The creation of sea ice and the evaporation of ocean water both increase the salinity of the ocean. These "salinity-raising" forces, however, are constantly counterbalanced by processes that lower salinity, such as the continuous influx of fresh water from rivers, precipitation of rain and snow, and ice melting. The net result is a relatively stable ratio between saltiness and freshness of ocean water.
The concentration of dissolved salts in seawater affects the biology of marine organisms. High concentrations of soluble salts hinder their ability to extract oxygen from air or water while also diminishing their ability to filter food from the water. Low levels of dissolved solids therefore allow for the evolution of more complex organisms with greater needs for oxygen gas and nutrients.
Seawater has a constant density regardless of its composition. Therefore, to remain buoyant, an object in seawater must contain more volume of water than it does of other substances such as sand or rock. An iceberg is primarily made up of ice, which is less dense than seawater. Thus, when an iceberg melts, it leaves behind a pool of salty water called an ice hole or ice pit. As more and more ice holes form, they can be seen floating on the surface of the sea like small islands.
An ice hole forms when an iceberg breaks off from a glacier and sinks to the bottom of the ocean. As the ice melts, it releases fresh water that fills the void left by the lost piece of ice.
Evaporation raises the salinity of saltwater because salts are left behind as seawater evaporates, increasing their concentration. When ice melts, the freshwater inflow dilutes the salt content and reduces salinity. The amount of fresh water entering the ocean from melting ice is called the meltwater input.
Evaporation also affects the salinity of ocean water by controlling the amount of salt that flows into or out of oceans. If more salt enters the ocean than leaves it, then the sea will become more salty and less able to support life. This is called an "evaporative deficit" and can happen when more rain falls as sweat or liquid body heat than evaporates via wind or water movement, for example. An "evaporative surplus" would be when more salt leaves the ocean than enters it; this often happens when there is a lot of precipitation but little surface water movement, such as over arid land areas. Evaporative changes to the salinity of ocean water are one factor that influences current patterns in coastal waters. For example, if the amount of salt in ocean water increases, then less fresh water will enter coastal bays and estuaries through rainfall alone, so more of the incoming tide will reach the shoreline. This can have important effects for marine ecosystems where freshwater inflows from rivers are significant.
Salinity fluctuates with the water cycle! The water cycle influences ocean salinity. When salt water evaporates or freezes, the salt is left behind, increasing salinity. Precipitation and runoff, on the other hand, dilute salt water, lowering salinity. The interaction between these two processes determines how much salt is dissolved in the oceans.
In conclusion, the water cycle affects ocean salinity, which in turn affects marine ecosystems. For example, increased evaporation from dry areas causes salinity to rise, so fish migrate to wetter habitats where they can swim in saline waters without dying. This migration affects which species are able to live in different parts of the ocean. Also, precipitation causes salinity to drop, so rivers flow more slowly into the ocean, changing the nature of river deltas. These are just two examples of how the water cycle affects marine ecosystems; there are many more ways in which the cycle influences life in the seas.
Higher salinity areas There are regions of the ocean where there is little rain, yet warm, dry winds create a lot of evaporation. This evaporation eliminates water; when water vapour travels into the atmosphere, it leaves behind the salt, increasing the saltiness of the saltwater. As a result, the ocean becomes denser. These are called arid zones and they cover most of northern Africa, much of South America, and parts of Australia and California. The Red Sea is an example of an arid zone sea.
Oceans where there is no rain but lots of snow Geothermal energy from deep within the earth keeps our planet warm, but also causes the surface to melt ice and snow. When this water vaporizes, it leaves behind salt, so the water becomes more salty. The Antarctic Ocean is an example of an ocean where there is no rain but lots of snow. These areas are called frozen deserts because the majority of the water is locked up as ice.
Oceans where there is no rain but some lakes In places like North America and Europe, there are areas where it never rains but instead has fog or clouds that move in from the ocean. The ocean absorbs the moisture from these clouds and turns it back into water vapor that escapes into space. When this happens, the ocean becomes more saline because there's no fresh water running into it to dilute its concentration of salt.
Evaporation transports fresh water vapor from the ocean to the atmosphere, resulting in greater salinity. As one moves closer to the poles, fresh water from melting ice reduces surface salinity once more. Adding salt to water reduces the freezing point. This makes sense because it takes more energy to freeze salty water than fresh water.
Also, rainfall and snowmelt transport salt into lakes and oceans. The amount of salt that reaches these bodies of water comes from the amount of salt in their watersheds. If a lake or ocean loses much salt through evaporation or precipitation, then it must replace those salts with something else. Typically, this happens by drawing down the concentration of salt in its basin which leads to further evaporative loss or inflow of freshwater from rivers.
Finally, volcanic activity can also add salt to surface waters. When lava flows into the sea, it leaves a salt crust behind. Lagoons created by flowing lava are often very salty due to the presence of this crust.
Lakes contain more fresh water than seas because they are land-based reservoirs of water. Lakes accumulate runoff water from surrounding areas and meltwater from glaciers, while seas absorb most of these sources of fresh water.
The content of salt in the water increases in areas where evaporation is significant owing to winds and high temperatures. As a result, salinity values in areas of water exposed to strong trade winds are often greater. Ocean water salinity is measured in parts per thousand. The most common unit used by scientists is "psu". One psu is equal to 1 gram per liter. So, for example, if the salinity of water is 15 psu, it means that there is 1 gram of salt in every 100 ml of water.
Ocean waters contain about 33 grams of salt per kilo (2.2 pounds). If all the salt were to be dissolved, ocean water would be nearly saturated with salt. However, much of it is not dissolved but rather exists as tiny particles floating in the water. It is also worth mentioning that some regions of the ocean have less salt than others - these are known as "salt lakes". Salt lakes occur when there is too much evaporative demand on surface water bodies so that they can't absorb any more moisture from the air. Water must then go somewhere else, so it flows into the low-lying lands or even inland seas. There, it picks up additional salt from the soil or rock formation around it. These salty waters then return to the main body of the lake or ocean where they mix with other, less salty waters.