Relative Weight
It is interesting to note that 1liter of air weighs .013N and 1liter of water weighs 10N, that is 770 times heavier than air. The relative weight of seawater depends on the density and temperature of the water. Density itself, though insignificantly, depends on temperature. That is why at 20ºC the density of the water is lower by .2% than it is at 4ºC. Pure distilled water has a relative weight of 1 at a temperature of 4ºC, that is, 1 cm3 of water weighs 1g. Seawater is heavier than fresh water by 2.5–3% because of the greater amount of salts dissolved in it; its relative weight is 1.025. It may be concluded that a diver weighs less in seawater than in fresh water. Relative weight is important for determining buoyancy.
It is interesting to note that 1liter of air weighs .013N and 1liter of water weighs 10N, that is 770 times heavier than air. The relative weight of seawater depends on the density and temperature of the water. Density itself, though insignificantly, depends on temperature. That is why at 20ºC the density of the water is lower by .2% than it is at 4ºC. Pure distilled water has a relative weight of 1 at a temperature of 4ºC, that is, 1 cm3 of water weighs 1g. Seawater is heavier than fresh water by 2.5–3% because of the greater amount of salts dissolved in it; its relative weight is 1.025. It may be concluded that a diver weighs less in seawater than in fresh water. Relative weight is important for determining buoyancy.
Resistance
Just like any other liquid, water practically does not shrink. That is why its density almost does not change at different depths. At a pressure of 500at water shrinks by 1/47,000,000 of its volume. If it did not shrink at all, however, the sea level would rise by 30m. Water resistance is greatest in the surface layer. Therefore, less effort is needed for swimming in that layer.
Transparency The relative transparency of seawater is determined by the average depth, at which a white disc of a 30cm diameter is no longer seen. Greatest transparency has the Sargatian Sea (66.5m), second greatest transparency have the Syrian coasts of the Mediterranean Sea. Least transparent is the North Sea (the British Channel) – some 6.5–12m.
The heat capacity of seawater is 3134 times greater than that of air. Water has insignificant heat conductivity. That is why distribution of heat to greater depths is very slow and is mainly achieved through convection.
The highest temperature of water is registered to occur between 3 and 4 p.m., and the lowest – a couple of hours after sunrise. There are three temperature layers of seawater: surface layer (epilymnion), intermediate layer (metalymnion), and deepest layer (hypolymnion). The thickness of the former two layers varies with the weather, season, and currents. The temperature of the surface layer is almost constant, being between 19 and 25ºC in the summer. As the deepest layer begins, temperature drops by a few more degrees and it remains constant thereafter (7–9ºC). That is the temperature of sea depths and it does not depend on the season.
Transparency The relative transparency of seawater is determined by the average depth, at which a white disc of a 30cm diameter is no longer seen. Greatest transparency has the Sargatian Sea (66.5m), second greatest transparency have the Syrian coasts of the Mediterranean Sea. Least transparent is the North Sea (the British Channel) – some 6.5–12m.
The heat capacity of seawater is 3134 times greater than that of air. Water has insignificant heat conductivity. That is why distribution of heat to greater depths is very slow and is mainly achieved through convection.
The highest temperature of water is registered to occur between 3 and 4 p.m., and the lowest – a couple of hours after sunrise. There are three temperature layers of seawater: surface layer (epilymnion), intermediate layer (metalymnion), and deepest layer (hypolymnion). The thickness of the former two layers varies with the weather, season, and currents. The temperature of the surface layer is almost constant, being between 19 and 25ºC in the summer. As the deepest layer begins, temperature drops by a few more degrees and it remains constant thereafter (7–9ºC). That is the temperature of sea depths and it does not depend on the season.
Water Motion
Water motion constitutes sea currents and waves. The reason for the formation of currents might be the different density of water, constant winds, etc. Ocean currents are usually caused by constant winds, whereas local ones are mainly due to the character of coastlines. According to he direction of their flow, currents can be classified as vertical or horizontal. There are three main types of waves: wind waves, standing waves, and seismic waves.
Wind
is the main reason for the formation of waves. The process of wave formation can be divide into different stages. When the speed of wind is less than 1m/s, air motion does not affect the surface of the water. If wind intensifies, these rows of waves become irregular and peaks appear, which are due to the different pressure at the front and at the back of the wave. At a greater speed of wind large waves are formed, running in parallel rows. Th largest waves reaching hundreds of meters continue even when the wind has ceased. They create the so-called dead drift.
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