What is called the water mass. Water masses of the ocean

As well as airspace, the water is not homogeneous in its zonal structure. About what is called the water mass, we'll talk in this article. We identify their main types, as well as determine the key hydrothermal characteristics of the oceanic areas.

What is called the water mass of the World Ocean?

Aquatic oceanic masses are relatively large layers of oceanic waters, possessing certain properties (depth, temperature, density, transparency, amount of contained salts, etc.) characteristic for this type of water space. Formation of the properties of a certain type of water masses occurs over a long period of time, which makes them relatively constant and the water masses are perceived as a single whole.

Main characteristics of marine water masses

The aqueous oceanic masses acquire different characteristics in the process of interaction with the atmosphere, differing depending on the degree of impact, as well as on the focus of formation.

1. Temperature is one of the main indicators by which the water masses of the World Ocean are estimated. It is natural that the temperature of surface sea waters finds its extremum in the equatorial latitude, as the distance from it decreases, the water temperature decreases.
2. Salinity. The salinity of water streams is affected by the level of precipitation, the intensity of evaporation, and the amount of fresh water coming from the continents in the form of large rivers. The highest salinity is registered in the basin of the Red Sea: 41 ‰. The salinity map of sea waters is clearly visible in the following figure.
3. The density of water masses directly depends on the depth at sea level they are in. This is explained by the laws of physics, according to which a denser, and therefore a heavier liquid falls below a liquid with a lower density.

The main zones of water masses of the World Ocean

Complex characteristics of water masses are formed under the influence not only of a territorial feature in combination with climatic conditions, but also due to mixing of different water streams. The upper layers of oceanic waters are more prone to mixing and the influence of the atmosphere than the deeper water layers of the same geographic region. In connection with this factor, the water masses of the World Ocean are divided into two large sections:

1. The oceanic troposphere - the upper, the so-called surface layers of water, the lower boundary of which reaches 200-300, and sometimes 500 meters of depth. Differ the most prone to the influence of atmospheric, temperature and climatic conditions. They have different characteristics depending on their territorial location.
2. Oceanic stratosphere - deep waters below surface layers with more stable properties and characteristics. The properties of the water masses of the stratosphere are more stable, since there are no strong and extensive movements of water flows, especially in the vertical section.

Types of waters of the oceanic troposphere

The oceanic troposphere is formed under the influence of a combination of dynamic factors: climate, precipitation, and the tide of continental waters. In connection with this, surface waters have frequent fluctuations in temperature, in the level of salinity. The movement of water masses from one latitude to another forms the formation of warm and cold currents.

Surface waters are most saturated with life forms in the form of fish and plankton. Types of water masses of the oceanic troposphere are divided according to geographical latitudes with a pronounced climatic factor. Let's name the main of them:

• Equatorial.
• Tropical.
• Subtropical.
• Subpolar.
• The polar.

Characteristics of equatorial water masses

The territorial zoning of the equatorial water masses covers a geographic band from 0 to 5 north latitude. The equatorial climate is characterized by an almost equally high temperature regime throughout the calendar year, and therefore the water masses of this region are warmed up to a sufficient degree, reaching a temperature of 26-28.

Due to the precipitation of abundant precipitation and the influx of fresh river water from the continent, the equatorial ocean waters have a small percentage of salinity (up to 34.5 ‰) and the lowest conditional density (22-23). The saturation of the region's aquatic environment with oxygen also has the lowest value (3-4 ml / l) due to the high average annual temperature.

Characteristics of tropical water masses

The zone of tropical water masses occupies two bands: 5-35 northern hemisphere (north-tropical waters) and up to 30 southern (south-tropical waters). Formed under the influence of climate and air masses - trade winds.

The summer temperature maximum corresponds to the equatorial latitude, but in winter this figure drops to the level of 18-20 above zero. The zone is characterized by the presence of ascending water currents from a depth of 50-100 meters off the western coastal continental lines and downward flows near the eastern shores of the continent.

Tropical species of water masses have a salinity index (35-35.5 ‰) and conditional density (24-26) higher than in the equatorial zone. The oxygen saturation of tropical water streams remains approximately at the same level as in the equatorial band, but the phosphate saturation exceeds 1-2 μg-at / l against 0.5-1 μg-at / l in equatorial waters.

Subtropical water masses

The temperature during the year of the subtropical water zone can drop to 15. In tropical latitude, water desalination occurs to a lesser degree than in other climatic zones, since there is a small amount of precipitation here, while intensive evaporation takes place.

Here the salinity of water can reach 38 ‰. The subtropical water masses of the ocean, when cooled in the winter, give off a lot of heat, thereby making a significant contribution to the heat exchange process of the planet.

The boundaries of the subtropical zone reach approximately 45 southern hemisphere and up to 50 n. There is an increase in the saturation of water with oxygen, and thus with forms of life.

Characteristics of the subpolar water masses

As far from the equator, the temperature of the water streams decreases and varies depending on the season. ^о С. So in the territory of the subpolar water masses (50-70 N and 45-60 S) in winter the water temperature drops to 5-7, and in summer it rises to 12-15 ° C.

Salinity of water tends to decrease from subtropical water masses towards the poles. . This is due to the melting of icebergs - sources of fresh water .

Characteristics and features of the polar water masses

Localization of polar ocean masses - near the polar northern and southern spaces, thus, oceanologists identify the presence of Arctic and Antarctic water masses. The distinctive features of polar waters are, of course, the lowest temperature indices: in summer, on average, 0, and in winter 1.5-1.8 below zero, which also affects density - here it is the highest.

In addition to temperature, there is a low salinity (32-33 ‰) due to the melting of continental fresh glaciers. Waters of polar latitudes are very rich in oxygen and phosphates, which favorably affects the diversity of the organic world.

Types and properties of water masses of the oceanic stratosphere

Oceanological stratosphere oceanologists are divided into three types:

1. Intermediate waters cover the water column at a depth of 300-500 m to 1000 m, and sometimes 2000 m. In comparison with the other two types of water masses of the stratosphere, the intermediate layer is the most illuminated, warm and is to a greater extent rich in oxygen and phosphates, and hence Richer underwater world plankton and various species of fish. Under the influence of proximity to the tropospheric water streams, which is dominated by the rapidly flowing water mass, the hydrothermal characteristics and the flow velocity of the water flows of the intermediate layer are very dynamic. The general trend of the movement of intermediate waters is observed in the direction from high latitudes to the equator. The thickness of the intermediate layer of the oceanic stratosphere is not always the same, a broader layer is observed in the polar zones.
2. Deep waters have a range of distribution, starting from a depth of 1000-1200 m, and reach 5 km below sea level and are characterized by more constant hydrothermal data. The horizontal flow of the water flows of this layer is much less than the intermediate waters and is 0.2-0.8 cm / s.
3. The bottom layer of water is least studied by oceanologists in view of its inaccessibility, because they have a depth of more than 5 km from the surface of the water. The main features of the bottom layer are practically constant level of salinity and high density.