Process modeling studies of physical mechanisms of the formation of an anticyclonic eddy in the central Red Sea

Chen, Changsheng; Li, Ruixiang; Pratt, Lawrence J.; Limeburner, Richard; Beardsley, Robert C.; Bower, Amy S.; Jiang, Houshuo; Abualnaja, Yasser; Xu, Qinghai; Lin, Huichan; Liu, Xuehai; Lan, Jing; Kim, Tae Wan

doi:10.1002/2013jc009351

Cited by 38 publications

(50 citation statements)

References 39 publications

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“…However, the existence of the Tokar Gap wind jet observed in the MODIS imagery suggests that a simple model for the generation of an eddy dipole caused by surface wind stress [59] may not be appropriate in this situation. More complex models have been able to simulate long-lived anticyclonic eddies in other seasons [78], but the question of why this particular eddy appears to have a cold core in the SST data remains an area for future investigation.…”

Section: Discussionmentioning

confidence: 99%

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

El-Askary

Manikandan

et al. 2017

Remote Sensing

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An anomalously high chlorophyll-a (Chl-a) event (>2 mg/m 3 ) during June 2015 in the South Central Red Sea (17.5 • to 22 • N, 37 • to 42 • E) was observed using Moderate Resolution Imaging Spectroradiometer (MODIS) data from the Terra and Aqua satellite platforms. This differs from the low Chl-a values (<0.5 mg/m 3 ) usually encountered over the same region during summertime. To assess this anomaly and possible causes, we used a wide range of oceanographical and meteorological datasets, including Chl-a concentrations, sea surface temperature (SST), sea surface height (SSH), mixed layer depth (MLD), ocean current velocity and aerosol optical depth (AOD) obtained from different sensors and models. Findings confirmed this anomalous behavior in the spatial domain using Hovmöller data analysis techniques, while a time series analysis addressed monthly and daily variability. Our analysis suggests that a combination of factors controlling nutrient supply contributed to the anomalous phytoplankton growth. These factors include horizontal transfer of upwelling water through eddy circulation and possible mineral fertilization from atmospheric dust deposition. Coral reefs might have provided extra nutrient supply, yet this is out of the scope of our analysis. We thought that dust deposition from a coastal dust jet event in late June, coinciding with the phytoplankton blooms in the area under investigation, might have also contributed as shown by our AOD findings. However, a lag cross correlation showed a two-month lag between strong dust outbreak and the high Chl-a anomaly. The high Chl-a concentration at the edge of the eddy emphasizes the importance of horizontal advection in fertilizing oligotrophic (nutrient poor) Red Sea waters.

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Section: Discussionmentioning

confidence: 99%

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

El-Askary

Manikandan

et al. 2017

Remote Sensing

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“…Some previous observations in the Red Sea suggest that there is a cyclonic gyre in the northern Red Sea (Morcos and Soliman, 1974;Clifford et al, 1997;and Manasrah, 2004;Chen et al, 2014). The cyclonic gyre is also suggested in satellite SST images.…”

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confidence: 75%

“…For example, the cyclonic eddy in the northern Red Sea was reproduced by numerical simulations using the Miami Isopycnal Coordinate Ocean Model (MICOM), in an experiment forced only by surface buoyancy loss (Sofianos and Johns, 2003). Chen et al (2014) reproduced the 23°N anticyclonic eddy using the unstructured-grid, Finite-Volume Community Ocean Model 134 (FVCOM). They found that the eddy is formed by seasonally varying buoyancy forcing.…”

Section: Introductionmentioning

confidence: 99%

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Buoyancy-driven circulation in the Red Sea

Zhai¹

2014

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This thesis explores the buoyancy-driven circulation in the Red Sea, using a combination of observations, as well as numerical modeling and analytical method.The first part of the thesis investigates the formation mechanism and spreading of Red Sea Overflow Water (RSOW) in the Red Sea. The preconditions required for open-ocean convection, which is suggested to be the formation mechanism of RSOW, are examined. The RSOW is identified and tracked as a layer with minimum potential vorticity and maximum chlorofluorocarbon-12. The pathway of the RSOW is also explored using numerical simulation. If diffusivity is not considered, the production rate of the RSOW is estimated to be 0.63 Sv using Walin's method. By comparing this 0.63 Sv to the actual RSOW transport at the Strait of Bab el Mandeb, it is implied that the vertical diffusivity is about The second part of the thesis studies buoyancy-forced circulation in an idealized Red Sea. Buoyancy-loss driven circulation in marginal seas is usually dominated by cyclonic boundary currents on f-plane, as suggested by previous observations and numerical modeling. This thesis suggests that by including β-effect and buoyancy loss that increases linearly with latitude, the resultant mean Red Sea circulation consists of an anticyclonic gyre in the south and a cyclonic gyre in the north. In mid-basin, the northward surface flow crosses from the western boundary to the eastern boundary. The observational support is also reviewed. The mechanism that controls the crossover of boundary currents is further explored using an ad hoc analytical model based on PV dynamics. This ad hoc analytical model successfully predicts the crossover latitude of boundary currents. It suggests that the competition between advection of planetary vorticity and buoyancy-loss related term determines the crossover latitude.The third part of the thesis investigates three mechanisms that might account for eddy generation in the Red Sea, by conducting a series of numerical experiments. The three mechanisms are: i) baroclinic instability; ii) meridional structure of surface buoyancy losses; iii) cross-basin wind fields.

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“…Many inferences about the general circulation come from numerical simulations (e.g., Clifford et al 1997;Eshel and Naik 1997;Siddall et al 2002;Sofianos et al 2002;Sofianos and Johns 2003;Biton et al 2008Biton et al , 2010Chen et al 2014;Yao et al 2014a,b), most of which reproduce the northernmost gyre but which can differ in other aspects. There have been very few analytical models, laboratory experiments, or idealized numerical simulations apart from the celebrated Phillips (1966) model, but his restriction to a twodimensional overturning cell and his neglect of rotation are limiting.…”

Section: Introductionmentioning

confidence: 99%

On the Crossover of Boundary Currents in an Idealized Model of the Red Sea

Zhai

Pratt

Bower

2015

Journal of Physical Oceanography

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The west-to-east crossover of boundary currents has been seen in mean circulation schemes from several past models of the Red Sea. This study investigates the mechanisms that produce and control the crossover in an idealized, eddy-resolving numerical model of the Red Sea. The authors also review the observational evidence and derive an analytical estimate for the crossover latitude. The surface buoyancy loss increases northward in the idealized model, and the resultant mean circulation consists of an anticyclonic gyre in the south and a cyclonic gyre in the north. In the midbasin, the northward surface flow crosses from the western boundary to the eastern boundary. Numerical experiments with different parameters indicate that the crossover latitude of the boundary currents changes with f 0 , b, and the meridional gradient of surface buoyancy forcing. In the analytical estimate, which is based on quasigeostrophic, b-plane dynamics, the crossover is predicted to lie at the latitude where the net potential vorticity advection (including an eddy component) is zero. Various terms in the potential vorticity budget can be estimated using a buoyancy budget, a thermal wind balance, and a parameterization of baroclinic instability.

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Process modeling studies of physical mechanisms of the formation of an anticyclonic eddy in the central Red Sea

Cited by 38 publications

References 39 publications

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

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

Buoyancy-driven circulation in the Red Sea

On the Crossover of Boundary Currents in an Idealized Model of the Red Sea

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