A simple box model of the Gulf of Aqaba, northern Red Sea, was used in order to study the effects of large scale processes in the Gulf and Red Sea (e.g. changes in thermohaline circulation or heat input from the Red Sea) as well as the influence of human activities (e.g. tourism, urbanization and mariculture) on the nutrient budget of the Gulf. The model employs available data from the literature together with General Circulation Model output data for monthly average temperature and salinity in the upper 200 m of the northern Red Sea, and monthly average meteorological data from the northern Gulf of Aqaba for heat flux and evaporation calculations. The model was shown to be most sensitive to changes in the thermohaline flux of Red Sea water through the Tiran Strait. Simulations of temperature and salinity best agreed with measurements when an annually varying thermohaline flux (0.045 Sv in January and 0.005 Sv in July) with decoupling of the thermohaline flow from the intermediate boxes during the summer (April-October) was employed. Additionally, periodic decrease of heat input from the Red Sea associated with regional weather patterns caused prolonged vertical mixing periods during the winters and shortening the residence time of phosphate in the Gulf. Hence, warming of Red Sea water would result in shorter periods of vertical mixing in the Gulf during the winter and accumulation of phosphate in the deep reservoir. The increase in deep reservoir phosphate can also be caused by an increase in the export flux of particulate organic matter to the deep reservoir. Hence, even a small increase in net primary production perhaps resulting from external nutrient input to the Gulf will result in nutrient accumulation in the deep reservoir. According to our model a return to pre-perturbation levels of phosphate in the Gulf would take on the order of 102 years.
Bibliographical noteFunding Information:
This work was supported by The Israel Science Foundation (grant no. 781/04). We would like to thank the national monitoring program for allowing us to access to their data base. We would also like to thank Jonathan Erez and Boaz Lazar for the fruitful discussion on the matters dealt within the paper. However, the content of this manuscript may not necessarily represent their personal opinions on the matters discussed. HG is the Incumbent of the Rowland and Sylvia Schaefer Career Development Chair.
- Active and passive tracer
- Gulf of Aqaba
- Red Sea
- Residence time
- Thermohaline circulation