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

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.

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

Ocean Science ◽

10.5194/os-12-687-2016 ◽

2016 ◽

Vol 12 (3) ◽

pp. 687-701 ◽

Cited By ~ 18

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.

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

Ocean Science ◽

10.5194/os-11-667-2015 ◽

2015 ◽

Vol 11 (5) ◽

pp. 667-693 ◽

Cited By ~ 21

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.

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

Ocean Science Discussions ◽

10.5194/osd-12-493-2015 ◽

2015 ◽

Vol 12 (2) ◽

pp. 493-550 ◽

Cited By ~ 1

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.

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The life cycle of submesoscale eddies generated by topographic interactions

10.5194/os-2019-3 ◽

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.

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A Prolonged High-Salinity Event in the Northern Arabian Sea during 2014–17

Journal of Physical Oceanography ◽

10.1175/jpo-d-19-0220.1 ◽

2020 ◽

Vol 50 (4) ◽

pp. 849-865 ◽

Cited By ~ 1

Author(s):

Yuhong Zhang ◽

Yan Du ◽

W. N. D. S Jayarathna ◽

Qiwei Sun ◽

Ying Zhang ◽

...

Keyword(s):

Arabian Sea ◽

High Salinity ◽

Southwest Monsoon ◽

Early Summer ◽

Current Data ◽

Gulf Of Oman ◽

High Salinity Water ◽

Northern Arabian Sea ◽

Salinity Increase ◽

Salinity Water

AbstractA prolonged high-salinity event in the northern Arabian Sea, to the east of the Gulf of Oman, during 2014–17 was identified based on Argo datasets. The prolonged event was manifested as enhanced spreading of the surface Arabian Sea high-salinity water and the intermediate Persian Gulf water. We used satellite altimetric data and geostrophic current data to understand the oceanic processes and the salt budget associated with the high-salinity event. The results indicated that the strengthened high-salinity advection from the Gulf of Oman was one of the main causes of the salinity increase in the northern Arabian Sea. The changes of the seasonally dependent eddies near the mouth of the Gulf of Oman dominated the strengthened high-salinity advection during the event as compared with the previous 4-yr period: the westward shifted cyclonic eddy during early winter stretched to the remote western Gulf of Oman, which carried the higher-salinity water to the northern Arabian Sea along the south coast of the Gulf. An anomalous eddy dipole during early summer intensified the eastward Ras Al Hadd Jet and its high-salinity advection into the northern Arabian Sea. In addition, the weakened low-salinity advection by coastal currents along the Omani coast caused by the weakened southwest monsoon contributed to the maintenance of the high-salinity event. This prolonged high-salinity event reflects the upper-ocean responses to the monsoon change and may affect the regional hydrography and biogeochemistry extensively.

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Formation and spreading of Arabian Sea high-salinity water mass

Journal of Geophysical Research Atmospheres ◽

10.1029/1998jc900022 ◽

1999 ◽

Vol 104 (C1) ◽

pp. 1455-1464 ◽

Cited By ~ 116

Author(s):

S. Prasanna Kumar ◽

T. G. Prasad

Keyword(s):

Arabian Sea ◽

Water Mass ◽

High Salinity ◽

High Salinity Water ◽

Salinity Water

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The distribution of Recent Radiolaria in surficial sediments of the continental margin off northern Namibia

Journal of Micropalaeontology ◽

10.1144/jm.2.1.31 ◽

1983 ◽

Vol 2 (1) ◽

pp. 31-38 ◽

Cited By ~ 5

Author(s):

Simon Robson

Keyword(s):

Continental Margin ◽

High Salinity ◽

Cold Water ◽

Distribution Patterns ◽

Abundant Species ◽

High Salinity Water ◽

Low Salinity ◽

Apparent Correlation ◽

Benguela Current ◽

Salinity Water

Abstract. 47 Species of radiolaria have been identified from 30 surface sediment samples collected along transects across the continental margin of northern Namibia between the Kunene River and Walvis Bay. From the distribution patterns of the 24 most abundant species, it was possible to identify a warm water, high salinity population and a cold water, low salinity population. The distribution patterns of each population shows a close correspondence with the known positions of the Angola Current (warm, high salinity water) and the Benguela Current (cold, low salinity water) respectively. Two other trends are apparent from the overall radiolaria distribution; dilution of the nearshore samples by terrigeneous input and a strong preference for open ocean conditions. There is no apparent correlation with upwelling.

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Hydrographic survey over the Carlsberg Ridge in May 2012

10.5194/os-2019-62 ◽

2019 ◽

Author(s):

Hailun He ◽

Yuan Wang ◽

Xiqiu Han ◽

Yanzhou Wei ◽

Pengfei Lin ◽

...

Keyword(s):

Arabian Sea ◽

High Salinity ◽

Sea Water ◽

Phase Speed ◽

Thermocline Depth ◽

High Salinity Water ◽

Salty Water ◽

Hydrographic Survey ◽

Carlsberg Ridge ◽

Salinity Water

Abstract. In May 2012, we conducted a hydrographic survey over the Carlsberg Ridge in the northwest Indian Ocean. In this paper, we use these station data, in combination with some free-floating Argo profiles, to obtain the sectional temperature and salinity fields, and subsequently, the hydrographic characteristics are comprehensively analyzed. Through the basic T-S diagram, three salty water masses, Arabian Sea High-Salinity Water, Persian Gulf Water, and Red Sea Water, are identified. The sectional data show a clear ventilation structure associated with Arabian Sea High-Salinity Water. The 35.8 psu salty water sinks at 6.9° N and extends southward to 4.4° N at depths around the thermocline, where the thermocline depth is in the range of 100 to 150 m. This salty thermocline extends much further south than the climatology indicates. Furthermore, the temperature and salinity data are used to compute the absolute geostrophic current over the specific section, and the results show meso-scale eddy vertical structure different from some widely used oceanic reanalysis data. We also find a west-propagating disturbance at 6° N, and the related features are described in terms of phase speed, horizontal and vertical structures.

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Intra annual Variability of the Arabian Sea high salinity water mass in the South Eastern Arabian Sea during 2016 17

Defence Science Journal ◽

10.14429/dsj.69.14217 ◽

2019 ◽

Vol 69 (2) ◽

pp. 149-155

Author(s):

P. A. Maheswaran ◽

S. Satheesh Kumar ◽

T. Pradeep Kumar

Keyword(s):

Temporal Variability ◽

Arabian Sea ◽

Water Mass ◽

High Salinity ◽

High Salinity Water ◽

South Eastern ◽

Saline Waters ◽

Eastern Arabian Sea ◽

Salinity Water ◽

Spatio Temporal

Intra-annual variability of the Arabian Sea high salinity water mass (ASHSW) in the South Eastern Arabian Sea (SEAS) and Gulf of Mannar (GoM) are addressed in this paper by utilisng the monthly missions carried out onboard INS Sagardhwani during 2016-17. Our observations revealed that the ASHSW was evident along the SEAS irrespective of seasons, whereas in the GoM the presence of ASHSW was observed during winter. The processes such as downwelling/up-welling, coastal currents, intrusion of low saline waters, stratification are clearly affects the spreading of the ASHSW. The characteristics such as core salinity value, depth and thickness of ASHSW exhibited remarkable spatio-temporal variability. Lateral mixing with the low saline waters in the region during winter reduces its core salinity. The intrusion of low saline waters was clearly seen upto 15 ON but the intrusion of low saline waters is not flowing through the GoM. The interface between the ASHSW and the prevailing low saline waters showed strong horizontal gradients of salinity. The presence of the ASHSW makes difference in the SLD and the below layer gradient which is sufficient to complicate or influence sound transmission. The spatio temporal variability of the ASHSW and its acoustic relevance are documented in this paper.

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