The existing observations and model simulations indicate that mesoscale eddies
and the Eastern Boundary Current (EBC) have a significant role in the complex
circulation of the Red Sea. However, a full understanding of the processes that contribute
to the physics and biological responses of the central Red Sea (CRS) has been limited due
to the lack of sustained in-situ observations. In this dissertation study, in-situ observations
extending over a thirty-three month period from spring 2013 through winter 2015 include
an intensive ship-based and glider monitoring program to understand the key dynamic
features of the CRS circulation. Nine glider missions and five ship-based surveys provide
concrete resolution of both spatial and temporal variability in the CRS. The quasicontinuous
glider observations resolve the influence of distinct water masses with a
different origin that is present in the study area. Our results show that mesoscale eddies
and the an intrusion of Gulf of Aden water governs the physical and biochemical
characteristics of the CRS during the winter to summer transition period in 2013. During
this period, an anticyclonic eddy appears to redirect the northward flow along the eastern
boundary. Ship-based observations in fall 2013 indicate that the EBC can periodically
transport patches of less salty and warmer water containing higher chlorophyll
concentrations from south into the CRS. During spring 2014, ship observations show the
presence of a cyclonic/anticyclonic eddy pair. The cyclonic eddy contribute an upward
nutrient flux, resulting in an increase integrated chlorophyll concentration within the
eddy. Higher chlorophyll and CDOM concentrations and lower N:P ratios characterized
the inflow of lower salinity Gulf of Aden water from the south. To understand better how
the mesoscale eddy activity, stratification, and the EBC modulate the nutrient availability
and planktonic food web architecture in Red Sea two addition hydrographic surveys with
plankton sampling were conducted in fall 2014 and spring 2015. The seasonal availability
of Gulf of Aden water, stratification and eddies exerted a demonstrable effect on the
plankton community by modulating the availability and utilization of allochthonous vs.
autochthonous macronutrients by phytoplankton. Strong stratification, higher
temperatures and depletion of nutrients by phytoplankton, subjected the plankton
community to an overall nitrogen and phosphorus deficit in fall. To evaluate the role of
the winter mixing, mesoscale eddies, and EBC within CRS during the winter to spring
period, a sustained glider study (~91 days) was initiated from December 2014 to March
2015. Glider observations show the seasonal contrasts and transitions from strong
summer stratification to winter mixing, with a corresponding transition from a well
defined deep chlorophyll maximum to phytoplankton population intrusions of lower
salinity water from the Gulf of Aden contributed to both the physical and biochemical
variability within the region. Both GASW and GAIW can be entrained and diverted
across the basin by larger eddies. Eddies play a role in the mixing between warmer,
fresher water from the Gulf of Aden, and cooler, saltier water from the northern Red Sea.
| Identifer | oai:union.ndltd.org:kaust.edu.sa/oai:repository.kaust.edu.sa:10754/628313 |
| Date | 05 1900 |
| Creators | Zarokanellos, Nikolaos |
| Contributors | Jones, Burton, Biological and Environmental Science and Engineering (BESE) Division, Hoteit, Ibrahim, Voolstra, Christian R., Lee, Craig |
| Source Sets | King Abdullah University of Science and Technology |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Rights | 2019-08-28, At the time of archiving, the student author of this dissertation opted to temporarily restrict access to it. The full text of this dissertation became available to the public after the expiration of the embargo on 2019-08-28. |
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