CTD observations on the North Brazil shelf during a multidisciplinary Amazon Shelf Sediment Study, AMASSEDS, August 1989

Abstract

CTD and acoustic Doppler current profiler (ADCP) observations were made on the North Brazil shelf adjacent to the mouth of the Amazon River during R/V Iselin cruise I8909 August 3-14, 1989 as part of A Multidisciplinary Amazon Shelf SEDiment Study (AMASSEDS). These observations were obtained during a large-scale survey in support of geological and geochemical sampling, an anchored time series station consisting of 26 hourly CTD casts, and one transect which was repeated off the mouth of the Amazon River. The maximum sampling depth at each station was within two meters of the bottom. The primary objectives of the AMASSEDS hydrographic measurement program were to (a) observe and characterize the temperature, salinity, density, oxygen, fluorescence and light transmission fields and their spatial variability on the north Brazilian shelf directly influenced by the Amazon River discharge, (b) resolve the seaward extent and vertical structure of the surface plume of low salinity Amazon River water during different stages of river discharge, (c) describe the spatial structure of the turbidity and associated suspended sediment distributions across the shelf, (d) characterize the properties of the Amazon shelf water beneath the surface plume and their seasonal variability, and (e) describe the landward penetration of the North Brazil Current (NBC) with respect to water properties and shelf currents. This report represents a summary in graphic and tabular form of the hydrographic observations made during the first AMASSEDS cruise (I8909) on the R/V Iselin.