Seasonal variations of temperature and salinity in the Gulf of Elat (Aqaba) (original) (raw)
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Seasonal changes of tide signal(s), temperature, salinity and current were studied during the years 2004-2005 in the northernmost Gulf of Aqaba, which is under developmental activities, to obtain scientific bases for best management and sustainability. Spectrum analysis revealed permanent signals of tide measurements during all seasons, which represented semidiurnal and diurnal barotropic tides. The other signal periods of 8.13, 6.10-6.32, 4.16 and 1.02-1.05 h were not detected in all seasons, which were related to shallow water compound and overtides of principle solar and lunar constituents and to seiches generated in the Red Sea and the Gulf of Aqaba. Spatial and temporal distributions of temperature, salinity and density showed significant differences between months in the coastal and offshore region and no significant differences among the coastal sites, between the surface and bottom waters and between coastal and offshore waters. Therefore, the temporal and spatial variation of water properties in the northernmost Gulf of Aqaba behave similarly compared to other parts. The coastal current below 12 m depth was weak (3-6 cms-1) and fluctuated from east-northeastward to west-southwestward (parallel to the shoreline), which may be related to the effect of bottom topography and/or current density due to differential cooling between eastern and western parts in the study area, and wind-induced upwelling and downwelling in the eastern and western side, respectively. The prevailing northerly winds and stratification conditions during summer were the main causes of the southward current at 6 and 12 m depths with average speed of 28 and 12 cms-1 , respectively.
Oceanologia, 2006
Five years (1998,(2000)(2001)(2002)(2003) of summer records of temperature, nutrients and dissolved oxygen concentrations in the upper 400 m of the water column of the northern Gulf of Aqaba were employed to produce a simple statistical model of the relationship between temperature versus nitrate, phosphate, silicate and dissolved oxygen concentrations. Temperature profiles in the upper 400 m during summer revealed a clear thermocline in the upper 200 m. This was reflected in nutrient and oxygen concentrations as nitrate, phosphate, and silicate increased from the surface to deep water while dissolved oxygen decreased. The best fit relationship between temperature versus nitrate and phosphate was inverse linear and the best fit correlation between temperature versus silicate and dissolved oxygen was fractional. The observed nutrient concentrations were shaped by a combination of the hydrodynamics and biological factors. Deep winter mixing and high nutrient concentrations dominate during winter. Shortly after the water stratifies in spring, the nutrients are drawn down by phytoplankton during the spring bloom and remain low throughout the rest of the year. The regression equations presented here will be useful in estimating nutrient concentrations from temperature records as long as the annual natural cycle is the main driver of nutrient concentrations and
OCEANOLOGIA
Five years (1998,(2000)(2001)(2002)(2003) of summer records of temperature, nutrients and dissolved oxygen concentrations in the upper 400 m of the water column of the northern Gulf of Aqaba were employed to produce a simple statistical model of the relationship between temperature versus nitrate, phosphate, silicate and dissolved oxygen concentrations. Temperature profiles in the upper 400 m during summer revealed a clear thermocline in the upper 200 m. This was reflected in nutrient and oxygen concentrations as nitrate, phosphate, and silicate increased from the surface to deep water while dissolved oxygen decreased. The best fit relationship between temperature versus nitrate and phosphate was inverse linear and the best fit correlation between temperature versus silicate and dissolved oxygen was fractional. The observed nutrient concentrations were shaped by a combination of the hydrodynamics and biological factors. Deep winter mixing and high nutrient concentrations dominate during winter. Shortly after the water stratifies in spring, the nutrients are drawn down by phytoplankton during the spring bloom and remain low throughout the rest of the year. The regression equations presented here will be useful in estimating nutrient concentrations from temperature records as long as the annual natural cycle is the main driver of nutrient concentrations and
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The convectave/advectlve balance at the northern end of the Gulf of Elat was investigated by comparing observed data to a numerical model's predictions The data. monthly temperature and sahnlty profiles collected from July 1988 to August 1989, mdlcate a continuously developing annual cycle, with the water column reaching vemcal homogeneity in February and the new thermocllne beginning to develop m March In the summer, an upper 200 m thermally stratified layer (surface temperatures reaching 26°C) overlies a thermally homogeneous layer o! 21°C Sahmty is close to 40 5%0 and vanes by less than 0 5%0 throughout the year, although a sahmty minimum develops m the upper layer m late spring and erodes and deepens m the fall and winter as the water column becomes mixed
Journal of Marine Research, 1989
Annual budgets of salinity, total inorganic carbon, total alkalinity, nitrates, phosphates and silicates are estimated through the Strait of Bab-e\-Mandab. Two different methods that decouple the summer and winter periods are used. A direct method uses the concentrations of these parameters, the velocity of currents, and the area of a cro~s section in the strait. The calculations for the fluxes and budgets during the summer period were based on data collected during two cruises made in July and September 1982 (MEROU I and 2). An indirect method, based upon matrix inversion and the assumption of a steady-state balance of several properties over a period of one year, is used to calculate the winter and summer budgets of water, salinity, total inorganic carbon, total alkalinity, nitrates and phosphates. The summer budgets obtained by the two different methods are positive for all the properties-a gain for the Red Sea-and are of the same order of magnitude for both methods. For the winter period, budgets are positive for total inorganic carbon and total alkalinity and negative for salinity and nutrients. This gain of total inorganic carbon and total alkalinity through the Strait of Bab-el-Mandab can be quantitatively explained by exchanges of CO2 with the atmosphere and the processes of sedimentation in the basin.
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Observations from an eight-year ocean station at Chabahar showed that both salinity and electrical conductivity (EC) have increased over the past nine years. Meanwhile, pH remained at steady state levels and there was no significant trend in mean annual temperatures. The best repeating pattern of monthly oscillations was depicted in temperature data with the highest and the lowest temperatures occurring at 4th/ 5th and 10th/ 11th months, respectively. Changes in salinity/EC and temperature were moderately correlated. The mean monthly pH levels rarely fell below 8.00. There were no signs of hypoxia during the study period.