Mesoscale eddies and boundary currents play a key role in the upper layer circulation of the Red Sea. This study assesses the physical and biochemical characteristics of an eastern boundary current (EBC) and recurrent eddies in the central Red Sea (CRS) using a combination of in situ and satellite observations. Hydrographic surveys in November 2013 (autumn) and in April 2014 (spring) in the CRS (22.15 − 24.1°N) included a total of 39 and 27 CTD stations, respectively. In addition, high-resolution hydrographic data were acquired in spring 2014 with a towed undulating vehicle (ScanFish). In situ measurements of salinity, temperature, chlorophyll fluorescence, colored dissolved organic matter (CDOM), and dissolved nitrate: phosphorous ratios reveal distinct water mass characteristics for the two periods. An EBC, observed in the upper 150 m of the water column during autumn, transported low-salinity and warm water from the south toward the CRS. Patches of the low-salinity water of southern origin tended to contain relatively high concentrations of chlorophyll and CDOM. The prominent dynamic feature observed in spring was a cyclonic/anticyclonic eddy pair. The cyclonic eddy was responsible for an upward nutrient flux into the euphotic zone. Higher chlorophyll and CDOM concentrations, and concomitant lower nitrate:phosphorous ratios indicate the influence of the EBC in the CRS at the end of the stratified summer period.
KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: Research reported in this publication was supported by the King Abdullah University of Science and Technology (KAUST). Hydrographic data obtained from both cruises can be obtained from Burton H. Jones (KAUST) and Nikolaos D. Zarokanellos (KAUST). The authors gratefully acknowledge the Core Marine Operation Research Lab (CMOR) for their support during the cruises. Special thanks go to Ioannis Georgakakis, Y. V. B. Sarma and Mohammedali Nellayaputhenpeedika for their technical support during the cruises. Also, we thank the captain and crew of R/V Thuwal for their valued help during the Eddy Shelf Expedition. The SLA was obtained from AVISO and the ocean color products were produced by NASA Ocean Color Group; satellite data are available online through the official websites documented in section 2. We thank Ian Walsh and an anonymous reviewer for their valuable comments and suggestions.