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Sarantis Sofianos - One of the best experts on this subject based on the ideXlab platform.
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observations of the summer red Sea Circulation
Journal of Geophysical Research, 2007Co-Authors: Sarantis Sofianos, W E JohnsAbstract:[1] Aiming at exploring and understanding the summer Circulation in the Red Sea, a cruise was conducted in the basin during the summer of 2001 involving hydrographic, meteorological, and direct current observations. The most prominent feature, characteristic of the summer Circulation and exchange with the Indian Ocean, is a temperature, salinity, and oxygen minimum located around a depth of 75 m at the southern end of the basin, associated with Gulf of Aden Intermediate Water inflowing from the Gulf of Aden during the summer Season as an intruding subsurface layer. Stirring and mixing with ambient waters lead to marked increases in temperature (from 16.5 to almost 33°C) and salinity (from 35.7 to more than 38 psu) in this layer by the time it reaches midbasin. The observed Circulation presents a very vigorous pattern with strong variability and intense features that extend the width of the basin. A permanent cyclone, detected in the northern Red Sea, verifies previous observations and modeling studies, while in the central sector of the basin a series of very strong anticyclones were observed with maximum velocities exceeding 1 m/s. The three-layer flow pattern, representative of the summer exchange between the Red Sea and the Gulf of Aden, is observed in the strait of Bab el Mandeb. In the southern part of the basin the layer flow is characterized by strong banking of the inflows and outflows against the coasts. Both surface and intermediate water masses involved in the summer Red Sea Circulation present prominent spatial variability in their characteristics, indicating that the eddy field and mixing processes play an important role in the summer Red Sea Circulation.
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an oceanic general Circulation model ogcm investigation of the red Sea Circulation 2 three dimensional Circulation in the red Sea
Journal of Geophysical Research, 2003Co-Authors: Sarantis Sofianos, W E JohnsAbstract:[1] The three-dimensional Circulation of the Red Sea is studied using a set of Miami Isopycnic Coordinate Ocean Model (MICOM) simulations. The model performance is tested against the few available observations in the basin and shows generally good agreement with the main observed features of the Circulation. The main findings of this analysis include an intensification of the along-axis flow toward the coasts, with a transition from western intensified boundary flow in the south to eastern intensified flow in the north, and a series of strong Seasonal or permanent eddy-like features. Model experiments conducted with different forcing fields (wind-stress forcing only, surface buoyancy forcing only, or both forcings combined) showed that the Circulation produced by the buoyancy forcing is stronger overall and dominates the wind-driven part of the Circulation. The main Circulation pattern is related to the Seasonal buoyancy flux (mostly due to the evaporation), which causes the density to increase northward in the basin and produces a northward surface pressure gradient associated with the downward sloping of the Sea surface. The response of the eastern boundary to the associated mean crossbasin geostrophic current depends on the stratification and b-effect. In the northern part of the basin this results in an eastward intensification of the northward surface flow associated with the presence of Kelvin waves while in the south the traditional westward intensification due to Rossby waves takes place. The most prominent gyre Circulation pattern occurs in the north where a permanent cyclonic gyre is present that is involved in the formation of Red Sea Outflow Water (RSOW). Beneath the surface boundary currents are similarly intensified southward undercurrents that carry the RSOW to the sill to flow out of the basin into the Indian Ocean. INDEX TERMS: 4243 Oceanography: General: Marginal and semienclosed Seas; 4255 Oceanography: General: Numerical modeling; 4532 Oceanography: Physical: General Circulation; KEYWORDS: Red Sea, marginal Sea, Oceanic General Circulation Model, water mass formation
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an oceanic general Circulation model ogcm investigation of the red Sea Circulation 1 exchange between the red Sea and the indian ocean
Journal of Geophysical Research, 2002Co-Authors: Sarantis Sofianos, W E JohnsAbstract:[1] The mechanisms involved in the Seasonal exchange between the Red Sea and the Indian Ocean are studied using an Oceanic General Circulation Model (OGCM), namely the Miami Isopycnic Coordinate Ocean Model (MICOM). The model reproduces the basic characteristics of the Seasonal Circulation observed in the area of the strait of Bab el Mandeb. There is good agreement between model results and available observations on the strength of the exchange and the characteristics of the water masses involved, as well as the Seasonal flow pattern. During winter, this flow consists of a typical inverse estuarine Circulation, while during summer, the surface flow reverses, there is an intermediate inflow of relatively cold and fresh water, and the hypersaline outflow at the bottom of the strait is significantly reduced. Additional experiments with different atmospheric forcing (Seasonal winds, Seasonal thermohaline air–Sea fluxes, or combinations) were performed in order to assess the role of the atmospheric forcing fields in the exchange flow at Bab el Mandeb. The results of both the wind- and thermohaline-driven experiments exhibit a strong Seasonality at the area of the strait, which is in phase with the observations. However, it is the combination of both the Seasonal pattern of the wind stress and the Seasonal thermohaline forcing that can reproduce the observed Seasonal variability at the strait. The importance of the Seasonal cycle of the thermohaline forcing on the exchange flow pattern is also emphasized by these results. In the experiment where the thermohaline forcing is represented by its annual mean, the strength of the exchange is reduced almost by half.
W E Johns - One of the best experts on this subject based on the ideXlab platform.
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observations of the summer red Sea Circulation
Journal of Geophysical Research, 2007Co-Authors: Sarantis Sofianos, W E JohnsAbstract:[1] Aiming at exploring and understanding the summer Circulation in the Red Sea, a cruise was conducted in the basin during the summer of 2001 involving hydrographic, meteorological, and direct current observations. The most prominent feature, characteristic of the summer Circulation and exchange with the Indian Ocean, is a temperature, salinity, and oxygen minimum located around a depth of 75 m at the southern end of the basin, associated with Gulf of Aden Intermediate Water inflowing from the Gulf of Aden during the summer Season as an intruding subsurface layer. Stirring and mixing with ambient waters lead to marked increases in temperature (from 16.5 to almost 33°C) and salinity (from 35.7 to more than 38 psu) in this layer by the time it reaches midbasin. The observed Circulation presents a very vigorous pattern with strong variability and intense features that extend the width of the basin. A permanent cyclone, detected in the northern Red Sea, verifies previous observations and modeling studies, while in the central sector of the basin a series of very strong anticyclones were observed with maximum velocities exceeding 1 m/s. The three-layer flow pattern, representative of the summer exchange between the Red Sea and the Gulf of Aden, is observed in the strait of Bab el Mandeb. In the southern part of the basin the layer flow is characterized by strong banking of the inflows and outflows against the coasts. Both surface and intermediate water masses involved in the summer Red Sea Circulation present prominent spatial variability in their characteristics, indicating that the eddy field and mixing processes play an important role in the summer Red Sea Circulation.
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an oceanic general Circulation model ogcm investigation of the red Sea Circulation 2 three dimensional Circulation in the red Sea
Journal of Geophysical Research, 2003Co-Authors: Sarantis Sofianos, W E JohnsAbstract:[1] The three-dimensional Circulation of the Red Sea is studied using a set of Miami Isopycnic Coordinate Ocean Model (MICOM) simulations. The model performance is tested against the few available observations in the basin and shows generally good agreement with the main observed features of the Circulation. The main findings of this analysis include an intensification of the along-axis flow toward the coasts, with a transition from western intensified boundary flow in the south to eastern intensified flow in the north, and a series of strong Seasonal or permanent eddy-like features. Model experiments conducted with different forcing fields (wind-stress forcing only, surface buoyancy forcing only, or both forcings combined) showed that the Circulation produced by the buoyancy forcing is stronger overall and dominates the wind-driven part of the Circulation. The main Circulation pattern is related to the Seasonal buoyancy flux (mostly due to the evaporation), which causes the density to increase northward in the basin and produces a northward surface pressure gradient associated with the downward sloping of the Sea surface. The response of the eastern boundary to the associated mean crossbasin geostrophic current depends on the stratification and b-effect. In the northern part of the basin this results in an eastward intensification of the northward surface flow associated with the presence of Kelvin waves while in the south the traditional westward intensification due to Rossby waves takes place. The most prominent gyre Circulation pattern occurs in the north where a permanent cyclonic gyre is present that is involved in the formation of Red Sea Outflow Water (RSOW). Beneath the surface boundary currents are similarly intensified southward undercurrents that carry the RSOW to the sill to flow out of the basin into the Indian Ocean. INDEX TERMS: 4243 Oceanography: General: Marginal and semienclosed Seas; 4255 Oceanography: General: Numerical modeling; 4532 Oceanography: Physical: General Circulation; KEYWORDS: Red Sea, marginal Sea, Oceanic General Circulation Model, water mass formation
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an oceanic general Circulation model ogcm investigation of the red Sea Circulation 1 exchange between the red Sea and the indian ocean
Journal of Geophysical Research, 2002Co-Authors: Sarantis Sofianos, W E JohnsAbstract:[1] The mechanisms involved in the Seasonal exchange between the Red Sea and the Indian Ocean are studied using an Oceanic General Circulation Model (OGCM), namely the Miami Isopycnic Coordinate Ocean Model (MICOM). The model reproduces the basic characteristics of the Seasonal Circulation observed in the area of the strait of Bab el Mandeb. There is good agreement between model results and available observations on the strength of the exchange and the characteristics of the water masses involved, as well as the Seasonal flow pattern. During winter, this flow consists of a typical inverse estuarine Circulation, while during summer, the surface flow reverses, there is an intermediate inflow of relatively cold and fresh water, and the hypersaline outflow at the bottom of the strait is significantly reduced. Additional experiments with different atmospheric forcing (Seasonal winds, Seasonal thermohaline air–Sea fluxes, or combinations) were performed in order to assess the role of the atmospheric forcing fields in the exchange flow at Bab el Mandeb. The results of both the wind- and thermohaline-driven experiments exhibit a strong Seasonality at the area of the strait, which is in phase with the observations. However, it is the combination of both the Seasonal pattern of the wind stress and the Seasonal thermohaline forcing that can reproduce the observed Seasonal variability at the strait. The importance of the Seasonal cycle of the thermohaline forcing on the exchange flow pattern is also emphasized by these results. In the experiment where the thermohaline forcing is represented by its annual mean, the strength of the exchange is reduced almost by half.
Nadia Pinardi - One of the best experts on this subject based on the ideXlab platform.
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mediterranean Sea large scale low frequency ocean variability and water mass formation rates from 1987 to 2007 a retrospective analysis
Progress in Oceanography, 2015Co-Authors: Nadia Pinardi, Marco Zavatarelli, M Adani, Giovanni Coppini, Claudia Fratianni, Paolo Oddo, Simona Simoncelli, Marina Tonani, Vladislav Lyubartsev, Srdjan DobricicAbstract:Abstract We describe a synthesis of the Mediterranean Sea Circulation structure and dynamics from a 23-year-long reanalysis of the ocean Circulation carried out by Adani et al. (2011). This mesoscale permitting dynamical reconstruction of past ocean variability in the Mediterranean Sea allows the study of the time-mean Circulation and its low frequency, decadal, components. It is found that the time-mean Circulation is composed of boundary and open ocean intensified jets at the border of cyclonic and anticyclonic gyres. The large scale basin Circulation is generally characterized in the northern regions by cyclonic gyres and in its southern parts by anticyclonic gyres and eddy-dominated flow fields, with the exception of the Tyrrhenian and the northern Ionian Sea. The time-mean Tyrrhenian Sea Circulation is dominated by cyclonic gyres of different intensity and intermittency. The northern Ionian Sea Circulation, however, reverses in sign in two ten-year periods, the first in 1987–1996 and the second in 1997–2006, which is here called the Northern Ionian reversal phenomenon. This reversal is provoked by the excursion of the Atlantic-Ionian Stream from the middle to the northern parts of the basin. The decadal variability of other parts of the basin is characterized by changes in strength of the basin scale structures. The water mass formation rates and variability are dominated by event-like periods where the intermediate and deep waters are formed for 2–3 years at higher rates. The largest deep water formation events of the past 23 years occurred separately in the western and eastern Mediterranean basin: the first coincided with the Eastern Mediterranean Transient (Roether et al., 1996) and the second with the western Mediterranean deep water formation event in 2005–2006 (Smith et al., 2008). A new schematic of the basin-scale Circulation is formulated and commented.
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a nested atlantic mediterranean Sea general Circulation model for operational forecasting
Ocean Science, 2009Co-Authors: Paolo Oddo, Nadia Pinardi, M Adani, Claudia Fratianni, Marina Tonani, D PettenuzzoAbstract:Abstract. A new numerical general Circulation ocean model for the Mediterranean Sea has been implemented nested within an Atlantic general Circulation model within the framework of the Marine Environment and Security for the European Area project (MERSea, Desaubies, 2006). A 4-year twin experiment was carried out from January 2004 to December 2007 with two different models to evaluate the impact on the Mediterranean Sea Circulation of open lateral boundary conditions in the Atlantic Ocean. One model considers a closed lateral boundary in a large Atlantic box and the other is nested in the same box in a global ocean Circulation model. Impact was observed comparing the two simulations with independent observations: ARGO for temperature and salinity profiles and tide gauges and along-track satellite observations for the Sea surface height. The improvement in the nested Atlantic-Mediterranean model with respect to the closed one is particularly evident in the salinity characteristics of the Modified Atlantic Water and in the Mediterranean Sea level Seasonal variability.
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simulation of the mediterranean Sea Circulation from 1979 to 1993 part i the interannual variability
Journal of Marine Systems, 2002Co-Authors: E Demirov, Nadia PinardiAbstract:Abstract The interannual variability of the Mediterranean (MED) Circulation from 1979 to 1993 is studied with a 1° 8 × 1° 8 resolution OGCM. The surface forcing used is 6 hourly ECMWF (European Center for Medium Range Weather Forecast) reanalysis data. Two different periods in the surface forcing and model variability are identified during 1981–1993: the first, Period I (1981–1987) and the second, Period II (1988–1993). Changes in the model response between the two periods are driven by corresponding differences in the surface forcing, which presumably are a result of the decadal scale changes of the Northern Hemisphere (NH) atmospheric regimes, related to the intensification of North Atlantic Oscillation (NAO) at the end of the 1980s. During the second period (1988–1993), the Mediterranean Circulation reveals an overall weakening of the kinetic energy in the Western Mediterranean (WMED) basin and significant changes in the structure of Circulation in the Eastern basin. In the latter region, the anticyclonic activity increases in the southern Ionian and in the southern area of the mid-Mediterranean Jet. These anticyclonic eddies, present during different years of Period II with variable intensity, have an important impact on the transport of Modified Atlantic Waters (MAW) and Levantine Intermediate Waters (LIW) in the Eastern Mediterranean (EMED). This change of the Circulation modified the salinity and the amount of Levantine Intermediate Waters transported towards the Aegean Sea and the Adriatic Sea, which are important factors for deep water formation processes there. These model results are in good agreement with available observational results. The deep water formation event observed in the Aegean Sea [Science 271 (1996) 333] is produced by the model, but at a shallower depth. We interpret this event as the result of Circulation changes between Period I and Period II and anomalous surface atmospheric forcing over the Aegean Sea.
G. K. Korotaev - One of the best experts on this subject based on the ideXlab platform.
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Assimilation of the Data of Satellite Altimetry in an Eddy-Resolving Model of Circulation of the Black Sea
Physical Oceanography, 2004Co-Authors: V. L. Dorofeev, G. K. KorotaevAbstract:The data of satellite altimetry are used to simulate the Black-Sea Circulation. The altimetry data of the TOPEX/Poseidon and ERS satellites are prepared within the framework of the NASA Ocean Altimeter Pathfinder project. The additional data processing is performed to compute the dynamic level reflecting the Circulation of the Black Sea. The altimetry Sea-level is assimilated in an eddy-resolving model of Circulation of the Black Sea based on primitive equations. The accuracy of the obtained fields of temperature and salinity is estimated by comparing with the data of large-scale hydrographic surveys according to the ComSBlack program. The prognostic capabilities of the proposed model are estimated by comparing the obtained results with the fields computed with the help of assimilation of the altimetry data.
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Satellite altimetry observations of the Black Sea level
Journal of Geophysical Research: Oceans, 2001Co-Authors: G. K. Korotaev, Oleg A. Saenko, Chester J KoblinskyAbstract:The paper is devoted to the application of satellite altimetry from the TOPEX/Poseidon and ERS-1 missions to the Black Sea. We use the NASA Ocean Altimeter Pathfinder Project collinear data set and monthly climatic hydrography to restore the dynamical Sea level, that which connected with the Black Sea Circulation. Two realizations are created from collinear and grid data sets. The Black Sea hydrographic survey data collected by the Cooperative Marine Science Programme for the Black Sea are used for validation of both products. The estimated rms accuracy of the Black Sea dynamical level is about 3 cm. The grid data product is used for the analysis of Seasonal and mesoscale variability of the Black Sea level. The observations show that the Black Sea Circulation has strong Seasonal variation. It attenuates in summer to autumn and intensifies in winter to spring. This variability is accompanied by a western-phase propagation of the Sea level. A simple two-layer model of the wind-induced Circulation in the rectangular basin provides an interpretation of these results. It is shown that the Seasonal variability of the geostrophic Circulation is most likely produced by the annual changes of the wind stress curl. The western phase propagation is treated as the radiation of Rossby waves from the eastern coast of the basin. Typical periods of the mesoscale oscillations of the dynamical Sea level are estimated from the TOPEX/Poseidon altimeter time series in different parts of the Black Sea by means of a spectral analysis. The strongest mesoscale oscillations have periods of about 120 days and are located in the southeastern part of the basin, where the Rim Current bifurcates, and off the Crimean peninsula, where the Rim Current meanders as a result of the local orography.
Paolo Oddo - One of the best experts on this subject based on the ideXlab platform.
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mediterranean Sea large scale low frequency ocean variability and water mass formation rates from 1987 to 2007 a retrospective analysis
Progress in Oceanography, 2015Co-Authors: Nadia Pinardi, Marco Zavatarelli, M Adani, Giovanni Coppini, Claudia Fratianni, Paolo Oddo, Simona Simoncelli, Marina Tonani, Vladislav Lyubartsev, Srdjan DobricicAbstract:Abstract We describe a synthesis of the Mediterranean Sea Circulation structure and dynamics from a 23-year-long reanalysis of the ocean Circulation carried out by Adani et al. (2011). This mesoscale permitting dynamical reconstruction of past ocean variability in the Mediterranean Sea allows the study of the time-mean Circulation and its low frequency, decadal, components. It is found that the time-mean Circulation is composed of boundary and open ocean intensified jets at the border of cyclonic and anticyclonic gyres. The large scale basin Circulation is generally characterized in the northern regions by cyclonic gyres and in its southern parts by anticyclonic gyres and eddy-dominated flow fields, with the exception of the Tyrrhenian and the northern Ionian Sea. The time-mean Tyrrhenian Sea Circulation is dominated by cyclonic gyres of different intensity and intermittency. The northern Ionian Sea Circulation, however, reverses in sign in two ten-year periods, the first in 1987–1996 and the second in 1997–2006, which is here called the Northern Ionian reversal phenomenon. This reversal is provoked by the excursion of the Atlantic-Ionian Stream from the middle to the northern parts of the basin. The decadal variability of other parts of the basin is characterized by changes in strength of the basin scale structures. The water mass formation rates and variability are dominated by event-like periods where the intermediate and deep waters are formed for 2–3 years at higher rates. The largest deep water formation events of the past 23 years occurred separately in the western and eastern Mediterranean basin: the first coincided with the Eastern Mediterranean Transient (Roether et al., 1996) and the second with the western Mediterranean deep water formation event in 2005–2006 (Smith et al., 2008). A new schematic of the basin-scale Circulation is formulated and commented.
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a nested atlantic mediterranean Sea general Circulation model for operational forecasting
Ocean Science, 2009Co-Authors: Paolo Oddo, Nadia Pinardi, M Adani, Claudia Fratianni, Marina Tonani, D PettenuzzoAbstract:Abstract. A new numerical general Circulation ocean model for the Mediterranean Sea has been implemented nested within an Atlantic general Circulation model within the framework of the Marine Environment and Security for the European Area project (MERSea, Desaubies, 2006). A 4-year twin experiment was carried out from January 2004 to December 2007 with two different models to evaluate the impact on the Mediterranean Sea Circulation of open lateral boundary conditions in the Atlantic Ocean. One model considers a closed lateral boundary in a large Atlantic box and the other is nested in the same box in a global ocean Circulation model. Impact was observed comparing the two simulations with independent observations: ARGO for temperature and salinity profiles and tide gauges and along-track satellite observations for the Sea surface height. The improvement in the nested Atlantic-Mediterranean model with respect to the closed one is particularly evident in the salinity characteristics of the Modified Atlantic Water and in the Mediterranean Sea level Seasonal variability.
