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Numerical modelling of salinity variations due to wind and thermohaline forcing in the Persian Gulf
Abstract
Salinity is an important component of the marine system. Due to shallow nature of the Persian Gulf, the salinity has been influenced by both wind driven and surface thermohaline fluxes (heat and moisture fluxes). In this study, the seasonal distribution of salinity and its variations due to wind stress and thermohaline forcing are investigated by using a three-dimensional hydrodynamic model, Coupled Hydrodynamical–Ecological Model for Regional and Shelf Seas (COHERENS). The simulation results show that the salinity in the Persian Gulf experiences dramatic spatial and temporal variations. The influence of the thermohaline forcing is considerably more than the wind stress on the salinity. The effect of the surface thermohaline fluxes over the salinity field is generally to increase the salinity for almost all the water column during the year. This effect is high during September–November where the evaporative surface salinity flux dominates over inflow of low-salinity values of Indian Ocean Surface Water. The wind forcing at the most regions of the Persian Gulf, in particular at the United Arab Emirate (UAE) coast and Bahrain–Qatar shelf, freshens the water all the year round. The wind and thermohaline forcing in March–June have strong potential to generate stratification in salinity structure. The model predictions, which are successful in simulating many features of observed pattern, indicate that the surface water of the Gulf is saltier in winter than that in spring and early summer. Both heat fluxes and wind stress play an important role for this seasonal cycle of the surface salinity.
... Several regional modeling studies have been conducted to simulate and study the hydrodynamics of the Gulf. Most of these studies investigated the general circulation in the basin (Shenn-Yu et al., 1992;Sadrinasab and Kämpf, 2004;Kämpf and Sadrinasab, 2006;Yao and Johns, 2010a;Yao and Johns, 2010b;Hassanzadeh et al., 2011;Hosseinibalam et al., 2011;Pous et al., 2015;Al Azhar et al., 2016;Alosairi and Pokavanich, 2017;Layeghi et al., 2019;Al-Shehhi et al., 2021), while others examined the basin's response to winds (Thoppil and Hogan, 2010b;Hassanzadeh et al., 2011;Hosseinibalam et al., 2011;Pous et al., 2013b). Certain studies explored the role of tides (Azam et al., 2006;Pous et al., 2013a) and mesoscale processes (Thoppil and Hogan, 2010a), and others the heat, salinity, and freshwater budgets (Xue and Eltahir, 2015;Campos et al., 2020). ...
... Several regional modeling studies have been conducted to simulate and study the hydrodynamics of the Gulf. Most of these studies investigated the general circulation in the basin (Shenn-Yu et al., 1992;Sadrinasab and Kämpf, 2004;Kämpf and Sadrinasab, 2006;Yao and Johns, 2010a;Yao and Johns, 2010b;Hassanzadeh et al., 2011;Hosseinibalam et al., 2011;Pous et al., 2015;Al Azhar et al., 2016;Alosairi and Pokavanich, 2017;Layeghi et al., 2019;Al-Shehhi et al., 2021), while others examined the basin's response to winds (Thoppil and Hogan, 2010b;Hassanzadeh et al., 2011;Hosseinibalam et al., 2011;Pous et al., 2013b). Certain studies explored the role of tides (Azam et al., 2006;Pous et al., 2013a) and mesoscale processes (Thoppil and Hogan, 2010a), and others the heat, salinity, and freshwater budgets (Xue and Eltahir, 2015;Campos et al., 2020). ...
The contribution of surface and lateral forcing to the observed Arabian Gulf warming trend is studied based on the results of a high-resolution (1/100°, 60 vertical layers) MIT general circulation model (MITgcm) covering the period 1993–2021. The model validation against available observations reveals that the simulation satisfactorily reproduces the main features of the Arabian Gulf’s dynamics and their variability. We show that the heat content of the Arabian Gulf generally follows the reported variability of sea surface temperature, with significant increasing trends of 0.1 × 10⁷ J m⁻³ and 0.2°C per decade. The interannual variability of the heat content is dominated by the surface heat fluxes, while the long-term warming of the basin is primarily driven by lateral fluxes. The analyses of the heat exchanges through the Strait of Hormuz indicate a pronounced upward trend in the transported heat toward the Arabian Gulf, which is associated with an increase in both the volume and temperature of the exchanged waters. Considering the inflow and outflow in the Strait separately, the temperature increase is more prominent in the inflowing waters; however, the dominant factor driving the rising trend in heat content exchanges is the increase in the volume of waters being exchanged. This implies that the observed warming of the Arabian Gulf during the investigated period is directly related to the acceleration of its overturning circulation.
... Although river inflow may affect the water column structure locally, water parameters in our sampling area depend largely on the magnitude of oceanic water inflow, that varies throughout the year (Reynolds 1993). During early autumn (i.e. when most sea turtle samples were collected) surface water salinity and temperature ranged from 36.5 PSU to 38.5 PSU and from 27°C to 32°C, respectively, with both parameters increasing towards the northwest (Al Azhar et al. 2016;Hassanzadeh et al. 2011;Hume et al. 2018;Reynolds 1993). The nutrient-rich waters trapped near the Strait of Hormuz due to its shape, bathymetry, and wind regime (German & Elderfield 1990;Longhurst et al. 1995) may enhance diatom productivity, as was suggested in a study of the particularly abundant diatom communities found on olive ridleys from the Pacific coast of Costa Rica (Majewska et al. 2015c), a high productivity zone (Fiedler 2002). ...
... Although no correlation between nitrate and phosphate concentrations and diatom abundances was observed, it cannot be excluded that other nutrients or micro-elements associated with oceanic water influx influence sea turtle diatom productivity. In spring, salinity in the study region remains within the range of 36.5-38.5 PSU, while temperatures drop to 24-28°C (Al Azhar et al. 2016;Hassanzadeh et al. 2011;Hume et al. 2018;Reynolds 1993). This is consistent with temperature and salinity fluctuations observed during the current study (Table 2). ...
The current study investigated diatom communities on juvenile green turtles foraging in neritic habitats around five Iranian islands. The primary objectives were to (1) compare species composition, growth form structure, and abundance of diatom communities associated with sea turtles foraging within the restricted boundaries of local feeding pastures, and (2) assess the level of uniqueness of the epizoic diatom flora in comparison with biofilms growing on floating debris. All observations and diatom counts were performed using scanning electron microscopy. The effect of the sampling location was apparent among sea turtle samples and reflected in significantly different cell densities. Diatom abundances were significantly higher on sea turtles (758-1836 cells mm −2) than on floating debris samples (9-189 cells mm −2). Epizoic diatom communities were composed of 20 diatom taxa and dominated by erect forms belonging to the so-called 'marine gomphonemoids', Chelonicola and Poulinea, previously reported on sea turtles from other geographical regions. The diatom flora found on floating debris was composed of 21 taxa. Only four taxa, Amphora cf. bigibba, Cocconeis cf. neothumensis var. marina, Psammodictyon constrictum, and Tabularia affinis, were recorded from both sea turtles and floating debris samples, and none of these exceeded 4% of the average relative abundance on the sea turtle carapaces. The study reveals a clear substratum preference in sea turtle-associated diatoms, with no evidence for species turnover across the investigated region over different sampling seasons, thus confirming previous speculations that sea turtle diatom communities would show a high level of uniqueness and stability.
... Since the Fresnel reflection coefficients are function of the complex dielectric constant, I have applied the Ellison et al. model to its estimate at 5 GHz (Ellison et al., 1998Ellison et al., , 2003). The salinity and temperature data needed for the model were provided by using a 3-D numerical model described in our previous papers (Hassanzadeh et al., 2011;). The rest of this paper is organized as follows. ...
... ε 0 and t are calculated as follows: Ellison et al. were calculated the coefficients a i and b i for i ¼ 1, 2 by a least squares regressions analysis (Ellison et al., 1998Ellison et al., , 2003). Salinity and temperature data needed for calculating the complex permittivity at C-band were provided from our previous work (Hassanzadeh et al., 2011; Hosseinibalam et al., 2011). These data were simulated by using a 3-D hydrodynamic numerical model and validated by limited direct measurements in the Persian Gulf (see next section). ...
The knowledge of the sea surface emissivity can be used to design passive and active microwave sensors for ocean remote sensing applications. In this study, the variability of vertical and horizontal polarizations of Fresnel emissivity over the Persian Gulf water at 5 GHz in a nadir-viewing direction are investigated by using Fresnel's equations. Data sets used to compute Fresnel reflection coefficients were provided from our previous studies on hydrodynamic and electromagnetic properties of Persian Gulf water. The calculations indicated that spatial variability of Fresnel emissivity for both vertical and horizontal polarizations were relatively large compared to its temporal variability. The annual domain-averaged mean for vertical emissivity at the C- band was 0.3914, whereas for the horizontal polarization of the emissivity, it was 0.3645 in a nadir-viewing direction.
... The exchange flux is relatively weak in comparison to that of other similar semi-landlocked basins (e.g., Red Sea, Mediterranean Sea) and averages to about 0.15 Sv 19 . The Gulf already experiences extreme environmental conditions for a subtropical sea, with temperatures reaching 36 • C in summer and typical salinities of 42 psu in the southern shallows 15,20 . Therefore, the possibility that desalination activities may result in non-negligible, basin-wide salinity increases, with potentially negative environmental and economic impacts, should be carefully addressed. ...
The nations on the shoreline of the Arabian/Persian Gulf are the world’s largest users of desalination technologies, which are essential to meet their freshwater needs. Desalinated freshwater production is projected to rapidly increase in future decades. Thus, concerns have been raised that desalination activities may result in non-negligible long-term, basin-wide increases of salinity, which would have widespread detrimental effects on the Gulf marine ecosystems, with ripple effects on fisheries, as well as impacting the desalination activities themselves. We find that current yearly desalinated freshwater production amounts to about 2% of the net yearly evaporation from the Gulf. Projections to 2050 bring this value to 8%, leading to the possibility that, later in the second half of the century, desalinated freshwater production may exceed 10% of net evaporation, an amount which is comparable to interannual fluctuations in net evaporation. With the help of a model we examine several climatological scenarios, and we find that, under IPCC’s SSP5-8.5 worst-case scenarios, end-of-century increases in air temperature may result in salinity increases comparable or larger to those produced by desalination activities. The same scenario suggests a reduced evaporation and an increased precipitation, which would have a mitigating effect. Finally we find that, owing to a strong overturning circulation, high-salinity waters are quickly flushed through the Strait of Hormuz. Thus, even in the worst-case scenarios, basin-scale salinity increases are unlikely to exceed 1 psu, and, under less extreme hypothesis, will likely remain well below 0.5 psu, levels that have negligible environmental implications at the basin-wide scale.
... Our findings also showed that winter is the most suitable season for macroalgal growth and development along the eastern coasts of Qeshm Island. This result agreed well with previous work in the literature in which it was anticipated that due to more thorough mixing of the seawater during winter, the highest biomass of macroalgae was achieved in the Persian Gulf (37). Furthermore, the current finding showed that Padina spp. in Phaeophyta was the dominant species of the macroalgal; community at the studied sites (Table 2). ...
Aims: Monitoring variations in macroalgal assemblages is a crucial issue for the preservation and management program of coastal waters. This study was conducted to determine the seasonal and spatial distribution patterns, and composition of macroalgal communities along the eastern coasts of Qeshm Island, Iran.
Materials & methods: Seasonal sampling was conducted at three different sites of different tidal levels on the eastern coasts of Qeshm Island. Random samples of macroalgae were collected at three stations, seasonally. The species were identified and the dry weight of each species was used to calculate the macroalgae abundance. The Species richness and the Diversity indices were calculated to evaluate the distribution pattern and composition of the macroalgal community.
Findings: As a result, 51 species (4 Chlorophyta, 21 Phaeophyta, and 26 Rhodophyta) were identified. The seasonal and spatial dominant species were found to be Padina sp. and Hypnea sp., and a distribution pattern was seen to have increasing macroalgal biomass from the upper to lower intertidal level. The sampling sites shared more than 50% similarity of their macroalgal species, indicating a relatively homogeneous distribution. The highest (18.1±4.3 gr drywt m-2) and lowest (8.27±2.1 gr drywt m-2) mean of total seaweed biomass were recorded in winter and summer, respectively.
Conclusion: The assemblage composition of macroalgae significantly differs between hot and cold seasons, and there was no substantial compositional variation of seaweeds communities along the tidal gradient. The macroalgal distribution was largely homogeneous with no significant difference among the research areas at sampling seasons.
... The exchange flux is relatively weak in comparison to that of other similar semi-landlocked basins (e.g., Red Sea, Mediterranean Sea) and averages to about 0.15 Sv 19 . The Gulf already experiences extreme environmental conditions for a subtropical sea, with temperatures reaching 36 • C in summer and typical salinities of 42 psu in the southern shallows 15,20 . Therefore, the possibility that desalination activities may result in non-negligible, basin-wide salinity increases, with potentially negative environmental and economic impacts, should be carefully addressed. ...
The nations on the shoreline of the Arabian/Persian Gulf are the world’s largest users of desalination technologies, which are essential to meet their freshwater needs. Desalinated freshwater production is projected to rapidly increase in future decades. Thus, concerns have been raised that desalination activities may result in non–negligible long–term, basin–wide increases of salinity, which would have widespread detrimental effects on the Gulf marine ecosystems, with ripple effects on fisheries, as well as impacting the desalination activities themselves. We find that current desalinated freshwater production amounts to about 2% of the net evaporation from the Gulf. Projections to 2050 bring this value to 8%, leading to the possibility that, later in the second half of the century, desalinated freshwater production may exceed 10% of net evaporation, an amount which is comparable to interannual fluctuations in net evaporation. With the help of a model we examine several climatological scenarios, and we find that, under IPCC’s SSP5-8.5 worst–case scenarios, end–of–century increases in air temperature may result in salinity increases comparable or larger to those produced by desalination activities. The same scenario suggests a reduced evaporation and an increased precipitation, which would have a mitigating effect. Finally we find that, owing to a strong overturning circulation, high–salinity waters are quickly flushed through the Strait of Hormuz. Thus, even in the worst–case scenarios, basin–scale salinity increases are unlikely to exceed 1 psu, and, under less extreme hypothesis, will likely remain well below 0.5 psu, levels that have negligible environmental implications at the basin-wide scale.
... Moreover, salinity may reach 70 psu in shallow areas during summer [64]. Given the limited number of direct oceanographic observations in the Gulf, the analysis of the observed data shows that the geographical distribution of salinity in the Gulf varies significantly over time and space [65]. Figure 4 depicts the surface salinity observed during winter and summer at depths of 0-3 m published by Swift and Bower in 2003 [66]. ...
Whitings, the manifestation of high levels of suspended fine-grained calcium carbonate particles in the water, have been reported and studied worldwide. However, the triggering mechanism of whiting occurrences remains uncertain. The current study attempted to analyze potential factors that might account for whiting occurrences in a semi-enclosed gulf (namely the Arabian/Persian Gulf, hereinafter called the Gulf). First, spatial and temporal variability of whiting events and different potential driving factors (i.e., whiting seasonality, wind-induced mixing, sea surface temperature, and bathymetry) were explored and examined for five years (2015–2020). Second, as a general indicator of whiting occurrences in the Gulf, a whiting index (WI) was developed using time-series analysis and decision tree (DT) classification algorithm. Third, the correlation between the proposed WI and the spatial coverage of various whiting events was examined. Time-series analysis showed that whiting events during the winter season are associated with high winds that lasted for several days.
Nevertheless, whiting events were rarely observed despite high wind speed and increased potential for CaCO3 precipitation in summer. This finding suggests that wind-driven forces might be potential
sources for mixing water columns, resuspension of CaCO3 particles, and the appearance of whiting in the Gulf. The DT classification algorithm demonstrated that a minimum WI value of 1.1 can explain the initiation of most summer and winter whiting events. Furthermore, a Pearson correlation coefficient of 0.73 was measured between WI and the extent of whiting along the UAE and Qatar coastlines in the Gulf. The proposed WI shows a simple yet effective method for identifying and estimating the extent of whiting in the Gulf.
... پراکنش ریزموج بادهای مقایسه با بسیاری ارزیابی مطالعات سنج ها بویه توسط ایستگاهی مشاهدات با رادیومترها و دیگر و ها است شده انجام جهان سطح در هواشناسی ابزارهای (Bentamy et al., 1994;Ebuchi et al., 2002;Freilich and Dunbar, 1999;Masuko et al., 2000;Membery, 1983;Schroeder et al., 1982;Wentz, 1997;Wentz et al., 1982) . شده اصالح اند (Walmsley, 1988) رابطه . 1 نشان است تبدیل این دهنده (Benschop, 1996) ، (Stull, 1988) : (Hassanzadeh et al., 2011;Kämpf and Sadrinasab, 2005) . (Yamartino, 1984) محاسبه برای ...
... These mangroves exist in an extreme environment under an arid climate with hypersaline conditions (37.9-41.3 ppt) ( Hassanzadeh et al., 2011 ;Ibrahim et al., 2020 ;Moaddab et al., 2017 ), and without direct riverine input. The vegetation occupies alluvial and Solenchak soils in the area ( Mostafavi et al., 2004 ). ...
Climate change is a major threat to mangrove ecosystems worldwide but particularly those in arid regions that exist near the limit of tolerance to extremes in temperature, precipitation, and salinity. Here we examine Persian Gulf arid mangrove ecosystems from the Nayband and Mond Protected Area in the south-west region of Iran to determine the ability of tidal mangrove forests to respond to rapid urban and industrial development, sea-level rise (SLR), and temperature and precipitation changes. Sea level has been rising by approximately 4 mm yr⁻¹ in this region and might be intensified by subsidence on the order of 1–2 mm yr⁻¹ due to natural phenomena as well as anthropogenic activities associated with fluid extraction. We use remote sensing along with statistical analysis to effectively monitor mangrove area changes over 60 years and infer responses to past environmental trends. Our spatiotemporal analysis demonstrates expansion in some areas and reduction in others. NDVI (Normalized Difference Vegetation Index) results indicate that Nayband mangroves are healthy and expanded between the years of 1990 and 2002 which could be in response to rising temperatures and above-average precipitation. However, NDVI changes after 2002 demonstrate the mangrove health and area have decreased which could be in response to industrial and urban development that occurred immediately after 1997. The natural stresses in this extreme system are been exacerbated by climate change and anthropogenic pressures as such it is essential to develop ways to reduce vulnerability through strategic management planning.
... The Gulf basin has an average depth of about 35 m with the deepest point approximately at 107 m (Kämpf and Sadrinasab 2005). The circulation in the Persian Gulf is driven by wind-stress, surface buoyancy fluxes, freshwater runoff, water exchange through the Strait of Hormuz, and tides (Hassanzadeh et al. 2011;Pous et al. 2015;Mokhtari et al. 2015). ...
The main aim of the present study was to assess the pollution loading and ecological risk of toxicity levels in the surface sediment of the Persian Gulf. About 56 surface sediment samples were considered to determine the toxicity and the geochemical concentration of the heavy metals including 24 elements. The geochemical analysis revealed that among the measured elements, the highest mean concentration belongs to Mg (23,825 µg g–1) and the lowest value relates to Hg (0.017 µg g–1). The concentrations of the elements in the sediment showed that high enrichment of Fe and Al elements could be originated from anthropogenic sources. Based on the quantitative measurements of the geochemical indicators including geoaccumulation index (Igeo), potential ecological risk index (RI), and pollution load index (PLI), cobalt and cadmium were found to be in the high contamination and high-risk levels. Environmental modeling for overlaying of Igeo, RI, and PLI layouts, carried out in GIS to produce the spatial composite zoning of the study area, revealed the hotspots of composite contamination in the Khark, Kangan, and Hormuz regions affected by some oil and gas refining manufacturing, industrial zones and petrochemical units. Ultimately, the results of the statistical relationships confirmed the relatively strong and positive correlations between some major heavy metals (Al, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, V, and Zn) and clay fraction of sediments, Igeo and RI indicators.
... پراکنش ریزموج بادهای مقایسه با بسیاری ارزیابی مطالعات سنج ها بویه توسط ایستگاهی مشاهدات با رادیومترها و دیگر و ها است شده انجام جهان سطح در هواشناسی ابزارهای (Bentamy et al., 1994;Ebuchi et al., 2002;Freilich and Dunbar, 1999;Masuko et al., 2000;Membery, 1983;Schroeder et al., 1982;Wentz, 1997;Wentz et al., 1982) . شده اصالح اند (Walmsley, 1988) رابطه . 1 نشان است تبدیل این دهنده (Benschop, 1996) ، (Stull, 1988) : (Hassanzadeh et al., 2011;Kämpf and Sadrinasab, 2005) . (Yamartino, 1984) محاسبه برای ...
... It has an average depth of 50 m and a maximum depth of 90 m. The AG high salinity can reach 39-45 PSU, and its coasts and high sea surface temperatures that vary from 15 to 40 � C produce harsh environmental conditions (Hassanzadeh et al., 2011;Quigg et al., 2013;Naser, 2014). The SO is a strait that connects the AS with the AG and borders Oman on the south, U.A.E. on the west, and Iran on the north, with a surface area of about 181,000 km 2 , and a maximum depth of 3694 m. ...
Limited investigations into the role of dust deposition in enhancing phytoplankton growth in small and shallow water areas have been reported in the remote sensing literature. In this work, we show that phytoplankton growth was stimulated by nutrients supplied by dust deposition over sea water following three major dust storms that blew over the Arabian Gulf (AG) and the Sea of Oman (SO). Shallow water conditions, as those found in the AG and SO, limit convection and the role of mixing processes in supplying nutrients and in mediating bloom growth. Using satellite data, we analyzed three major dust events over the AG and SO in 2009, 2012, and 2015, and the phytoplankton bloom enhancement that ensued. We used the Mixed Layer Depth model to simulate water mixing and convection currents during and after the high dust events. We also applied the Regional Climate Model RegCM 4.5 to derive dust depositions patterns over AG and SO following the dust outbreak. Additionally, we computed potential requirement versus supply of nitrogen, phosphorus, and iron nutrients to support the observed phytoplankton growth using published nutrient data. Carbon to nitrogen to phosphorus, and carbon to chlorophyll ratios were obtained from in situ measurements in the AG and SO. Shallow depth mixed layers can likely still supply phosphate, but not enough nitrate and iron, leading to potential nitrate and dissolved iron limitations. Our work shows that dust storms are playing a significant role in providing nitrate supplies to support phytoplankton growth in shallow waters such as the AG and SO.
... Currently, the few available air-sea flux studies of the Gulf and Red Sea have used ships, buoys, coastal platforms, or oceanographic instruments that are sparsely distributed, and thus result in significant uncertainties in the heat flux estimates. For instance, studies have used the International Comprehensive Ocean-Atmosphere DataSet (ICOADS [31]) heat fluxes to force numerical models such as Hybrid Coordinate Ocean Model (HYCOM [32]) and the Coupled Hydrodynamical Ecological Model for Regional and Shelf Seas (COHERENS [33]) to simulate the Gulf surface and subsurface circulation [34][35][36]. ...
The air-sea heat fluxes in marginal seas and under extreme weather conditions constitute an essential source for energy transport and mixing dynamics. To reproduce these effects in numerical models, we need a better understanding of these fluxes. In response to this demand, we undertook a study to examine the surface heat fluxes in the Arabian Gulf (2013 to 2014) and Red Sea (2008 to 2010)-the two salty Indian Ocean marginal seas. We use high-quality buoy observations from offshore meteorological stations and data from two reanalysis products, the Modern-Era Retrospective analysis for Research and Applications version 2 (MERRA2) from the National Aeronautics and Space Administration (NASA) and ERA5, the fifth generation of the European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric reanalyses of global climate. Comparison of the reanalyses with the in situ-derived fluxes shows that both products underestimate the net heat fluxes in the Gulf and the Red Sea, with biases up to −45 W/m 2 in MERRA2. The reanalyses reproduce relatively well the seasonal variability in the two regions and the effects of wind events on air-sea fluxes. The results suggest that when forcing numerical models, ERA5 might provide a preferable dataset of surface heat fluxes for the Arabian Gulf while for the Red Sea the MERRA2 seems preferable.
... Also, at the northern Persian Gulf the evaporation exceeds the precipitation and freshwater discharge. Consequently, this has an additional effect on the altering of seasonal temperature and salinity patterns (Swift and Bower, 2003;Hassanzadeh et al., 2011;Hosseinibalam et al., 2011). Parts of the circulation in the Persian Gulf are slightly affected by tidal currents; tides are important for stirring and mixing waters vertically and on a horizontal scale of 10 km, but they only contribute to a small degree to the residual circulation of the Persian Gulf (Thoppil and Hogan, 2010a;Azizpour et al., 2016). ...
Using the long-term wind time series, coastal upwelling was investigated in the northern Persian Gulf. The shoreline was divided into 34 segments from NW to SE and the daily Ekman transport components were computed. Based on the Ekman transport components, a coastal upwelling index was calculated. Starting from these, in this paper we present, for the fi rst time in this region, the annual cycles of the coastal upwelling. The annual cycles revealed the most intense coastal upwelling in the central areas, located about 51° E - 53° E, including three peaks in June, November and February. In addition, a simple optimization procedure has been done to determine the best shoreline angle for the favorable conditions of coastal upwelling occurrence at each segment and month. To investigate the results, sea surface temperature (SST) and sea level anomalies (SLAs) were analyzed. A cross-correlation analysis was done on the daily time series and indicated that the SST decreases more in the segments with more intense coastal upwelling along the northern shoreline. The linear temporal trend was also applied to SLA gridded time series; the results show the sea level anomaly responses to wind-driven coastal upwelling.
... In temperate coastal waters, nitrogen and phosphorus concentrations of seawater are high in winter and low in summer (Martínez et al. 2012). Furthermore, Hassanzadeh et al., (2011) reported that seawater is well mixed during winter in the Persian Gulf. Hence, the result of this study which showed the highest biomass of macroalgae in winter may be attributable to increased nutrient availability in this season. ...
This study investigates the spatial and temporal variation of intertidal macroalgae along the eastern coasts of Qeshm Island, Persian Gulf, Iran. Monthly sampling of abundance, biomass, richness and diversity of macroalgae at three intertidal levels was carried out at two different sites during 1 year. The samples were collected every month using quadrats (0.5 × 0.5 m) from October 2012 to September 2013. The species dry weight was applied to examine changes in biomass and assemblage composition of intertidal macroalgae using univariate and multivariate analyses. A total of 42 seaweed species (10 Chlorophyta, 9 Phaeophyceae, and 23 Rhodophyta) were identified. The results confirmed a temporal pattern in the growth of the algal species which also showed a biomass zonation pattern from upper to lower intertidal. The annual mean biomass of macroalgae was highest in winter (29.3 ± 9.8 g dry wt m−2) and the lowest in autumn (17.3 ± 13.5 g dry wt m−2). The annual dominant species by biomass was Padina sp. followed by Padina australis. The most common species in the area, during the sampling period include Ulva intestinalis, Ulva lactuca, Palisada perforata and Padina sp. According to the similarity percentages analysis (SIMPER), the species Ulva intestinalis, Dictyosphaeria cavernosa (Chlorophyta), Padina australis (Phaeophyceae), Champia spp., Centroceras clavulatum and Palisada perforata (Rhodophyta) were responsible for the most dissimilarity of species composition between four seasons during the sampling period. BIOENV analysis indicated that the main environmental factors structuring macroalgal community at the study area were TDS and pH. The simple macroalgae community on the eastern coast of Qeshm Island and absence of slow-growing perennial macroalgae, such as members of the Sargassaceae, known from the lower shore at other intertidal localities along the island’s coast might relate to the predominantly unsuitable sandy-stony substrates unsuitable for their colonization and the unfavourable impact upon them of urbanization.
... We use this scheme to avoid the numerical dissipation caused by the upwind scheme and the false direct transport brought about by the Lax-Wandroff scheme, and to improve the calculation accuracy. The model is initialized in December, since the seawater is well mixed in winter [8,9], using uniform temperature and salinity fields with the values of 19°C and 38 psu. We utilize five sigma layers in the vertical direction with the Cartesian grid spacing of Δx = 6865 m (from the East to the West) and Δy = 7600 m (from the North to the South). ...
The Persian Gulf ecosystem is facing a variety of stresses as a result of being located within the richest oil province in the world, which hosts more than 67 % of the world oil reserve. In this paper, the distribution of oil pollution on the surface layer of the Persian Gulf is predicted for the different months after the release, based on the Coupled Hydrodynamical Ecological model for Regional Shelf seas (COHERENS). An Eulerian model for the Persian Gulf is set up using the Cartesian coordinate in the horizontal direction, and the sigma coordinate in the vertical direction. Based on this model, our analysis and simulation results indicate that the winds lead to diffusion of the contaminant concentration in the direction of the Arabian coast from the initial position of the spill. The results of this study can be used to provide appropriate solutions for preventing oil from spreading further in the region.
... The basin has an average depth of about 35 m, the deepest water approximately at 107 m (K€ ampf and Sadrinasab, 2005). The circulation in the Persian Gulf is driven by wind-stress, surface buoyancy fluxes, fresh water runoff, water exchange through the Strait of Hormuz, and tides (Hassanzadeh et al., 2011;Pous et al., 2015). In this study, we focused on the northern part of the Persian Gulf defined approximately by the Exclusive Economic Zone (EEZ) of I.R.Iran, and based on the availability of data on oil spill events. ...
... In the south, Iran has a coastline of approximately 5000 km lying within the Persian Gulf and the Gulf of Oman (Dibajnia et al. 2012), to which it is connected through the narrow Strait of Hormuz. The Persian Gulf is a semi-enclosed and evaporative marginal sea with a mean depth of about 35 m and dotted by many small islands (Hassanzadeh et al. 2011, Kourosh Niya et al. 2013. In comparison, the Gulf of Oman is connected to the Indian Ocean and provides direct access to open seas (Pak and Farajzadeh 2007). ...
... In the south, Iran has a coastline of approximately 5000 km lying within the Persian Gulf and the Gulf of Oman (Dibajnia et al. 2012), to which it is connected through the narrow Strait of Hormuz. The Persian Gulf is a semi-enclosed and evaporative marginal sea with a mean depth of about 35 m and dotted by many small islands (Hassanzadeh et al. 2011, Kourosh Niya et al. 2013. In comparison, the Gulf of Oman is connected to the Indian Ocean and provides direct access to open seas (Pak and Farajzadeh 2007). ...
In this study, a revised checklist of macroalgae of Iran with an updated nomenclature and taxonomy has been compiled based on published records. Using currently accepted names, 309 species and infraspecific taxa of macroalgae have been identified to date, including 78 Chlorophyta (within 15 families), 70 Ochrophyta (Phaeophyceae; within 7 families) and 161 Rhodophyta (within 30 families). The brown alga Sargassum with 25 taxa was the most diverse genus, and the Rhodomelaceae (Rhodophyta) with 36 taxa was the most species-rich family. The Cheney ratio of 3.4 and the species composition of brown seaweeds suggest that the Iranian marine algal flora is warmerate. Sørensen similarity indices were used to compare the marine algal flora of Iran with that of Saudi Arabia within the Persian Gulf and the Sultanate of Oman within the Gulf of Oman. The algal diversity of the Iranian coast within the Gulf of Oman is less than that within the Persian Gulf, and this difference is attributed to undercollecting. Given that this is the first inclusive checklist of macroalgae of Iran, covering the coast lying within the Persian Gulf and the Gulf of Oman, it could serve as a foundation for future phycological and biogeographical studies of the taxa in the country and the region.
... However, seas with very low salinity (from fresh to [12][13], which is about one third of the typical salinity of seawater [35], show low salinity variation with depth, so the discharge rate from rivers controls the monthly variations in surface salinity. Other relevant effects are surface-thermohaline fluxes (heat and moisture fluxes) and wind stress, which increase the salinity for almost the entire water column during the year, generating stratification in the salinity structure [62]. ...
Engineered nanoparticles (ENPs) are increasingly being incorporated into commercial products. A better understanding is required of their environmental impacts in aquatic ecosystems.This review deals with the ecotoxicity effects of silver and gold ENPs (AgNPs and AuNPs) in aquatic organisms, and considers the means by which these ENPs enter aquatic environments, their aggregation status and their toxicity. Since ENPs are transported horizontally and vertically in the water column, we discuss certain factors (e.g., salinity and the presence of natural organic materials), as they cause variations in the degree of aggregation, size range and ENP toxicity. We pay special attention to oxidative stress induced in organisms by ENPs.We describe some of the main analytical methods used to determine reactive oxygen species, antioxidant enzyme activity, DNA damage, protein modifications, lipid peroxidation and relevant metabolic activities. We offer an overview of the mechanisms of action of AgNPs and AuNPs and the ways that relevant environmental factors can affect their speciation, agglomeration or aggregation, and ultimately their bio-availability to aquatic organisms.Finally, we discuss similarities and differences in the adverse effects of ENPs in freshwater and salt-water systems.
... In addition, it is not possible to obtain typical oceanic flows using the analytic solutions of the equations of motion. Hence, numerical models and methods provide the only useful, global view of currents and water masses in oceans (Zhang et al. 2011, Hassanzadeh et al. 2010, Rennie et al. 2009, Ohashi et al. 2009). ...
In this study, the Navier-Stokes equations that embrace conservation equations of momentum, volume, heat and salt are solved by using a 3-D numerical model. Then, based on the values obtained, the structure and variability of the outflow/inflow between the Persian Gulf and the Gulf of Oman is investigated. The basic equations are cast in a bottom-following, sigma coordinate system which greatly simplifies the numerical solution. Conservative finite difference methods are used to discretise the mathematical model in space. The model results, which are in agreement with limited direct measurements in the Strait, show a volume transport of deep outflow and a near-surface outflow from the Persian Gulf to the Gulf of Oman through the southern part of the Strait. About 65% of total outflow occurs in the bottom layer (40 m to the bottom) and 35% in the upper layer (from the surface to 40 m deep) during the year. The annual mean of surface inflow from the Gulf of Oman to the Persian Gulf, which occurs within the northern part of the Strait is about 0.2 Sv. The net volume transport annual mean through the Strait into the Persian Gulf is about 0.03 Sv. Strong temperature and density contrasts between bottom and surface layer waters are established in spring and summer. These are more pronounced in the southern part of the Strait. In the northern part of the Strait, the salinity contrast is nearly constant, but in the southern half it varies significantly during the year.
The Strait of Hormuz, as a crucial link between the Persian Gulf and the Gulf of Oman, exhibits complex and distinct currents that are influenced by the connection of saline waters from the Persian Gulf and the Gulf of Oman. These currents contribute to the formation of seasonal eddies, influencing the deviation and dissipation of sound energy and causing notable changes in sound speed profiles in the region. This study utilized the ROMS 3D software to simulate variable circulation patterns and the development of mesoscale eddies in the Persian Gulf based on data from 2009. The simulations, conducted with a resolution of approximately 3 km and 16 layers at the sigma level, revealed a correlation between fluctuations in wind stress and variations in flows within the Strait of Hormuz. The exchange circulation induced by wind stress led to local instability and the formation of cyclonic eddies, particularly prominent in August. Following the simulations, acoustic modeling was performed using parabolic equations and the RAMGEO model. The study focused on frequencies of 100 and 500 Hz, covering a transmission range of 10 km at six stations within the Strait of Hormuz. Sound sources were strategically placed in the surface layer, thermocline layer, and homogeneous layer near the seabed. Analysis of the two-dimensional outputs of transmission loss indicated that the position of the sound source near the seabed had the most significant impact, followed by the thermocline layer and the surface layer.
Lower Valanginian oyster mass occurrences (OMOs) from the Neuquén Basin of Argentina are analyzed using a multidisciplinary approach, including the description of their sedimentological signature and stratigraphic contacts, assessment of taphonomical attributes, and paleontological and paleoecological characteristics. These OMOs present a wide distribution in the study area, with lateral continuity for at least 2.5 km and up to 12 m thick. They occur within a single stratigraphic interval, constrained in terms of sequence stratigraphy and biostratigraphy. Three stacked tabular OMOs separated by mudstone levels were recorded in all the studied localities. The associated lithofacies point to a mainly outer ramp paleoenvironment, below storm wave base and occasionally disturbed by exceptional, distal storm flows. Internally, the OMOs share a common vertical trend characterized, from base to top, by a gradual increase in oyster abundance and a transition from mainly reclining, disarticulated oysters to articulated,
cementing oysters conforming build-ups. Hence, a mainly biogenic origin is proposed, with autobiostromes grading vertically to bioherms. This vertical trend was interpreted in terms of development stages, namely, colonization, expansion, climax and extinction, which were in turn related to specific paleoenvironmental controls. Particularly, the OMOs establishment and development were associated to low sedimentation rates, salinity fluctuations and high nutrient input as a result of high primary productivity. At a larger scale, the overall paleoenvironmental conditions and subtropical geographical position of the basin were detrimental for most reef builders typical of the Cretaceous period (e.g., corals, sponges, rudists), and could have favored oyster proliferation and OMOs development instead.
For the microwave region of the electromagnetic spectrum, unlike visible light, the imaginary part of the refractive index can be significant, in which case it cannot be neglected. A well-known empirical model is not available for the direct calculation of the complex refractive index of seawater at the microwave region. However, based on the relationship between the refractive index and the permittivity, and by using the models provided for the seawater permittivity at the microwave frequencies the refractive index can be calculated. In this work, complex refractive index and normal reflectivity of Persian Gulf water at the C-band (5 GHz) have been calculated by using electromagnetic equations. The complex permittivity required for computing these parameters has been calculated from the Ellison's empirical model with measured input data. Calculations showed that the annual mean of basin-averaged of real and imaginary parts of the refractive index is 6.074 and 0.415, respectively. The relative spatial and temporal variability of the imaginary part of the refractive index is considerably stronger than its real counterpart. In all seasons, the reflection coefficient at the nadir in the western half of the Gulf is slightly higher than the eastern half and it has a minimum value of 0.5230 over the southeast waters in the summer and a maximum value of 0.5250 over the northwest waters of the Gulf Persian in winter.
The refractive index is one of the important inherent optical properties of seawater. Accurate knowledge of the refractive index is necessary for different scientific domains. In this study, the refractive index of Persian Gulf water within the visible light region is investigated by using Seaver–Millard algorithm. Input data for the model calculations are temperature, salinity, and pressure. Salinity and temperature data were obtained from World Ocean Atlas 2013 (WOA13). The Gulf water density, which is required to determine the pressure, was calculated from the UNESCO International Equation of State. The calculations showed that annual mean values of the index of refraction on the Persian Gulf surface at the wavelengths of \( 0.5\,\upmu{\text{m}} \), \( 0.6\,\upmu{\text{m}} \), and \( 0.7\,\upmu{\text{m}} \) are 1.34181, 1.33795, and 1.33540, respectively. These values vary by about 0.0015 due to significant variations in salinity and temperature, which are mainly caused by the influence of factors such as seasonal changes in the weather, inflow seasonal variation of low-salinity surface water from the Indian Ocean into the Gulf through the Strait of Hormuz, and the turbulence mixing processes of solar heating. The refractive index generally decreases from the head of the Gulf toward Strait of Hormuz all year round and increases from the surface to the bottom in the spring and summer.
The brightness temperature is the principle parameter detected by passive microwave radiometers. The radio frequency interference at L-band radiometers (e.g., SMOS, Aquarius and SMAP) impacts the quality of brightness temperature detection in many parts of the world such as the Middle East and the Persian Gulf. In the present work, vertical and horizontal polarizations of brightness temperature over flat surface water of Persian Gulf at L-band were calculated by using physical computations and an empirical model. For this purpose, Rayleigh–Jeans radiation law and Fresnel reflection equations were used and complex permittivity was calculated by Blanch and Aguasca model. Input data for the model calculations are temperature and salinity that were provided from World Ocean Atlas 2013. The calculations showed that the brightness temperature distribution in the Persian Gulf experiences significant spatial and seasonal variations. At nadir incidence angle, the vertical and horizontal components of brightness temperature over the Persian Gulf vary in the range 90.5–96.5 °k and 85.5–90.2 °k, respectively. At off-nadir incidence angle, the temporal variability pattern of brightness temperature horizontal polarization is similar to its vertical counterpart but the difference between them significantly increases.
A precise knowledge of the complex permittivity of water is essential for microwave remote sensing applications in physical and optical oceanography. In the present work, the spatial and seasonal variability of real and imaginary parts of Persian Gulf permittivity at the C-band (5 GHz), which has not been previously investigated, are computed by a numerical model and an experimental model. The dielectric constant distribution in the Persian Gulf experiences relatively significant seasonal variations and changes by −1.08 during January–July. The spatial variability of both the dielectric constant and loss are weaker in winter and autumn compared to spring and summer due to seasonal changes in the weather and turbulence mixing processes. Lateral stratification of imaginary permittivity is stronger than real permittivity and varies from 31 to 37 during the year with the highest variability in summer.
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[superscript −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[superscript −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[superscript −1], with a net influx of water equivalent to a Persian Gulf–averaged precipitation rate of 1.6 m yr[superscript −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.
[1] The exchange between the Persian (Arabian) Gulf and the Indian Ocean is investigated using hydrographic and moored acoustic Doppler current profiler data from the Straits of Hormuz during the period December 1996 to March 1998. The moored time series records show a relatively steady deep outflow through the strait from 40 m to the bottom with a mean speed of approximately 20 cm/s. A variable flow is found in the upper layer with frequent reversals on timescales of several days to weeks. The annual mean flow in the near-surface layer is found to be northeastward (out of the Persian Gulf) in the southern part of the strait, suggesting a mean horizontal exchange with the Indian Ocean that is superimposed on the vertical overturning exchange driven by evaporation over the gulf. The salinity of the deep outflow varies from 39.3 to 40.8 psu with highest outflow salinities occurring in the winter months (December–March). The annual mean deep outflow through the strait is estimated to be 0.15 ± 0.03 Sv. Calculation of the associated heat and freshwater fluxes through the strait yields estimates for the annual heat loss over the surface of the gulf of −7 ± 4 W/m2 and an annual water loss (E-P-R) of 1.68 ± 0.39 m/yr. These values are shown to be in relatively good agreement with climatological surface fluxes derived from the Southampton Oceanography Centre global flux climatology after known regional biases in the radiative budget are taken into account.
The results from a∼1km resolution HYbrid Coordinate Ocean Model (HYCOM), forced by 1/2° Navy Operational Global Atmospheric Prediction System (NOGAPS) atmospheric data, were used in order to study the dynamic response of the Persian Gulf to wintertime shamal forcing. Shamal winds are strong northwesterly winds that occur in the Persian Gulf area behind southeast moving cold fronts. The period from 20 November to 5 December 2004 included a well defined shamal event that lasted 4–5 days. In addition to strong winds (16ms−1) the winter shamal also brought cold dry air (Ta=20°C, qa=10gkg−1) which led to a net heat loss in excess of 1000Wm−2 by increasing the latent heat flux. This resulted in SST cooling of up to 10°C most notably in the northern and shallower shelf regions. A sensitivity experiment with a constant specific humidity of qa=15gkg−1 confirmed that about 38% of net heat loss was due to the air–sea humidity differences. The time integral of SST cooling closely followed the air–sea heat loss, indicating an approximate one-dimensional vertical heat balance. It was found that the shamal induced convective vertical mixing provided a direct mechanism for the erosion of stratification and deepening of the mixed layer by 30m. The strong wind not only strengthened the circulation in the entire Persian Gulf but also established a northwestward flowing Iranian Coastal Current (ICC, 25–30cms−1) from the Strait of Hormuz to about 52°E, where it veered offshore. The strongest negative sea level of 25–40cm was generated in the northernmost portion of the Gulf while the wind setup against the coast of the United Arab Emirates established a positive sea level of 15–30cm. The transport through the Strait of Hormuz at 56.2°E indicated an enhanced outflow of 0.25 Sv (Sv≡106m3s−1) during 24 November followed by an equivalent inflow on the next day.
Methods used for the solution of hydrodynamic governing equations in
numerical models of the atmosphere are discussed. In particular grid
point finite difference methods and problems and methods used for time
and horizontal space differencing are covered. Specific problems
relating to the numerical solution of the advection and gravity wave
equations are discussed.
1] The nature and circulation of water masses in the Persian/Arabian Gulf (hereinafter referred to as the Gulf) is investigated by examination of a historic database of hydrographic observations. The densest water forms in winter at the northern end of the Gulf rather than along the warmer southern and western coasts. With the exception of small amounts of water directly above the seafloor, most water flowing out of the Gulf mixes across a density front that separates Gulf Deep Water within the Gulf from the Indian Ocean Surface Water (IOSW). Contrary to previous inferences, the seasonally variable incursion of IOSW into the Gulf peaks in late spring. This timing may be due to seasonal changes in sea surface slope driven by variations in evaporation rate. In order to explain mooring results published elsewhere that show relatively small seasonal changes in the volume flux through the Strait of Hormuz (hereinafter referred to as the Strait), we suggest that this flux is driven by the difference between the density of Gulf Deep Water in the interior of the basin and water at comparable depths outside the Gulf. This density difference varies less than 15% during the year. High rates of vertical mixing in the Strait extend about 200 km westward in response to topographic constriction of tidal flows by islands and shoals.
The use of numerical modeling in oil spill incidents is a well established technique that has proven to provide cost-effective
and reasonable estimates of oil surface drift. Good predictability of such models depends highly on the quality of the input
data of the incident and on the model calibration effort. This paper presents the results of simulating oil spillage trajectory
in the Arabian (Persian) Gulf. The study employed a 3-D rectilinear hydrodynamic model combined with oil spill model. Typical
representative environmental conditions of the Arabian Gulf were first setup into a hydrodynamic circulation model using data
from various sources. The performance of the hydrodynamic model was then tested against measurements of tidal fluctuation
and sea currents at selected locations. The spill analysis model was setup using the flow field produced from the hydrodynamic
simulation and its performance was further validated against documented events of Al-Ahmadi historical oil spill crisis in
the Gulf. The comparison of the actual and simulated oil spill drift was found reasonably acceptable allowing for further
application in risk assessment studies in UAE Coastal water and in the entire Arabian Gulf as well.
Temperature-salinity-depth profile data were obtained for the Persian Gulf, Southern Red Sea and parts of the Arabian Sea from the Master Oceanographic Data Set (MOODS), located at the U. S. Naval Oceanographic Office (NAVOCEANO), Stennis Space Center, Mississippi. These data were used as part of a physical oceanographic study of the Red Sea and Persian Gulf outflows. This report documents the organization of the data set and the method of quality control used to eliminate unrealistic data. Also, it provides a summary in graphic form of the hydrographic observations. Funding was provided by the Office of Naval Research under Contract No. N00014-95-1-0284.
We employ a three-dimensional hydrodynamic model (COHERENS) in a fully prognostic mode to study the circulation and water mass properties of the Persian Gulf – a large inverse estuary. Our findings, which are in good agreement with observational evidence, suggest that the Persian Gulf experiences a distinct seasonal cycle in which a gulf-wide cyclonic overturning circulation establishes in spring and summer, but this disintegrates into mesoscale eddies in autumn and winter. Establishment of the gulf-wide circulation coincides with establishment of thermal stratification and strengthening of the baroclinic exchange circulation through the Strait of Hormuz. Winter cooling of extreme saline (>45) water in shallow regions along the coast of United Arab Emirates is a major driver of this baroclinic circulation.
A model that predicts tidal elevations and flow velocities is developed and applied to the Persian Gulf. The model uses finite difference techniques applied to two-dimensional spherical-coordinate equations that govern tidal movement in coastal regions. Because of the importance of the Gulf to the shipping and fishing industries, it is necessary to be able to predict tidal elevations and flows at many near-shore locations. However, it would be impractical to use a very fine finite difference grid over the whole Gulf, because of its size. A technique is developed for nesting a fine grid within a coarse grid, so that important areas can be modelled more accurately.
A two-week cruise in the Persian Gulf during August, 1948, by several ships resulted in the collection of a large amount of information about the sediments and water characteristics. Because the area is a geosyncline (long narrow trough of thick sediments), the new data serve to test some concepts of sedimentation in geosynclines. The water is of high temperature but also of such high salinity that Persian Gulf water sinks and flows out of the Gulf beneath incoming surface water of the Indian Ocean. The high temperature and salinity aid removal of calcium carbonate by mollusks, leading to a dominance of shell fragments in the sediments. Oolites are common in the entrance area, but more soluble minerals such as gypsum and halite are present only in shallow marginal lagoons Non-calcareous detrital sediment is contributed mostly by rivers at the head of the Gulf, though wind-derived sediment is locally important. The non-calcareous detrital fraction is mostly fine-grained with light minerals dominated by quartz, and heavy minerals dominated by tough resistant species such as leucoxene, zircon, magnetite, sphene, epidote, and garnet. Contours of grain size, calcium carbonate content, and water salinity are more or less parallel with the axis of the Gulf, rather than transverse as might be expected of a geosyncline having its chief source of detrital sediment at one end and its opening to the ocean at the other end. The high percentage of calcium carbonate, quartz, and resistant heavy minerals is characteristic of an area of slow deposition and does not fit t e common concept of geosynclinal sediment, non-calcareous graywacke. Mesozoic and Tertiary strata of the geosyncline also contain much limestone. Evaporites, common in the older rocks, would be more widely deposited at present if the entrance strait were to become shallower than now by diastrophic uplift. A higher organic content, probably characteristic of the Mesozoic and Tertiary oil source beds, would exist in present sediments if the strait were more open and if the climate were cooler and wetter than now.
The determination of the surface fluxes of momentum, heat, and mass on temporal and spatial scales is of direct importance to two major fields of geophysics: air-sea interaction and remote sensing. Although the surface fluxes, in a sense, represent the common link between these two growing fields, the disciplines of air/sea interaction and remote sensing have, in the most part, evolved independently. Only recently, with the promise of continuous operational satellite retrievals of directly measured surface data, have the two disciplines begun to merge. Research programs are now being conducted with the intent of describing geophysical variables with remote sensing data in addition to understanding the physics of ocean surface scattering, the processes involved in describing the air-sea exchange rates, and the statistical character of the surface wave state. The outcome of such joint research efforts is intended to provide higher quality monitoring and forecasting of the marine environment through remote sensing techniques.
A three-dimensional hydrodynamic model is developed to study the
circulation in the Arabian Gulf. The model contains realistic basin
geometries and bathymetries of the Arabian Gulf and a good portion of
the Gulf of Oman and is driven by monthly climatological winds,
evaporation, and net ocean heat gain in both gulfs and the Shatt-al-Arab
discharge. It is found that the cyclonic circulation in the southern
portion of the gulf is primarily driven by the evaporation-induced
freshening from the Strait of Hormuz. In the northwestern corner of the
gulf, the Shatt-al-Arab discharge maintains the cyclonic circulation,
which would otherwise be anticyclonic. The northwestward intrusion of
fresher water along the Iranian coast is weakened by northwesterly winds
in winter but strengthens and extends almost to the head of the gulf in
summer owing to the warming of the Gulf of Oman waters, the development
of the summer thermocline in the Arabian Gulf, and diminishing winds.
The southward coastal current along the Arabian coast is most prominent
between the head of the gulf and Qatar. The model also predicts a strong
southward coastal jet east of Qatar which is primarily wind driven. No
similar coastal jet can be developed in the Gulf of Salwa, west of
Qatar.
Thirty-four years of data (1967–2000) are used to investigate the variability pattern relevant to air–sea interaction in the Persian Gulf. The patterns are derived using statistical techniques, such as empirical orthogonal function (EOF) and singular value decomposition (SVD). Statistical analysis methods are applied to determine the coupled modes of variability of monthly sea surface temperature (SST) and sea level pressure (SLP). The significant of the air–sea interaction is found by a strong resemblance between EOF and SVD eigenvectors and expansion coefficients of SST and SLP. We find that the four leading EOF patterns of SST together account for 99.8% of the total monthly SST variance and 94.4% of the SLP variance. The zero contour in the first SST EOF identified the front which separates the Persian Gulf cyclonic gyres.The SVD modes provide more information on the coupling between the fields than the modes obtained by EOF methods. Lagged correlation analysis between SVD1(SLP) and SVD1(SST) indicates that the coupling is strongest when SLP leads SST by −12, −6, 6 and 12 months. Therefore, the first mode of the SVD analysis seems to depict an air-to-sea forcing, in which the sea response to the atmospheric changes appears with an semiannual and interannual time lag.The two leading SVD modes of variability of the coupled SST and SLP fields account for 99.6% of the total variance. The main patterns of both variables of variability of both variables independently provide considerable information on the coupling, but only one of the two variables dominates each of the two first coupled modes.The first coupled mode of variability between the SST and atmospheric pressure can be described as a strengthening and weakening of the cyclonic gyres, which seems to force fluctuations in a north–south dipole structure in the SST by Ekman upwelling which is a wind-related process. The atmospheric forcing of the SST changes is detectable in the sea with a lag of 1 and 6 months.
The goals of this work are to simulate the Bohai Sea circulation and thermohaline structure and to Investigate the physical mechanisms using the Coupled Hydrodynamical-Ecological Model for Regional and Shelf Seas (COHERENS) with realistic bottom topography and coastal geometry. The model-simulated seasonal variability of the circulation pattern and the thermal structure agree qualitatively with the observation. The salinity field is not as well simulated as the temperature. The thermohaline structure is vertically stratified during the summer monsoon. The sub-surface velocities are found to be compensating currents from the surface circulation. Several experiments are performed to identity the prevailing forcing functions and Bohai Sea characteristics: (1) control run, with all the surface forcing functions (thermohaline fluxes, wind, tides) present, (2) no-thermohaline flux run, (3) no-wind run, and (4) no-tide run. The experiments show that the surface wind effect is the major forcing to drive the surface currents and the thermohaline structure, the thermohaline flux is the important driving force for the thermal structure, and the tidal mixing is responsible for the deep layer characteristics. It is also found that a higher turbulence kinetic energy (TKE) is produced using the Mellor-Yamada turbulence closure scheme than the 'kappa-epsilon' scheme. The deeper regions present higher TKE at the surface than in shallow waters. Maximum TKE for July are greater than the maximum TKE in January.
"The hydrological regime of the gulf is such that evaporating surface water passes toward the coasts, sinks, and escapes from the gulf by counterflow at lower levels, the highest salinities, both of surface and bottom water, being in coastal areas. This regime, similar to that which must have existed in ancient evaporite basins, is used as a model by which to interpret probable circumstances of evaporite deposition. It is thence argued that in a marine basin in an arid region, introduction of a bar at the entry to the basin or simple overall shallowing without the introduction of a bar may produce similar results in respect to evaporite deposition and distribution. In either case higher grade evaporites will deposit in the more remote coastal areas of a basin contemporaneously with progressively lower grade evaporites toward the point of entry of 'freshening' oceanic water."
Salinity is an important component of the marine system. Previous studies indicated that the mean salinity in the Bohai Sea had increased by 2.0 psu in the second half of the 20th century, mainly due to a sharp decrease in the Yellow River runoff, and also the effects of large-scale climatic variations and the intrusions of the North Yellow Sea Water (NYSW). Since 2002, the Yellow River Conservancy Commission has carried out the flow regulation at the beginning of every flood season, resulting in more discharge of the Yellow River freshwater into the Bohai Sea. In this study, the variations of salinity in the Bohai Sea during the recent years are investigated using a well-established three-dimensional baroclinic model, HAMburg Shelf Ocean Model (HAMSOM). The simulation results show that the Yellow River diluted water was mainly discharged into the Laizhou Bay, so the remarkable increase in the Yellow River runoff after 2002 led to a regime shift of salinity in the Laizhou Bay. However, in other parts of the Bohai Sea, salinity variation was influenced by the surrounding rivers or the intrusions of NYSW, and has little relation with the Yellow River runoff. As a whole, advection is more important than diffusion in the salinity distribution, and seasonal oscillation is the main feature of salinity variation. Via several case studies, evaporation and precipitation rates are found to be important in the long-term simulation of salinity.
The hydrodynamical models of the Gulf developed at KFUPM Research Institute are briefly described. The models are used to compute the flows in the Gulf driven by density gradient using the two sets of data collected on Legs 1 and 6 of the Mt Mitchell cruise. The two flows are compared with one another, with the result of a similar computation using the 1977 Atlantis II data and with computations of the flow driven by the prevailing wind. The combined residual flow due to wind and density gradient is found and compared to empirical estimates of the residual flow derived from ship-drift reports. The accuracy of the models is tested using the computed and observed water velocities at some of the current meters deployed during the cruise.
The NOAA research vessel Mt Mitchell operated in the Gulf, Strait of Hormuz, and Gulf of Oman, from February to June 1992. Of seven separate legs, six official legs and on unofficial leg on the homeward journey, four were devoted primarily to physical oceanographic measurements. Basin-wide surveys of bottom sediments and biological variables were also undertaken but those results are not covered here. A variety of physical oceanographic observations were taken: 1. over 500 CTD casts were made; 2. seven current meter moorings were deployed and six were recovered yielding 11 quality current meter records at different depths; 3. 36 drifting buoys with Argos positioning were deployed; and 4. continuous shipboard measurements of meteorological and oceanographic variables were recorded. The expedition data base continues to grow as new data from coastal meteorological and tide stations are added. The measurements are reviewed from the experimental point of view. Data accuracy, resolution, and precision are discussed and quality assurance of the measurements is reviewed. The complete data set covers the important seasonal transition from mid-winter to early summer. During this period of time, solar heating created an intense thermocline which decoupled the surface mixed layer from the interior water. The data are reviewed in the light of prior measurements and recent modelling results.
Three turbulence closure schemes, designed for stratified shallow water flows, are presented. They are based upon κ-ε theory and use respectively two, one or zero transport equations for turbulent variables. The models are first tested on the evolution of a wind-driven turbulent layer in a stratified fluid. The results are at least qualitatively in agreement with observational and experimental data. A discussion is given about the existence of self-similar solutions. The models are compared next with the observational data of the Rhine outflow area. The periodic variation in the density structure, forced by wind and tides and which is clearly visible in the data, is predicted by the model. A physical interpretation of the model results is given in the absence of wind forcing. The effects of estuarine circulation, tidal straining and mixing on the development or breakdown of stratification are well represented by the model calculations.
A Module Representing Surface Fluxes of Momentum and Heat
- P J Luyten
- T De
- Mulder
P.J. Luyten, T. De Mulder, A Module Representing Surface Fluxes of Momentum and Heat, Technical Report No. 9, MAST-0050-C (MUMM), 1992, 30 pp.
COHERENS – A Coupled Hydrodynamical – Ecological Model for Regional and Shelf Seas: User Documentation
- P G Luyten
- J E Jones
- R Proctor
- A Tabor
- P Tett
- K Wil-Allen
Atmosphere – ocean dynamics, International geophysics series
- A E Gill