scholarly journals Mesoscale eddies and submesoscale structures of Persian Gulf Water off the Omani coast in spring 2011

Ocean Science ◽  
2016 ◽  
Vol 12 (3) ◽  
pp. 687-701 ◽  
Author(s):  
Pierre L'Hégaret ◽  
Xavier Carton ◽  
Stephanie Louazel ◽  
Guillaume Boutin
Keyword(s):  
Persian Gulf ◽  
Arabian Sea ◽  
Cold Water ◽  
Mesoscale Eddies ◽  
High Salinity Water ◽  
Strait Of Hormuz ◽  
Persian Gulf Water ◽  
Salinity Water ◽  
The Persian Gulf ◽  
Sea Of Oman

Abstract. The Persian Gulf produces high-salinity water (Persian Gulf Water, PGW hereafter), which flows into the Sea of Oman via the Strait of Hormuz. Beyond the Strait of Hormuz, the PGW cascades down the continental slope and spreads in the Sea of Oman under the influence of the energetic mesoscale eddies. The PGW outflow has different thermohaline characteristics and pathways, depending on the season. In spring 2011, the Phys-Indien experiment was carried out in the Arabian Sea and in the Sea of Oman. The Phys-Indien 2011 measurements, as well as satellite observations, are used here to characterize the circulation induced by the eddy field and its impact on the PGW pathway and evolution. During the spring intermonsoon, an anticyclonic eddy is often observed at the mouth of the Sea of Oman. It creates a front between the eastern and western parts of the basin. This structure was observed in 2011 during the Phys-Indien experiment. Two energetic eddies were also present along the southern Omani coast in the Arabian Sea. At their peripheries, ribbons of freshwater and cold water were found due to the stirring created by the eddies. The PGW characteristics are strongly influenced by these eddies. In the western Sea of Oman, in 2011, the PGW was fragmented into filaments and submesoscale eddies. It also recirculated locally, thus creating salty layers with different densities. In the Arabian Sea, a highly saline submesoscale lens was recorded offshore. Its characteristics are analyzed here and possible origins are proposed. The recurrence of such lenses in the Arabian Sea is also briefly examined.

scholarly journals Mesoscale eddies and submesoscale structures of Persian Gulf Water off the Omani coast in Spring 2011

2015 ◽  
Vol 12 (6) ◽  
pp. 2743-2782
Author(s):  
P. L'Hégaret ◽  
X. Carton ◽  
S. Louazel ◽  
G. Boutin
Keyword(s):  
Persian Gulf ◽  
Arabian Sea ◽  
High Salinity ◽  
Cold Water ◽  
Mesoscale Eddies ◽  
High Salinity Water ◽  
Persian Gulf Water ◽  
Salinity Water ◽  
The Persian Gulf ◽  
Sea Of Oman

Abstract. The Persian Gulf produces a high salinity water (Persian Gulf Water, PGW hereafter) flowing into the Sea of Oman, in the northwestern Indian Ocean. Past the Strait of Hormuz, the PGW cascades down the continental slope and spreads in the Sea of Oman under the influence of the energetic mesoscale eddies with different thermohaline signatures and pathways depending of the season. In spring 2011, the Phys-Indien experiment was carried out in the Arabian Sea an in the Sea of Oman. This study uses the results from the measurements to characterize the water masses, their thermohaline and dynamical signatures. During the spring intermonsoon, an anticyclonic eddy is often observed at the mouth of the Sea of Oman. This structure was present in 2011 and created a front between the eastern and western part of the basin. As well two energetic gyres were present along the Omani coast in the Arabian Sea. At their peripheries, injections of fresh and cold water are found in relation with the stirring of the eddies. The PGW observed below or between these eddies have a different dilution depending of the position and formation periods of the gyres. Furthermore, in the western Sea of Oman, the PGW is fragmented in filaments and submesoscale eddies. As well, recirculation of the PGW is observed, thus having the presence of salty nearby patches with two densities. Offshore, in the Arabian Sea, a submesoscale lens was recorded. The different mechanisms leading to its formation and presence are assessed here.

scholarly journals Mesoscale variability in the Arabian Sea from HYCOM model results and observations: impact on the Persian Gulf Water path

Ocean Science ◽  
2015 ◽  
Vol 11 (5) ◽  
pp. 667-693 ◽  
Author(s):  
P. L'Hégaret ◽  
R. Duarte ◽  
X. Carton ◽  
C. Vic ◽  
D. Ciani ◽  
...  
Keyword(s):  
Persian Gulf ◽  
Arabian Sea ◽  
Meteorological Data ◽  
Mesoscale Eddies ◽  
Ocean Model ◽  
Water Masses ◽  
Dimensional Structure ◽  
Persian Gulf Water ◽  
The Persian Gulf ◽  
Sea Of Oman

Abstract. The Arabian Sea and Sea of Oman circulation and water masses, subject to monsoon forcing, reveal a strong seasonal variability and intense mesoscale features. We describe and analyze this variability and these features, using both meteorological data (from ECMWF reanalyses), in situ observations (from the ARGO float program and the GDEM – Generalized Digital Environmental mode – climatology), satellite altimetry (from AVISO) and a regional simulation with a primitive equation model (HYCOM – the Hybrid Coordinate Ocean Model). The model and observations display comparable variability, and the model is then used to analyze the three-dimensional structure of eddies and water masses with higher temporal and spatial resolutions than the available observations. The mesoscale features are highly seasonal, with the formation of coastal currents, destabilizing into eddies, or the radiation of Rossby waves from the Indian coast. The mesoscale eddies have a deep dynamical influence and strongly drive the water masses at depth. In particular, in the Sea of Oman, the Persian Gulf Water presents several offshore ejection sites and a complex recirculation, depending on the mesoscale eddies. The associated mechanisms range from coastal ejection via dipoles, alongshore pulses due to a cyclonic eddy, to the formation of lee eddies downstream of Ra's Al Hamra. This water mass is also captured inside the eddies via several mechanisms, keeping high thermohaline characteristics in the Arabian Sea. The variations of the outflow characteristics near the Strait of Hormuz are compared with variations downstream.

scholarly journals Mesoscale variability in the Arabian Sea from HYCOM model results and observations: impact on the Persian Gulf Water path

2015 ◽  
Vol 12 (2) ◽  
pp. 493-550 ◽  
Author(s):  
P. L'Hégaret ◽  
R. Duarte ◽  
X. Carton ◽  
C. Vic ◽  
D. Ciani ◽  
...  
Keyword(s):  
Persian Gulf ◽  
Seasonal Variability ◽  
Arabian Sea ◽  
Meteorological Data ◽  
Mesoscale Eddies ◽  
Water Masses ◽  
Dimensional Structure ◽  
Persian Gulf Water ◽  
The Persian Gulf ◽  
Sea Of Oman

Abstract. The Arabian Sea and Sea of Oman circulation and water masses, subject to the monsoon forcing, reveal a strong seasonal variability and intense mesoscale features. We describe and analyse this variability and these features, using both meteorological data (from ECMWF reanalyses), in-situ observations (from the ARGO float program and the GDEM climatology), satellite altimetry (from AVISO) and a regional simulation with a primitive equation model (HYCOM). The EOFs of the seasonal variability of the water masses quantify their main changes in thermohaline characteristics and in position. The model and observations display comparable variability, and the model is then used to analyse the three-dimensional structure of eddies and water masses with a higher resolution. The mesoscale eddies have a deep dynamical influence and strongly drive the water masses at depth. In particular, in the Sea of Oman, the Persian Gulf Water presents several offshore ejection sites and a complex recirculation, depending on the mesoscale eddies. This water mass is also captured inside the eddies via several mechanisms, keeping high thermohaline characteristics in the Arabian Sea. These characteristics are validated on the GOGP99 cruise data.

scholarly journals The life cycle of submesoscale eddies generated by topographic interactions

2019 ◽  
Author(s):  
Mathieu Morvan ◽  
Pierre L'Hégaret ◽  
Xavier Carton ◽  
Jonathan Gula ◽  
Clément Vic ◽  
...  
Keyword(s):  
Life Cycle ◽  
Red Sea ◽  
Persian Gulf ◽  
Sea Water ◽  
Mesoscale Eddies ◽  
Shear Instability ◽  
Gulf Of Oman ◽  
Coherent Vortices ◽  
Persian Gulf Water ◽  
The Persian Gulf

Abstract. The Persian Gulf Water and Red Sea Water are salty and dense waters recirculating at subsurface in the Gulf of Oman and the Gulf of Aden respectively, under the influence of mesoscale eddies which dominate the surface flow in both semi-enclosed basins. In situ measurements combined with altimetry indicate that the Persian Gulf Water is driven by mesoscale eddies in the form of filaments and submesoscale structures. In this paper, we study the formation and the life cycle of intense submesoscale vortices and their impact on the spread of Persian Gulf Water and Red Sea Water. We use a three-dimensional hydrostatic model with submesoscale-resolving resolution to study the evolution of submesoscale vortices. Our configuration is an idealized version of the Gulf of Oman and Aden: a zonal row of mesoscale vortices interacting with north and south topographic slopes. Intense submesoscale vortices are generated in the simulations along the continental slopes due to two different mechanisms. The first mechanism is due to frictional generation of vorticity in the bottom boundary layer, which detaches from the topography, forms an unstable vorticity filament, and undergoes horizontal shear instability that leads to the formation of submesoscale coherent vortices. The second mechanism is inviscid and implies arrested topographic Rossby waves breaking and forming submesoscale coherent vortices where a mesoscale anticyclone interacts with the topographic slope. Submesoscale vortices subsequently drift away, merge and form larger vortices. They can also pair with opposite signed vortices and travel across the domain. They can weaken or disappear via several mechanisms, in particular fusion into the larger eddies or erosion on the topography. Particle patches are advected and sheared by vortices and are entrained into filaments. Their size first grows as the square root of time, a signature of the merging processes, then it increases linearly with time, corresponding to their ballistic advection by submesoscale eddies. On the contrary, witout intense submesoscale eddies, particles are mainly advected by mesoscale eddies; this implies a weaker dispersion of particles than in the previous case. This shows the important role of submesoscale eddies in spreading Persian Gulf Water and Red Sea Water.

A Modeling Study of Circulation and Eddies in the Persian Gulf

2010 ◽  
Vol 40 (9) ◽  
pp. 2122-2134 ◽  
Author(s):  
Prasad G. Thoppil ◽  
Patrick J. Hogan
Keyword(s):  
Persian Gulf ◽  
Spatial Scales ◽  
Baroclinic Instability ◽  
Mesoscale Eddies ◽  
Ocean Model ◽  
Coastal Current ◽  
Basin Scale ◽  
Strait Of Hormuz ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
The Persian Gulf

Abstract The circulation and mesoscale eddies in the Persian Gulf are investigated using results from a high-resolution (∼1 km) Hybrid Coordinate Ocean Model (HYCOM). The circulation in the Persian Gulf is composed of two spatial scales: basin scale and mesoscale. The progression of a cyclonic circulation cell dominates the basin-scale circulation in the eastern half of the gulf (52°–55°E) during March–July. This is primarily the consequence of density-driven outflow–inflow through the Strait of Hormuz and strong stratification. A northwestward-flowing Iranian Coastal Current (ICC; 30–40 cm s−1) between the Strait of Hormuz and north of Qatar (∼52°E) forms the northern flank of the cell. Between July and August the ICC becomes unstable because of the baroclinic instability mechanism by releasing the potential energy stored in the cross-shelf density gradient. As a result, the meanders in the ICC evolve into a series of mesoscale eddies, which is denoted as the Iranian coastal eddies (ICE). The ICE have a diameter of about 115–130 km and extend vertically over most of the water column. Three cyclonic eddies produced by the model during August–September 2005 compared quite well with the Moderate Resolution Imaging Spectroradiometer (MODIS) SST and chlorophyll-a observations. The remnants of ICE are seen until November, after which they dissipate as the winter cooling causes the thermocline to collapse.

scholarly journals Seasonal spreading of the Persian Gulf Water mass in the Arabian Sea

2001 ◽  
Vol 106 (C8) ◽  
pp. 17059-17071 ◽  
Author(s):  
T. G. Prasad ◽  
M. Ikeda ◽  
S. Prasanna Kumar
Keyword(s):  
Persian Gulf ◽  
Arabian Sea ◽  
Water Mass ◽  
Persian Gulf Water ◽  
The Persian Gulf

scholarly journals The structure of the Persian Gulf outflow subjected to density variations

2008 ◽  
Vol 5 (2) ◽  
pp. 135-161 ◽  
Author(s):  
A. A. Bidokhti ◽  
M. Ezam
Keyword(s):  
Mass Transport ◽  
Persian Gulf ◽  
Anthropogenic Factors ◽  
Oman Sea ◽  
The Earth ◽  
Salinity Increase ◽  
Persian Gulf Water ◽  
Oceanographic Data ◽  
The Persian Gulf ◽  
Simple Dynamical Model

Abstract. Oceanographic data and a dynamic model are used to consider the structure of Persian Gulf outflow. This outflow influences the physical properties of Oman seawater which appear in the CTD profiles of the Oman Sea. The observations show that thickness of the outflow, which is banked against the Oman coasts due to the earth rotation, is about 200 m with tongues extending east and north that may be due to the internal waves. A simple dynamical model of the outflow based on potential vorticity conservation is used to find the horizontal extension of the outflow from the coast. Typical mass transport estimate by the outflow is about 0.4 Sv, which is larger than those reported by others. This may be due to the fact the model is inviscid but the outflow is influenced by the bottom friction. Variability of the outflow structure may reflect the changing ecosystem of the Persian Gulf. Any change of the outflow source, the Persian Gulf Water (PGW), say salinity increase due to excessive evaporation (climate factor) or desalination (anthropogenic factors) of the PGW may change the outflow structure and the product waters in the Oman Sea. Hence, one can test different scenarios of changing the outflow source, the Persian Gulf Water (PGW), say by salinity increase due to excessive evaporation or desalination (ecosystem factors) of the PGW to estimate changes in the outflow structure and the product waters in the Oman Sea. The results of the model show that these can increase the outflow width and mass transport substantially.

scholarly journals Estimation of the Heat and Water Budgets of the Persian (Arabian) Gulf Using a Regional Climate Model*,+

2015 ◽  
Vol 28 (13) ◽  
pp. 5041-5062 ◽  
Author(s):  
Pengfei Xue ◽  
Elfatih A. B. Eltahir
Keyword(s):  
Heat Flux ◽  
Regional Climate Model ◽  
Persian Gulf ◽  
Arabian Sea ◽  
Climate Model ◽  
Regional Climate ◽  
Surface Heat ◽  
Surface Fluxes ◽  
Water Budgets ◽  
The Persian Gulf

Abstract Because of the scarcity of observational data, existing estimates of the heat and water budgets of the Persian Gulf are rather uncertain. This uncertainty leaves open the fundamental question of whether this water body is a net heat source or a net heat sink to the atmosphere. Previous regional modeling studies either used specified surface fluxes to simulate the hydrodynamics of the Gulf or prescribed SST in simulating the regional atmospheric climate; neither of these two approaches is suitable for addressing the above question or for projecting the future climate in this region. For the first time, a high-resolution, two-way, coupled Gulf–atmosphere regional model (GARM) is developed, forced by solar radiation and constrained by observed lateral boundary conditions, suited for the study of current and future climates of the Persian Gulf. Here, this study demonstrates the unique capability of this model in consistently predicting surface heat and water fluxes and lateral heat and water exchanges with the Arabian Sea, as well as the variability of water temperature and water mass. Although these variables are strongly coupled, only SST has been directly and sufficiently observed. The coupled model succeeds in simulating the water and heat budgets of the Persian Gulf without any artificial flux adjustment, as demonstrated in the close agreement of model simulation with satellite and in situ observations. The coupled regional climate model simulates a net surface heat flux of +3 W m−2, suggesting a small net heat flux from the atmosphere into the Persian Gulf. The annual evaporation from the Persian Gulf is 1.84 m yr−1, and the annual influx and outflux of water through the Strait of Hormuz between the Persian Gulf and Arabian Sea are equivalent to Persian Gulf–averaged precipitation and evaporation rates of 33.7 and 32.1 m yr−1, with a net influx of water equivalent to a Persian Gulf–averaged precipitation rate of 1.6 m yr−1. The average depth of the Persian Gulf water is ~38 m. Hence, it suggests that the mean residency time scale for the entire Persian Gulf is ~14 months.

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