Eddies in the Red Sea: A statistical and dynamical study

Abstract

Sea level anomaly (SLA) data spanning 1992-2012 were analyzed to study the statistical properties of eddies in the Red Sea. An algorithm that identifies winding angles was employed to detect 4998 eddies propagating along 938 unique eddy tracks. Statistics suggest that eddies are generated across the entire Red Sea but that they are prevalent in certain regions. A high number of eddies is found in the central basin between 18 N and 24 N. More than 87% of the detected eddies have a radius ranging from 50 to 135 km. Both the intensity and relative vorticity scale of these eddies decrease as the eddy radii increase. The averaged eddy lifespan is approximately 6 weeks. AEs and cyclonic eddies (CEs) have different deformation features, and those with stronger intensities are less deformed and more circular. Analysis of long-lived eddies suggests that they are likely to appear in the central basin with AEs tending to move northward. In addition, their eddy kinetic energy (EKE) increases gradually throughout their lifespans. The annual cycles of CEs and AEs differ, although both exhibit significant seasonal cycles of intensity with the winter and summer peaks appearing in February and August, respectively. The seasonal cycle of EKE is negatively correlated with stratification but positively correlated with vertical shear of horizontal velocity and eddy growth rate, suggesting that the generation of baroclinic instability is responsible for the activities of eddies in the Red Sea.

Carbon and nitrogen stable isotope ratios of pelagic zooplankton elucidate ecohydrographic features in the oligotrophic Red Sea

“…Moreover, this study provides an explanation for an upwelling mechanism near the Atlantis II station, for which additional multiple and complementary evidence exists, including nutrient data, POM, phytoplankton count and modeled zooplankton food source data (see discussion below). In fact, modeling studies already indicate that the general Red Sea upper water flow is affected by a temporally and spatially variable and complex array of eddy systems (Zhan et al, 2014). We suggest, therefore, that eddies have the potential to interact with the general thermohaline circulation of the Red Sea, but with variable lifespan and positioning ( Fig.…”

Synergistic Use of Remote Sensing and Modeling to Assess an Anomalously High Chlorophyll-a Event during Summer 2015 in the South Central Red Sea

“…There is also evidence of multiple eddies, especially along the western part of the basin. Such eddies are common in the area [3], and have been implicated in increases in phytoplankton by a number of authors [2,[16][17][18][19][20]22].…”

“…However, it is likely that the 0.33 • resolution of the OSCAR data is insufficient to resolve the pair of cyclonic eddies apparent in the higher resolution SSH data. The formation of an eddy dipole in the western Red Sea near 19 • N with a cyclonic eddy to the north and an anticyclonic eddy to the south has been attributed to the influence of a wind jet associated with the Tokar Gap [59], which is active throughout the boreal summer [3,[63][64][65] and a large source of atmospheric dust [66]. is associated with locally cooler SSTs, even though the SSH is elevated.…”

“…The basin extends to about 30 • N in the Gulf of Suez and the Gulf of Aqaba (Eilat) and terminates to the south at the straits of Bab al Mandeb at approximately 12.5 • N. The length of the Red Sea is roughly 2250 km, with a maximum width of 355 km and a maximum depth of 3040 m; although the average depth is 490 m [2,3]. The Red Sea has no river inflow or stream sources and has a high evaporation rate at more than 210 cm/yr [4] and a precipitation rate of less than 100 mm/yr [5,6], resulting in the highest salinity of any major tropical oceanic basin [4].…”

Quantifying and Interpreting Striations in a Subtropical Gyre: A Spectral Perspective

“…The dynamic reasons for the formation of the nondispersive line in the spectra remain unclear. Besides the Okubo-Weiss parameter, other methods to split eddies into vortices and background motions exist, such as the winding angle method and the wavelet transform method (e.g., Ari Sadarjoen and Post 2000;Ruppert-Felsot et al 2005;Zhan et al 2014). Descriptions and theories about the respective contribution of vortices and the background field to the nondispersive line and to striation energy remain to be done.…”