Temperature of seawater

Fig. 30.1. Volumes of minerals precipitated during a reaction model simulating the mixing at reservoir temperature of seawater into formation fluids from the Miller, Forties, and Amethyst oil fields in the North Sea. The reservoir temperatures and compositions of the formation fluids are given in Table 30.1. The initial extent of the system in each case is 1 kg of solvent water. Not shown for the Amethyst results are small volumes of strontianite, barite, and dolomite that form during mixing.

Fig. 5.3.7. Cn-LAS biodegradation in inoculated natural marine water at 5 and 25°C, representing the extreme temperatures of seawater in winter and summer time,... 

Since the mass ratio is multiplied by 1000, the units of salinity are parts per thousand, symbolized by %o. The average salinity of seawater is 35%o, which is eqifivalent to a 3.5% salt solution. As shown in Figure 3 3, 99% of the seawater in the ocean has a salinity between 33%o and 37%o. Note that the temperature of seawater is far more variable, ranging from -2° to 30°C with an average of 3 5°C. Fifty percent of the water has a salinity between 34.6%o and 34.8%o and a temperature between 1.3°C and 3.8°C. 

Below the thermocline, the temperature changes only little with depth. The temperature is a non-conservative property of seawater because adiabatic compression causes a slight increase in the in situ temperature measured at depth. For instance in the Mindanao Trench in the Pacific Ocean, the temperature at 8500 and 10,000 m is 2.23 and 2.48 °C, respectively. The term potential temperature is defined to be the temperature that the water parcel would have if raised adiabatically to the ocean surface. For the examples above, the potential temperatures are 1.22 and 1.16 °C, respectively. Potential temperature of seawater is a conservative index. 

The temperature of seawater is fixed at the sea surface by heat exchange with the atmosphere. The average incoming energy from the Sun at the Earth s surface is about four times higher at the equator than at the poles. The average infrared radiation heat loss... 

Fig. 4.60 (Song et al., 1996) shows the daily variation of O2 flux across the sea-air interface at the continuous stations 410 and 111. It can be seen that oxygen released to air was the main process in one day and night, and that the amount released in daytime was more than that at night. This was because photosynthesis produced more oxygen in daytime, and the high temperature of seawater also increased the release of oxygen. This feature was very obvious in Leg 9410. At station 410, the oxygen in air dissolved into seawater from 18 00 to 06 00, but it was O2 from seawater to air from 06 00 to 18 00. The oxygen released into air was —8.63 L/(m d) in Leg 9404. This reflected the fact that the seawater was supersaturated and the photosynthesis was very...

Assume the average thickness of air balloons is 3 = 1 m, the temperature of seawater at depth 10 m is 10°C. The heat flow from seawater to ice platform is... 

The temperature of seawater also varies with latitude from 30 C to —2 C at the surface, from the equator to the poles and with depth, although after a depth of 1000 m, the temperature of the ocean can be regarded as constant and equal to +2 C, regardless of geographical position (Peres, 1961 Peres and Deveze, 1963 Biju-Duval, 1994). 

The mass of 1.000 L of water at 4 °C is 1.000 kg. The density of water at 4 °C is 1000 g/1000 mL, or 1.000 g/mL. At 20 °C, the density of water is 0.9982 g/mL. Density is a function of temperature because volume varies with temperature, whereas mass remains constant. One reason that climate change is a concern is because as the average temperature of seawater increases, the seawater will become less dense, its volume will increase, and sea level will rise—even if no continental ice melts. 

In a similar vein, mean seawater temperatures can be estimated from the ratio of 0 to 0 in limestone. The latter rock is composed of calcium carbonate, laid down from shells of countless small sea creatures as they die and fall to the bottom of the ocean. The ratio of the oxygen isotopes locked up as carbon dioxide varies with the temperature of sea water. Any organisms building shells will fix the ratio in the calcium carbonate of their shells. As the limestone deposits form, the layers represent a chronological description of the mean sea temperature. To assess mean sea temperatures from thousands or millions of years ago, it is necessary only to measure accurately the ratio and use a precalibrated graph that relates temperatures to isotope ratios in sea water. 

The iaterrelatioaship of nonalkaline scales (CaSO, CaSO /2H2O, CaSO 2H20) depeads oa temperature and the concentration of CaSO. To assure that no hemihydrate scale forms, MSF operators must mn their plants ia such a manner as to assure that the coaceatratioa of the total dissolved sohds does aot exceed 70,000 ppm at temperatures of 120°C. With average-salinity seawater, plants can operate at a concentration factor of 2, but in the Middle East where water salinity can be as high as 50,000 ppm, the concentration factor should not exceed 1.4. Under no circumstances should the total dissolved soHds exceed 70,000 ppm, ie, twice the concentration of normal seawater at 120°C. 

Although desalination technologies ate diverse, MSF has been for some time, and will remain well into the next century, the main process for desalination of seawater. Inroads ate being made by the multi-effect processes and, in particular, by the low temperature ME processes. 

Figure 1 The solubility of the prineipal atmospherie gases in seawater, as a funetion of temperature. Units are millilitres of gas eontained in a litre of seawater of salinity 35 psu, assuming an overlying atmosphere purely of eaeh gas. Note that salinity is defined in terms of a eonduetivity ratio of seawater to a standard KCl solution and so is dimensionless. The term praetieal salinity unit , or psu, is often used to define salinity values, however. It is numerieally praetieally identieal to the old style unit of parts per thousand by weight...

The minimum work needed is equal to the difference in free energy between the incoming feed (i.e. seawater or brackish water) and outgoing streams (i.e. product water and discharge brine). For the normal seawater (3.45 per cent salt) at a temperature of 25° C, for usual recoveries the minimum work has been calculated as equal to about 0.86 kWh/m Table 5 makes the desired comparison. 

Design a seawater cooler to cool the total stream from the example f ield in its later stages of life from a flowing temperature of 175 F to a temperature of 100°F to allow further treating. 

Variability of Seawater Vertical sections through seawater showing the distribution of temperature, salinity, and oxygen for the Pacific Ocean and Western Atlantic Ocean are shown in Figures 21.3 and 21.4. The global variability of natural seawater and its effects on corrosion have been reviewed in particular with respect to seasonal variation of temperature, salinity, oxygen and pH in the Pacific surface water. Data is also given on... 

The freezing point, temperature of maximum density, osmotic pressure and specific heat for seawater of various salinities are given in Table 21.23. 

HSI anodes are subject to severe pitting by halide ions and this precludes their use in seawater or other environments in which these ions may be present in quantity. They are ideal for fresh-water applications (below 2(X)p.p.m. Cl"), although not for temperatures above 38°C. The addition of Mo or Cr to the alloy can improve performance under these conditions, with an upper limit of temperature of which may be affected by the... 

The density of seawater is controlled by its salt content or salinity and its temperature. Salinity is historically defined as the total salt content of seawater and the units were given as grams of salt per kilogram of seawater or parts per thousand (%o). Salinity was expressed on a mass of seawater basis because mass, rather than volume, is conserved as temperature and... 

Because seawater signatures of temperature and salinity are acquired by processes occurring at the air-sea interface we can also state that the density characteristics of a parcel of seawater are determined when it is at the sea surface. This density signature is locked into the water when it sinks. The density will be modified by mixing with other parcels of water but if the density signatures of all the end member water masses are known, this mixing can be unraveled and the proportions of the different source waters to a given parcel can be determined. 

Low-temperature circulation of seawater through mid-ocean ridge systems creates a deficiency in Mg and an excess in Ca at middepths (de Villiers and Nelson, 1999). 

Fig. 11-7 Distribution of dissolved carbon species in seawater as a function of pH. Average oceanic pH is about 8.2. The distribution is calculated for a temperature of 15°C and a salinity of 35%o. The equilibrium constants are from Mehrbach et al. (1973).

The putative feedback involves the influence of emissions of this aerosolgenic gas, (CH3)2S, that influences cloud albedo and hence either the temperature of the seawater in which the phytoplankton live or the amount of light available for their photosynthesis. Figure 17-9 represents the hypothetical feedback loop, and emphasizes that even the sign of the feedback is not known. Contradictory evidence has been developed... 

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