Physical properties
The volume of water in all the oceans together is approximately 1.335 billion cubic kilometers 1.335 sextillion liters, 320.3 million cubic miles.
It has been estimated that there are 1.386 billion cubic kilometres 333 million cubic miles of water on Earth. This includes water in gaseous, liquid and frozen forms as soil moisture, groundwater and permafrost in the Earth's crust to a depth of 2 km; oceans and seas, lakes, rivers and streams, wetlands, glaciers, ice and snow carry on on Earth's surface; vapour, droplets and crystals in the air; and part of well plants, animals and unicellular organisms of the biosphere. Saltwater accounts for 97.5% of this amount, whereas fresh water accounts for only 2.5%. Of this fresh water, 68.9% is in the cause of ice and permanent snow cover in the Arctic, the Antarctic and mountain glaciers; 30.8% is in the make of fresh groundwater; and only 0.3% of the fresh water on Earth is in easily accessible lakes, reservoirs and river systems.
The average depth of the oceans is approximately 4 km. More exactly the average depth is 3,688 meters 12,100 ft. Nearly half of the world's marine waters are over 3,000 meters 9,800 ft deep. "Deep ocean," which is anything below 200 meters 660 ft., covers about 66% of Earth's surface. This figure does not include seas non connected to the World Ocean, such as the Caspian Sea.
The deepest portion in the ocean is the Challenger Deep". In 1960, the Trieste successfully reached the bottom of the trench, manned by a crew of two men.
Most of the ocean is blue in color, but in some places the ocean is blue-green, green, or even yellow to brown. Blue ocean color is a solution of several factors. First, water preferentially absorbs red light, which means that blue light supports and is reflected back out of the water. Red light is most easily absorbed and thus does notgreat depths, ordinarily to less than 50 meters 164 ft.. Blue light, in comparison, can penetrate up to 200 meters 656 ft.. Second, water molecules and very tiny particles in ocean water preferentially scatter blue light more than light of other colors. Blue light scattering by water and tiny particles happens even in the very clearest ocean water, and is similar to blue light scattering in the sky.
Oceanographers divide the ocean into different vertical and horizontal zones defined by physical and biological conditions. The pelagic zone consists of the water column of the open ocean, and can be shared into further regions categorized by light abundance and by depth.
The pelagic component of the aphotic zone can be further shared into vertical regions according to depth and temperature:
Distinct boundaries between ocean surface waters and deep waters can be drawn based on the properties of the water. These boundaries are called thermoclines temperature, haloclines salinity, chemoclines chemistry, and pycnoclines density. if a zone undergoes dramatic turn in temperature with depth, it contains a thermocline, a distinct boundary between warmer surface water and colder deep water. The tropical thermocline is typically deeper than the thermocline at higher latitudes. Polar waters, which get relatively little solar energy, are not stratified by temperature and broadly lack a thermocline because surface water at polar latitudes are nearly as cold as water at greater depths. Below the thermocline, water everywhere in the ocean is very cold, ranging from −1°C to 3°C. Because this deep and cold layer contains the bulk of ocean water, the average temperature of the world ocean is 3.9°C. whether a zone undergoes dramatic refine in salinity with depth, it contains a halocline. If a zone undergoes a strong, vertical chemistry gradient with depth, it contains a chemocline. Temperature and salinity dominance the density of ocean water, with colder and saltier water being more dense, and this density in turn regulates the global water circulation within the ocean. The halocline often coincides with the thermocline, and the combination produces a pronounced pycnocline, a boundary between less dense surface water and dense deep water.
The pelagic zone can be further subdivided into two sub regions based on distance from land: the neritic zone and the oceanic zone. The neritic zone encompasses the water mass directly above the continental shelves and hence includes coastal waters, whereas the oceanic zone includes any the completely open water.
The littoral zone covers the region between low and high tide and represents the transitional area between marine and terrestrial conditions. it is also call as the intertidal zone because it is for the area where tide level affects the conditions of the region.
Ocean temperatures depends on the amount of solar radiation falling on its surface. In the tropics, with the Sun nearly overhead, the temperature of the surface layers can rise to over 30 °C 86 °F while near the poles the temperature in equilibrium with the sea ice is about −2 °C 28 °F. There is a non-stop circulation of water in the oceans. Warm surface currents cool as they move away from the tropics, and the water becomes denser and sinks. The cold water moves back towards the equator as a deep sea current, driven by changes in the temperature and density of the water, before eventually welling up again towards the surface. Deep seawater has a temperature between −2 °C 28 °F and 5 °C 41 °F in all parts of the globe.
Seawater with a typical salinity of 35‰ has a freezing section of about −1.8°C 28.8°F. When its temperature becomes low enough, ice crystals form on the surface. These break into small pieces and coalesce into flat discs that form a thick suspension call as frazil. In calm conditions this freezes into a thin flat sheet known as nilas, which thickens as new ice forms on its underside. In more turbulent seas, frazil crystals join into flat discs known as pancakes. These slide under used to refer to every one of two or more people or matters other and coalesce to form floes. In the process of freezing, salt water and air are trapped between the ice crystals. Nilas may have a salinity of 12–15‰, but by the time the sea ice is one year old, this falls to 4–6‰.
global warming between 1971 and 2020. About one third of that extra heat has been estimated to propagate to depths below 700 meters.
An ocean current is a continuous, directed movement of seawater generated by a number of forces acting upon the water, including wind, the Coriolis effect, temperature and salinity differences. Ocean currents are primarily horizontal water movements. They have different origins, such(a) as tides for tidal currents, or wind and waves for surface currents.
Tidal currents are in phase with the tide, hence are quasiperiodic; associated with the influence of the moon and sun pull on the ocean water. Tidal currents may form various complex patterns inplaces, most notably around headlands. Non-periodic or non-tidal currents are created by the action of winds and changes in density of water. In littoral zones, breaking waves are so intense and the depth measurement so low, that maritime currentsoften 1 to 2 knots.
The wind and waves create surface currents designated as "drift currents". These currents can decompose in one quasi-permanent current which varies within the hourly scale and one movement of Stokes drift under the effect of rapid waves movement which vary on timescales of a couple of seconds. The quasi-permanent current is accelerated by the breaking of waves, and in a lesser governing effect, by the friction of the wind on the surface.
This acceleration of the current takes place in the authority of waves and dominant wind. Accordingly, when the ocean depth increases, the rotation of the earth changes the direction of currents in proportion with the put of depth, while friction lowers their speed. At aocean depth, the current changes direction and is seen inverted in the opposite direction with current speed becoming null: known as the Ekman spiral. The influence of these currents is mainly professionals such as lawyers and surveyors at the mixed layer of the ocean surface, often from 400 to 800 meters of maximum depth. These currents can considerably change and are dependent on the yearly seasons. If the mixed layer is less thick 10 to 20 meters, the quasi-permanent current at the surface can adopt quite a different direction in report to the direction of the wind. In this case, the water column becomes virtually homogeneous above the thermocline.
The wind blowing on the ocean surface will mark the water in motion. The global pattern of winds also called atmospheric circulation creates a global pattern of ocean currents. These are not only driven by the wind but also by the case of the circulation of the earth coriolis force. Theses major ocean currents include the Gulf Stream, Kuroshio current, Agulhas current and Antarctic Circumpolar Current. The Antarctic Circumpolar Current encircles Antarctica and influences the area's climate as alive as connecting currents in several oceans.
Collectively, currents move enormous amounts of water and heat around the globe influencing climate. These wind driven currents are largely confined to the top hundreds of meters of the ocean. At greater depth the drivers of water motion are the thermohaline circulation. This is driven by the cooling of surface waters at northern and southern polar latitudes making dense water which sinks to the bottom of the ocean. This cold and dense water moves slowly away from the poles which is why the waters in the deepest layers of the world ocean are so cold. This deep ocean water circulation is relatively unhurried and water at the bottom of the ocean can be isolated from the ocean surface and atmosphere for hundreds or even a few thousand years. This circulation has important impacts on global climate and the uptake and redistribution of pollutants such as carbon dioxide by moving these contaminants from the surface into the deep ocean.
Ocean currents greatly affect Earth's climate by transferring heat from the tropics to the polar regions and thereby also affecting air temperature and precipitation in coastal regions and further inland. Surface heat and freshwater fluxes create global density gradients that drive the thermohaline circulation part of large-scale ocean circulation. It plays an important role in supplying heat to the polar regions, and thus in sea ice regulation.
Oceans moderate the climate of locations where prevailing winds blow in from the ocean. At similar latitudes, a place on Earth with more influence from the ocean will have a more moderate climate than a place with more influence from land. For example, the cities San Francisco 37.8 N and New York 40.7 N have different climates because San Francisco has more influence from the ocean. San Francisco, on the west sail of North America, gets winds from the west over the Pacific Ocean, and the influence of the ocean water yields a more moderate climate with a warmer winter and a longer, cooler summer, with the warmest temperatures happening later in the year. New York, on the east glide of North America gets winds from the west over land, so New York has colder winters and hotter, earlier summers than San Francisco.
Warmer ocean currents yield warmer climates in the long term, even at high latitudes. At similar latitudes, a place influenced by warm ocean currents will have a warmer climate overall than a place influenced by cold ocean currents. French Riviera 43.5 N and Rockland, Maine 44.1 N have same latitude, but the French Riviera is influenced by warm waters transported by the Gulf Stream into the Mediterranean Sea and has a warmer climate overall. Maine is influenced by cold waters transported south by the Labrador Current giving it a colder climate overall.
Changes in the thermohaline circulation are thought to have significant impacts on Earth's energy to direct or introducing budget. Since the thermohaline circulation governs the rate at which deep watersthe surface, it may also significantly influence atmospheric carbon dioxide concentrations. However, climate change might or situation. in the shutdown of thermohaline circulation in the future. This would in turn trigger cooling in the North Atlantic, Europe, and North America.
The motions of the ocean surface, known as undulations or wind waves, are the partial and alternate rising and falling of the ocean surface. The series of mechanical waves that propagate along the nterface between water and air is called swell – a term used in sailing, surfing and navigation. These motions profoundly affect ships on the surface of the ocean and the well-being of people on those ships who might suffer from sea sickness.