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Salinity is defined as the ratio between the weight of the dissolved materials and the weight of the sample sea water. Generally, salinity is defined as ‘the total amount of solid material in grams contained in one kilogram of sea water and is expressed as part per thousand (%o) e.g., 30%o (means 30 grams of salt in 1000 grams of sea water).
The oceanic salinity not only affects the Marine Organisms and plant community but it also affects the physical properties of the Oceans such as temperature, density, pressure, waves and currents etc. The freezing point of ocean water also depends on salinity e.g., more saline water freezes slowly in comparison to less saline water.
Controlling Factors of Salinity
There is a wide range of variation in the spatial distribution of salinity within the oceans and the seas. The factors affecting the amount of salt in different oceans and seas are called as controlling factors of oceanic salinity.
There is direct positive relationship between the rate of evaporation and salinity e.g., greater the evaporation, higher the salinity and vice versa. In fact, salt concentration increases with rapid rate of evaporation. Evaporation due to high temperature with low humidity (dry condition) causes more concentration of salt and overall salinity becomes higher. For example, salinity is higher near the tropics than at the equator because both the areas record high rate of evaporation but with dry air over the tropics of Cancer and Capricorn.
Precipitation is inversely related to salinity e.g., higher the precipitation, lower the salinity and vice versa. This is why the regions of high rainfall (equatorial zone) record comparatively lower salinity than the regions of low rainfall (sub-tropical high pressure belts).
The extra water in the temperate regions supplied by melt-water of ice coming from the polar areas increases the volume of water and therefore reduces salinity. It may be simply stated that the volume of water in the oceans is increased due to heavy rainfall and thus the ratio of salt to the total volume of water is reduced.
Influx of river water
Though the rivers bring salt from the land to the oceans but big and voluminous rivers pour down immense volume of water into the oceans and thus salinity is reduced at their mouths. For example, comparatively low salinity is found near the mouths of the Ganga, the Congo, the Nizer, the Amazon, the St. Lawrence etc.
The effect of influx of river water is more pronounced in the enclosed seas e.g. the Danube, the Dneister, the Dneiper etc. reduce the salinity in the Black Sea (180/00). Salinity is reduced to 50/00 in the Gulf of Bothnia due to influx of immense volume of water brought by the rivers. On the other hand, where evaporation exceeds the influx of fresh river waters, there is increase in salinity (Mediterranean Sea records 400/00).
Atmospheric Pressure and wind direction
Anticyclonic conditions with stable air and high temperature increase salinity of the surface water of the oceans. Sub-tropical high pressure belts represent such conditions to cause high salinity. Winds also help in the redistribution of salt in the oceans and the seas as winds drive away saline water to less saline areas resulting into decrease of salinity in the former and increase in the latter.
Circulation of oceanic water
Ocean currents affect the spatial distribution of salinity by mixing seawaters. Equatorial warm currents drive away salts from the western coastal areas of the continents and accumulate them along the eastern coastal areas. The high salinity of the Mexican Gulf is partly due to this factor. The North Atlantic Drift, the extension of the Gulf Stream increases salinity along the north-western coasts of Europe. Similarly, salinity is reduced along the north-eastern coasts of N. America due to cool Labrador Current.
Distribution of Salinity
The Average salinity in the oceans and the seas is 35%o but it spatially and temporally varies in different oceans, seas, and lakes. The variation in salinity is both horizontal and vertical (with depth). Salinity also varies from enclosed seas through partially closed seas to open seas.
Horizontal Distribution: Horizontal distribution of oceanic salinity is studied in relation to latitudes but regional distribution is also considered wherein each ocean is separately described. Similarly, the pattern of spatial distribution of salinity in enclosed seas, partially enclosed seas and open seas is also considered.
On an average, salinity decreases from equator towards the poles. It may be mentioned that the highest salinity is seldom recorded near the equator though this zone records high temperature and evaporation but high rainfall reduces the relative proportion of salt. Thus, the equator accounts for only 350/00 salinity.
The highest salinity is observed between 200-400N (360/00) because this zone is characterized by hi0gh temperature, high evaporation but significantly low rainfall. The average salinity of 350/00 is recorded between 100-300 latitudes in the southern hemisphere. The zone between 400-600 latitudes in both the hemispheres records low salinity where it is 310/00 and 330/00 in the northern and the southern hemispheres respectively.
Salinity further decreases in the polar zones because of influx of melt-water. On an average, the northern and the southern hemispheres record average salinity of 340/00 and 350/00 respectively.
Vertical Distribution
No definite trend of distribution of salinity with depth can be spelt out because both the trends of increase and decrease of salinity with increasing depths have been observed. For example, salinity at the southern boundary of the Atlantic is 330/00 at the surface but it increases to 34.50/00 at the depth of 200 fathoms (1200 feet).
It further increases to 34.75% at the depth of 600 fathoms. On the other hand, surface salinity is 370/00 at 20°S latitude but it decreases to 350/00 at greater depth.
The following characteristics of vertical distribution of salinity may be stated:
- Salinity increases with increasing depth in high latitudes i.e. there is positive relationship between the amount of salinity and depth because of denser water below.
- The trend of increase of salinity with increasing depths is confined to 200 fathoms from the surface in middle latitudes beyond which it decreases with increasing depths. Salinity is low at the surface at the equator due to high rainfall and transfer of water through equatorial currents but higher salinity is noted below the water surface. It again becomes low at the bottom. More studies and data of salinity distribution at regular depths in different oceans and seas are required so that definite characteristic features of vertical distribution of salinity may be determined.
- Maximum salinity is found in the upper layer of the oceanic water. Salinity decreases with increasing depth. Thus, the upper zone of maximum salinity and the lower zone of minimum salinity is separated by a transition zone which is called as thermocline zone, on an average above which high salinity is found while low salinity is found below this zone. It may be remembered that this should not be taken as a general rule because the vertical distribution of salinity is very complicated.
- It may be mentioned that the depth zone of oceans between 300m and 1000m is characterized by varying trends of vertical Distribution of Temperature, density of seawater, and salinity of ocean water.
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Salinity is the saltiness or dissolved salt content of a body of water. It is usually measured in parts per thousand (ppt), or grams of salt per kilogram of water. The average salinity of the ocean is about 35 ppt, but it can vary depending on location and time of year.
The main cause of ocean salinity is the evaporation of seawater. When water evaporates, it leaves behind the salt and other Minerals that were dissolved in it. This is why the ocean is saltier than freshwater lakes and rivers.
Other factors that can affect ocean salinity include precipitation, river runoff, and melting Glaciers. Precipitation adds freshwater to the ocean, which lowers the salinity. River runoff also adds freshwater to the ocean, but it can also add minerals, which can increase the salinity. Melting glaciers add freshwater to the ocean, but they also add salt, which can increase the salinity.
Ocean salinity has a number of effects on the marine Environment. It affects the density of seawater, which in turn affects the circulation of water in the ocean. Salinity also affects the Growth of phytoplankton, which are the base of the marine food web.
Ocean salinity is measured using a variety of methods, including the conductivity method, the titration method, and the freezing point depression method. The conductivity method is the most common method, and it measures the electrical conductivity of seawater. The titration method measures the amount of silver nitrate that is needed to precipitate out all of the chloride ions in a sample of seawater. The freezing point depression method measures the freezing point of seawater, which is lower than the freezing point of pure water.
Ocean salinity is an important factor in Climate change. As the Earth’s climate changes, the salinity of the ocean is also changing. This is because changes in temperature and precipitation can affect the amount of evaporation and precipitation that occurs. Changes in salinity can have a number of effects on the marine environment, including changes in the distribution of marine life and changes in the rate of sea level rise.
Ocean salinity is also important for human Health. The salinity of seawater can affect the taste of drinking water, and it can also affect the absorption of nutrients from food. In some cases, high salinity can even lead to dehydration.
The future of ocean salinity is uncertain. As the Earth’s climate continues to change, the salinity of the ocean is likely to change as well. This could have a number of negative effects on the marine environment and on human health. It is important to monitor ocean salinity and to understand its effects so that we can take steps to mitigate the negative effects of Climate Change.
In addition to the effects mentioned above, ocean salinity can also affect the following:
- The growth of coral reefs: Coral reefs are sensitive to changes in salinity, and even small changes can cause them to die.
- The distribution of fish populations: Fish are adapted to live in certain salinity ranges, and changes in salinity can force them to move to new areas.
- The productivity of Fisheries-2/”>Fisheries: Fisheries rely on a healthy marine environment, and changes in salinity can reduce the productivity of fisheries.
- The transport of pollutants: Pollutants can be transported by ocean currents, and changes in salinity can affect the way that pollutants are transported.
- The stability of sea ice: Sea ice is sensitive to changes in salinity, and changes in salinity can affect the extent of sea ice.
Ocean salinity is a complex issue with a number of important implications. It is important to understand the causes and effects of ocean salinity so that we can take steps to mitigate the negative effects of climate change.
What is the pH of the ocean?
The pH of the ocean is about 8.1, which is slightly alkaline.
What is the average salinity of the ocean?
The average salinity of the ocean is about 35 parts per thousand (ppt).
What is the difference between salinity and density?
Salinity is the amount of salt in water, while density is the mass of water per unit volume.
What are the main factors that affect salinity?
The main factors that affect salinity are evaporation, precipitation, and runoff.
How does salinity affect the ocean?
Salinity affects the ocean in a number of ways, including its density, temperature, and circulation.
What are the effects of climate change on salinity?
Climate change is causing the ocean to become more saline, which is having a number of effects on the ocean ecosystem.
What are some of the challenges of measuring salinity?
One of the challenges of measuring salinity is that it is a very small change in the total mass of water. Another challenge is that salinity can vary greatly from place to place.
What are some of the ways that salinity is measured?
Salinity can be measured using a number of methods, including conductivity, refractometry, and titration.
What are some of the applications of salinity measurements?
Salinity measurements are used in a number of applications, including Oceanography, fisheries, and water management.
What are some of the future challenges of salinity research?
One of the future challenges of salinity research is to better understand the effects of climate change on salinity. Another challenge is to develop new methods for measuring salinity.
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The ocean covers about ____ of the Earth’s surface.
(A) 71%
(B) 80%
(C) 90%
(D) 97% -
The average depth of the ocean is ____.
(A) 12,000 feet
(B) 13,000 feet
(C) 14,000 feet
(D) 15,000 feet -
The deepest part of the ocean is the Mariana Trench, which is located in the Pacific Ocean. The Mariana Trench is ____.
(A) 35,797 feet deep
(B) 36,070 feet deep
(C) 36,380 feet deep
(D) 36,686 feet deep -
The ocean is home to a variety of marine life, including fish, whales, dolphins, and sea turtles. The ocean is also home to a variety of Plants, including algae and seaweed.
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The ocean is a vital part of the Earth’s ecosystem. The ocean provides us with food, water, and Oxygen. The ocean also helps to regulate the Earth’s climate.
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The ocean is facing a number of threats, including pollution, overfishing, and climate change. We need to take steps to protect the ocean so that it can continue to provide us with the many benefits that it does.
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One way to protect the ocean is to reduce pollution. Pollution can come from a variety of sources, including factories, cars, and farms. We can reduce pollution by using less energy, driving less, and eating less meat.
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Another way to protect the ocean is to reduce overfishing. Overfishing occurs when too many fish are caught. This can lead to the decline of fish populations and the collapse of fisheries. We can reduce overfishing by eating less seafood and by supporting sustainable fisheries.
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Climate change is also a threat to the ocean. Climate change is causing the ocean to become warmer and more acidic. This is harming marine life and coral reefs. We can reduce climate change by reducing our emissions of greenhouse gases.
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We need to take steps to protect the ocean so that it can continue to provide us with the many benefits that it does. We can do this by reducing pollution, reducing overfishing, and reducing climate change.