of geological and geoemica sapling, and durng a frontal zone surey on Leg 4 consisting of 14 and 26 hourly CTD casts at anchored stations. The maximum sampling depth at eac station was within two meters of the bottom. The primar objectives of the AMASSEDS hydrograpmc measurement program were (a) to observe and characterize the temperature, salnity, density, oxygen, fluores- cence and light transmission fields and their spatial varabilty on the north Brazilian shelf diectly inuenced by the Amazon River discharge, (b) to resolve the seaward extent and vertical structure of the sunace plume of low salinity Amazon River water durng dierent stages of river' discharge, (c) to describe the spatial structure of the turbidity and associ- ated suspended sediment distributions across the shelf, (d) to characterize the properties of the Amazon shelf water beneath the surace plume and their seasonal varabilty, and (e) to describe the landward penetration of the North Brazil Curent with respect to water properties and shelf curents. This report represents a sumary in grapmc and tabular form of the hydrographic observations made durg the fourh AMASSEDS cruise (19113) on the R/V belin.