The eddy kinetic energy budget in the Red Sea

Abstract

Abstract.The budget of eddy kinetic energy (EKE) in the Red Sea, including the sources, redistributions and sink, is examined using a high-resolution eddy-resolving ocean circulation model. A pronounced seasonally varying EKE is identified, with its maximum intensity occurring in winter, and the strongest EKE is captured mainly in the central and northern basins within the upper 200 m. Eddies acquire kinetic energy from conversion of eddy available potential energy (EPE), from transfer of mean kinetic energy (MKE), and from direct generation due to time-varying (turbulent) wind stress, the first of which contributes predominantly to the majority of the EKE. The EPEto-EKE conversion occurs almost in the entire basin, while the MKE-to-EKE transfer appears mainly along the shelf boundary of the basin (200 m isobath) where high horizontal shear interacts with topography. The EKE generated by the turbulent wind stress is relatively small and limited to the southern basin. All these processes are intensified during winter, when the rate of energy conversion is about four to five times larger than that in summer.The EKE is redistributed by the vertical and horizontal divergence of energy flux and the advection of the mean flow. As a main sink of EKE, dissipation processes is ubiquitously found in the basin. The seasonal variability of these energy conversion terms can explain the significant seasonality of eddy activities in the Red Sea.

Sensitivity Studies of the Red Sea Eddies Using Adjoint Method

“…The kinetic energy can be boosted when the baroclinic instability is triggered by a smaller Richardson number. This is consistent with the previous understandings of the general physical processes of eddies in the northern Red Sea (Zhan et al, ). Another difference between these CE experiments from the eddy dipole realization is that the sensitivity to along‐basin wind stress is larger than the cross‐basin wind stress.…”

“…Eddies in the Red Sea have been reported to be playing a crucial role in transporting energy, heat, and biogeochemical particles across the basin. The eddies make a remarkable contribution to the overturning circulation (Yao, Hoteit, Pratt, Bower, Köhl, et al, ; Yao, Hoteit, Pratt, Bower, Zhai, et al, ; Zhan et al, ), plankton blooms (Raitsos et al, ; Triantafyllou et al, ), species connectivity (Nanninga et al, ; Raitsos et al, ), brine, and discharge diffusion processes (Zhan et al, ), as well as other effects. In particular, a semipersistent cyclonic eddy (CE) in the northern Red Sea was reported to have uplifted colder water to the surface and created a substantial negative SST anomaly that was considered to favor the preconditioning of intermediate water formation (Papadopoulos et al, ).…”

“…Circulation in the Red Sea is highly variable and characterized by large surface temperature gradients (Bower & Farrar, 2015;Sofianos & Johns, 2007;Yao, Hoteit, Pratt, Bower, Zhai, et al, 2014), boundary currents (Bower & Farrar, 2015;Zhai et al, 2015;Zhan et al, 2015), and multiple recurrent and transient mesoscale and submesoscale eddies filling the basin (Chen et al, 2014;Papadopoulos et al, 2015;Zhai & Bower, 2013;Zhan et al, 2014Zhan et al, , 2016. Eddy activities have been captured by different types of observations, namely, remote sensing data from projects measuring Sea Level Anomalies (SLA; Bower & Farrar, 2015;Raitsos et al, 2017;Zhai & Bower, 2013;Zhan et al, 2014), Sea Surface Temperature (SST; Papadopoulos et al, 2015), chlorophyll-a (Raitsos et al, 2013), Synthetic Aperture Radar imagery (Karimova & Gade, 2014), and in situ observations (Sofianos & Johns, 2007).…”

Baroclinic Tides Simulation in the Red Sea: Comparison to Observations and Basic Characteristics

“…Among them, the narrow entrance at the Strait of BAM features higher values of KE than the other three areas. The maximum value of 7.86 kJ/m 2 also appears at the entrance of the BAM Strait; this value is larger than the maximum eddy KE value of 6 kJ/m 2 (Zhan et al, ). In the southern Red Sea, two long areas with high KE values along the edges of slopes, with higher values at the western side, indicate that baroclinic tides are mostly generated near the slopes and propagate toward the center of the trench.…”

“…Version c65x of the MITgcm was employed to simulate the baroclinic tides in the Red Sea. Considering the significant spatial and temporal variability, the tide simulation was conducted based on an ocean circulation model with realistic forcing that was successfully used to describe the overturning circulation (Yao, Hoteit, Pratt, Bower, Zhai, et al, ; Yao, Hoteit, Pratt, Bower, et al, ), seasonal variability (Zhan et al, ), and kinetic energy budget (Zhan et al, ) of mesoscale eddies and ensemble data assimilation (Toye et al, ) in the Red Sea.…”