Physical properties of sea water

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Welcome to our presentation TOPICS ON Mixing process of sea waterE.MAIL- magidurdu@yahoo.com

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SUBMITTEDBY KHALEDA NASRIN SHARMISTA SARKAR SHARMIN AKTER E.MAIL- magidurdu@yahoo.com

Mixing process of sea waterMix means combine or put together (two or more substances or things) so that the constituents of each are diffused among those of the other.Water is a common chemical substance that is essential to all known forms of life.[1] In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapor. About 1,460 teratonnes (Tt) of water covers 71% of the Earth's surface, mostly in oceans and other large water bodies, with 1.6% of water below ground in aquifers and 0.001% in the air as vapor, clouds (formed of solid and liquid water particles suspended in air), and precipitation.[2] Some of the Earth's water is contained within man-made and natural objects near the Earth's surface such as water towers, animal and plant bodies, manufactured products, and food stores.So mixing process of water is a process by water of a specific place mixes with the water of another place with vital velocity : 

Mixing process of sea waterMix means combine or put together (two or more substances or things) so that the constituents of each are diffused among those of the other.Water is a common chemical substance that is essential to all known forms of life.[1] In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapor. About 1,460 teratonnes (Tt) of water covers 71% of the Earth's surface, mostly in oceans and other large water bodies, with 1.6% of water below ground in aquifers and 0.001% in the air as vapor, clouds (formed of solid and liquid water particles suspended in air), and precipitation.[2] Some of the Earth's water is contained within man-made and natural objects near the Earth's surface such as water towers, animal and plant bodies, manufactured products, and food stores.So mixing process of water is a process by water of a specific place mixes with the water of another place with vital velocity Mixing process of sea water include; ?wave ?tides ?cuurents

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Fig.model of hydrogen bonds between molecules of water

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The properties of sea water are a function of Temperature salinity pressure. Temperature Definition. Temperature is a thermodynamic property of a fluid, and is due to the activity of molecules and atoms in the fluid. The more the activity (energy), the higher the temperature. Temperature is a measure of the heat content. Heat and temperature are related through the specific heat: (equation in class). When the heat content is zero (no activity), the temperature is absolute zero (on the Kelvin scale). Heat Heat per unit volume is computed from temperature using Q = density*specific heat*T where Q is heat/volume and T is temperature in degrees Kelvin.

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Potential temperature Definition. "Potential temperature" is the temperature which a water parcel has when moved adiabatically to another pressure. In the ocean, we commonly use the sea surface as our "reference" pressure for potential temperature - we compare the temperatures of parcels as if they have been moved, without mixing or diffusion, to the sea surface. Since pressure is lowest at the sea surface, potential temperature (computed at surface pressure) is ALWAYS lower than the actual temperature unless the water is lying at the sea surface. Salinity Definition. Salinity is roughly the number of grams of dissolved matter per kilogram of seawater. This was the original definition, and at one time salinity was determined by evaporating the water and weighing the residual. The dissolved matter in seawater affects its density (see section 5 below), hence the importance of measuring salinity. Conductivity Definition. Conductivity of sea water depends strongly on temperature, somewhat less strongly on salinity, and very weakly on pressure. If the temperature is measured, then conductivity can be used to determine the salinity. Salinity as computed through conductivity appears to be more closely related to the actual dissolved constituents than is chlorinity, and more independent of salt composition. Therefore temperature must be measured at the same time as conductivity, to remove the temperature effect and obtain salinity. Accuracy of salinity determined from conductivity: 0.001 to 0.004.

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Density Definition. Seawater density depends on temperature, salinity and pressure. Colder water is denser. Saltier water is denser. High pressure increases density. The dependence is nonlinear. An empirical equation of state is used, based on very careful laboratory measurements. Sea ice The freezing point of seawater is lower than that of freshwater. As sea water freezes, it forms pockets of salt. The salt (brine) leaches out of the bottom of the ice and the brine drips into the water below the ice. Thus sea ice when melted is considerably fresher than the original water which was frozen. The "brine rejection" process creates dense water below the sea ice formation area. This can be an important contributor to dense water formation in a global sense as the densest waters are formed at high latitudes, and often involve sea ice. The faster that sea ice is frozen, the less likely that the salt can escape. Thus the saltiest sea ice is formed at the lowest temperatures. Sverdrup et al. (1942 text) tabulate the salinity of ice formed from water which starts at salinity 30. When frozen at an air temperature of -16C, the salinity of the ice is 5.6. When frozen at an air temperature of -40C, the salinity of the ice is 10.2.

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Oxygen Non-conservative tracer. Source is primarily air-sea interaction, some subsurface source in outgassing by plankton. Oxygen is consumed in situ. Oxygen content decreases with age, so it can be used in a rough way to date the water. It is not a good age tracer because the consumption rate is not a constant. Since waters of different oxygen content mix, the age is not simply related to content. Per cent saturation of oxygen depends strongly on temperature (show figure). Cold water holds more oxygen. Thus the per cent saturation (or related quantity "Apparent oxygen utilization" is a better tracer than oxygen content itself. Nitrate and phosphate Also non-conservative. Nitrate and phosphate are completely depleted in surface waters in the subtropical regions where there is net downwelling from the surface and hence no subsurface source of nutrients. In upwelling regions there is measurable nitrate/phosphate in the surface waters due to the subsurface source (figure from Hayward and McGowan; other figures based on woce data). Nitrogen is present in sea water in dissolved N2 gas, nitrite, ammonia, and nitrate, as well as in organic forms. As water leaves the sea surface, particularly the euphotic zone, productivity is limited by sunlight and nutrients are "regenerated". That is, the marine snow is decomposed by bacteria and produces nitrate and phosphate. Nitrate and phosphate thus increase with the age of the water. Vertical sections and maps of nitrate and phosphate appear nearly as mirror images of oxygen, but there are important differences in their patterns, particularly in the upper 1000 meters; vertical extrema are not always co-located and sometime large multiple extrema appear on one parameter and not in the others

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Dissolved silica non-conservative. In seawater it is present as H2SiO4 (silicic acid) rather than silicate (SiO3), but many people use the term silicate. This nutrient is also depleted in surface waters similarly to nitrate and phosphate - completely depleted in downwelling areas and small but measurable quantities in upwelling areas. Subsurface distributions of silica look something like nitrate and phosphate and mirror oxygen since silica is also regenerated in situ below the euphotic zone. However, silica in marine organisms is associated with skeletons rather than fleshy parts and so dissolves more slowly in the water. Much of the silica thus falls to the bottom of the ocean and accumulates in the sediments (map of types of sediments). Dissolution from the bottom sediments constitutes a source of silica for the water column which is not available for nitrate, phosphate or oxygen. Another independent source of silica are the hydrothermal vents which spew water of extremely high temperature, silica content, and helium content, as well as many other minerals, into the ocean. The three named quantities are used commonly to trace hydrothermal water. Transient tracers Other tracers used commonly for ventilation and deep water circulation include chlorofluorocarbons, tritium, helium-3 and carbon-14. CFC's and tritium are strictly anthropogenic. Their source functions have been well described and they are used to trace recently ventilated waters into the ocean, and various combinations of CFC's, tritium/helium3 are used to attach ages to water parcels, although not without approximation.

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NEW PHYSICAL FACTORS oxygen/ CO2 oxygen is exchanged only in one place, through the ocean's surface, and CO2 goes this way too. In the shallow zone, where sunlight reaches deep enough, and only where there are enough nutrients, will oxygen be produced and carbondioxide used. At night, and in the deep ocean, the process reverses, leading to a shortage in oxygen at the deep sea bed. stratification due to the combined effects of salinity and temperature, many places in the sea are stratified (layered), blocking the convection of water (up/down movement) and gases. It may lead to severe shortage of oxygen. salinity the sea water is saltier than the body tissues of many marine organisms, and they lose moisture continually by osmosis. A fish must drink seawater in order to maintain a balance of body salts. currents winds on land are not exactly like currents, but both transport heat. The heat transport of currents is often underestimated because they flow slowly (current=0.5km/h; wind=35km/h). However, the heat capacity of 100m of water column (depth), is enormous. At the surface, winds and currents exchange heat, resulting in a major influence on climate and season.

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Fig.Salinity Seawater composition (by mass)

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wave action whereas winds blow mainly in one direction, waves swing to and fro. In the shallows, they are very destructive, also because water is 800 times heavier than air. This has had a major effect on the shape and development of seaweeds. Wave action is also important fore mixing nutrients and exchanging gases. tides the moon and sun tides are felt in the sea as a predictable rise and fall in sea level, accompanied by currents. Such tidal currents cause extensive mixing and distribution of pollutants and plankton in coastal waters. In the open ocean, tides are not noticeable. substrate on the move everything on land has a fixed place. Plants are well rooted. In the sea only the rock surface provides reliable holdfast. Planktonic organisms are constantly on the move. The sandy and muddy seabeds are stirred regularly, forcing organisms living there, to rebuild their warrens and to dig deeper.

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substrate as attachment because plants are surrounded by nutrients and water, they do not need roots and soil. They attach to the rocks and absorb moisture and nutrients direct through their entire surfaces. Other organisms can attach themselves likewise, because the food comes towards them by movement of the currents. decreasing light intensity unlike on land, light intensity decreases rapidly depth. In the with coastal zone, plant life stops at 20-30m depth. The quality of the light changes too, becoming more blue. The light intensity and quality gradient gives rise to biodiversity and horizontally zoned habitats

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WAVES, CURRENTS, TIDES Waves Waves transfer energy from one place to another. Waves in the oceans (or large lakes) are caused by wind blowing over the surface of the water. All waves have certain characteristics in common. The highest point of a wave is called the crest. The lowest point of a wave is called the trough. Wavelength is the horizontal distance between two adjacent wave crests. Wave height - the vertical distance from the bottom of a trough to the top of a crest The number of waves that pass a given point in one second is the wave's frequency.

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Fig.Diagram illustrating the parts of a wave

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CURRENTS Currents are the horizontal, unidirectional flow of water. Ocean currents influence the weather in coastal areas. In order to map and predict currents,scientists release floating buoys and track their positions. The horizontal movement of water is caused by a number factors. These include: Wind moving over the water. Currents are caused by friction between the wind and the surface of the water. Most currents in the upper kilometer of the ocean are driven by the wind. They are called surface currents. Wind-driven currents affect about 20% of the ocean, by volume. These are the currents that most people know about. The sun is the source of winds in the atmosphere and currents in the ocean. Once the surface currents are set in motion by the wind, they are influenced by the and horizontal pressure gradients Differences in salinity Salinity differences cause thermohaline circulation or vertical movements of ocean water masses because of density differences that are controlled by variations in temperature and salinty. Differences in water temperatures caused by uneven heating of the Earth's atmosphere by the Sun. Cold water is more dense than warm water, and as a result, tends to sink to the ocean bottoms and spread. Cold water originates at high latitudes where cold winds blow across the water, and cool and evaporate it. If the temperatures are low enough, sea ice will form, which is made of fresher water than sea water. Salts are left behind in the sea water when sea ice forms. The cold, salty water becomes more dense and sinks deep into the ocean. Note that cold water can hold more oxygen than warmer

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FIG.THE WATER PARTICLE MOVES IN A VERTICAL CIRCLE

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FIG.THE ELEMENTS OF A RIP CURRENT

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Tides There is a vertical rise and fall in sea level of approximately a meter or more, once or twice per day. Cause of tides? The Moon's gravitational pull, and to a lesser extent, the Sun's gravitational pull. But gravity is only one of the major forces responsible for creating tides. Another is inertia, which is the force that acts to counterbalance gravity. It is the tendency of moving objects to continue moving in a straight line. Together, gravity and inertia are responsible for the creating the two major tidal bulges on the Earth. Tidal Cycle A high and low tide that occur in succession. Semi-diurnal Tide: The most common tidal pattern, featuring two high tides and two low tides each day. Successive high or low tides are approximately the same height. Diurnal Tide: There is only one high tide and one low tide during each day. Successive high and low tides are approximately the same height. Diurnal tides occur in the Gulf of Mexico. Mixed Tide: Wide variation in heights of successive high and low waters, and longer tide cycles than those of the semidiurnal cycle. Tidal Range The vertical difference in water level between the high tide and low tide, during one tidal cycle.

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Fig. Spring tides occur during the full moon and the new moon.

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What Causes Tides?"There are several kinds of tides. The ones that break upon a beach every 10 seconds to a minute are caused by sea level disturbances out in the ocean produced by such things as storms. Also, the various circulation currents of sea water can have velocity components directed towards the land which will bring water up onto the beach. As this water travels towards the beach from deep water to shallow water, its amplitude will increase until it finally 'breaks' as a full-fledged breaker, suitable for surfing etc. Now, underlying this minute to minute activity is a slower water wave which causes an alternating pattern of high-tide, low-tide, high-tide, low-tide in most places on the Earth that are directly on the ocean. This roughly 6 hour cycle is caused by the gravitational tugging of the Moon upon the Earth. This 'tidal' pull causes the shape of the solid Earth to be not perfectly round by something like a few dozen yards over its entire 27,000 mile circumference. The Earth gets distorted a small bit, but because it is solid rock its a small effect. The water in the oceans, however, gets distorted into a roughly ellipsoidal ( football-like) shape with a much larger amplitude. The orientation of this shape changes from minute to minute as the Moon orbits the Earth, which is why the high and low tide times change all the time. The Moon causes these tides by deforming the oceans, and as the Earth rotates under this ocean bulge, it causes a high tide to propagate onto beaches. Because there are two bulges, we get two high tides, and also two low tides each day. The Sun also causes tides on the Earth because even though it is so far away, it is very massive. These solar tides are about half as strong as the ones produced by the Moon, and they cause the so-called Spring tides and the Neap Tides. When the bulge of ocean water raised by the Moon is added the a similar tidal bulge raised by the Sun, you get a higher, high tide called the Spring Tide. When the solar low tide is added to the lunar low tide, you get the Neap Tide.

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When the Earth, Moon and Sun are aligned for Spring Tides, are they highest at Full or New Moon? "Spring tides are about the same height whether at New or Full Moon, because the tidal bulge occurs on both sides of the Earth...the side toward the Moon ( or sun) and the side away from the Moon (or Sun). They will not be equally high because the distance between the Earth and Sun, and the Earth and Moon both vary and so will their tide producing effectiveness. The highest Spring tides occur when the Moon is at its closest to the Earth...the so-called P Effects on life

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Aquatic life forms Earth's waters are filled with life. The earliest life forms appeared in water; nearly all fish live exclusively in water, and there are many types of marine mammals, such as dolphins and whales that also live in the water. Some kinds of animals, such as amphibians, spend portions of their lives in water and portions on land. Plants such as kelp and algae grow in the water and are the basis for some underwater ecosystems. Plankton is generally the foundation of the ocean food chain. Different water creatures have found different solutions to obtaining oxygen in the water. Fish have gills instead of lungs, though some species of fish, such as the lungfish, have both. Marine mammals, such as dolphins, whales, otters, and seals need to surface periodically to breathe air. Effects on human civilization Water Fountain Civilization has historically flourished around rivers and major waterways; Mesopotamia, the so-called cradle of civilization, was situated between the major rivers Tigris and Euphrates; the ancient society of the Egyptians depended entirely upon the Nile. Large metropolises like Rotterdam, London, Montreal, Paris, New York City, Shanghai, Tokyo, Chicago, and Hong Kong owe their success in part to their easy accessibility via water and the resultant expansion of trade. Islands with safe water ports, like Singapore, have flourished for the same reason. In places such as North Africa and the Middle East, where water is more scarce, access to clean drinking water was and is a major factor in human development. Health and pollution Water fit for human consumption is called drinking water or potable water. Water that is not potable can be made potable by distillation (heating it until it becomes water vapor, and then capturing the vapor without any of the impurities it leaves behind), or by other methods (chemical or heat treatment that kills bacteria). This natural resource is becoming scarcer in certain places, and its availability is a major social and economic concern. Currently,

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Human uses Agriculture As a scientific standard a highly stable temperature point—the scientists chose to redefine the standard and to perform their measurements at the most stable density point: the temperature at which water reaches maximum density, which was measured at the time as 4 °C.[13] The Kelvin temperature scale of the SI system is based on the triple point of water. The scale is a more accurate development of the Celsius temperature scale, which is defined by the boiling point (100 °C) and melting point (0 °C) of water. For drinking The human body is anywhere from 55% to 78% water depending on body size.[14] To function properly, the body requires between one and seven liters of water per day to avoid dehydration; the precise amount depends on the level of activity, temperature, humidity, and other factors. Most of this is ingested through foods or beverages other than drinking straight water. in general recommended (including food sources): 2.7 liters of water total for women and 3.7 liters for menWater is excreted from the body in multiple forms; through urine and feces, through sweating, and by exhalation of water vapor in the breath. With physical exertion and heat exposure, water loss will increase and daily fluid needs may increase as well. Humans require water that does not contain too many impurities. Common impurities include metal salts and/or harmful bacteria, such as Vibrio. Some solutes are acceptable and even desirable for taste enhancement and to provide needed electrolytes. The single largest freshwater resource suitable for drinking is Lake Baikal in Siberia, which has a very low salt and calcium content and is very clean.

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As a dissolving agent or solvent Dissolving (or suspending) is used to wash everyday items such as the human body, clothes, floors, cars, food, and pets. Also, human wastes are carried by water in the sewage system. Its use as a cleaning solvent consumes most of water in industrialized countries. As a heat transfer fluid ice used for cooling Water and steam are commonly used as heat transfer fluids in diverse heat exchanger systems, because of the availability and high heat capacity, both as a coolant and for heating slows the nuclear reaction down. Extinguishing fires water is necessary for wildfires fire fighting and other fire fighting Water has a high heat of vaporization and is relatively inert, which makes it a good fire extinguishing fluid. The evaporation of water carries heat away from the fire. E.MAIL- magidurdu@yahoo.com

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THANKS TO ALL