Formation and spreading of R ed S ea O utflow W ater in the R ed S ea

• Published in: Journal of geophysical research. Oceans Vol. 120; no. 9; pp. 6542 - 6563
• Main Authors: Zhai, Ping, Bower, Amy S., Smethie, William M., Pratt, Larry J.
• Format: Journal Article
• Language: English
• Published: 01-09-2015
• ISSN: 2169-9275; 2169-9291
• DOI: 10.1002/2015JC010751

Abstract
Hydrographic data, chlorofluorocarbon‐12 (CFC‐12) and sulfur hexafluoride (SF
6
) measurements collected in March 2010 and September–October 2011 in the Red Sea, as well as an idealized numerical experiment are used to study the formation and spreading of Red Sea Outflow Water (RSOW) in the Red Sea. Analysis of inert tracers, potential vorticity distributions, and model results confirm that RSOW is formed through mixed‐layer deepening caused by sea surface buoyancy loss in winter in the northern Red Sea and reveal more details on RSOW spreading rates, pathways, and vertical structure. The southward spreading of RSOW after its formation is identified as a layer with minimum potential vorticity and maximum CFC‐12 and SF
6
. Ventilation ages of seawater within the RSOW layer, calculated from the partial pressure of SF
6
(pSF
6
), range from 2 years in the northern Red Sea to 15 years at 17°N. The distribution of the tracer ages is in agreement with the model circulation field which shows a rapid transport of RSOW from its formation region to the southern Red Sea where there are longer circulation pathways and hence longer residence time due to basin wide eddies. The mean residence time of RSOW within the Red Sea estimated from the pSF
6
age is 4.7 years. This time scale is very close to the mean transit time (4.8 years) for particles from the RSOW formation region to reach the exit at the Strait of Bab el Mandeb in the numerical experiment.
Key Points:
RSOW is identified with low PV and high CFC‐12 and SF6
RSOW is formed through mixed‐layer deepening in winter in the northern Red Sea
Eddies can cause significant stirring and mixing