As well as the air space, the water space is heterogeneous in its zonal structure. About what is called the water mass, we will talk in this article. We will identify their main types, as well as determine the key hydrothermal characteristics of ocean areas.
What is called the water mass of the oceans?
Water oceanic masses are relatively large layers of oceanic waters that have certain properties (depth, temperature, density, transparency, amount of s alts contained, etc.) characteristic of this type of water space. The 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 whole.
Main characteristics of marine water masses
Water ocean masses in the process of interaction with the atmosphere acquirevarious characteristics that differ depending on the degree of impact, as well as on the source of formation.
- Temperature is one of the main indicators by which the assessment of the water masses of the World Ocean takes place. It is natural that the temperature of surface sea waters finds its extreme in the equatorial latitude, as the distance from which the water temperature decreases.
- Salinity. The salinity of water flows is affected by the level of precipitation, the intensity of evaporation, as well as the amount of fresh water coming from the continents in the form of large rivers. The highest salinity was recorded in the Red Sea basin: 41‰. The salinity map of sea waters is clearly visible in the following figure.
- The density of water masses directly depends on how deep they are from sea level. This is explained by the laws of physics, according to which a denser, and therefore heavier, liquid sinks below a liquid with a lower density.
Main water mass zones of the oceans
The complex characteristics of water masses are formed under the influence of not only a territorial feature in combination with climatic conditions, but also due to the mixing of different water flows. The upper layers of ocean waters are more susceptible to mixing and atmospheric influence than the deeper waters of the same geographic region. In connection with this factor, the water masses of the World Ocean are subdividedinto two large sections:
- Oceanic troposphere - the upper, so-called surface layers of water, the lower limit of which reaches 200-300, and sometimes 500 meters of depth. Differ in the most subject to influence from atmospheric, temperature and climatic conditions. They have heterogeneous characteristics depending on the territorial affiliation.
- Oceanic stratosphere - deep waters below the 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 this regard, surface waters have frequent fluctuations in temperature and salinity levels. The movement of water masses from one latitude to another forms the formation of warm and cold currents.
The highest saturation of life forms in the form of fish and plankton is observed in surface waters. Types of water masses of the oceanic troposphere are usually subdivided according to geographical latitudes with a pronounced climatic factor. Let's name the main ones:
- Equatorial.
- Tropical.
- Subtropical.
- Subpolar.
- Polar.
Characteristics of equatorial water masses
Territori althe zonality of the equatorial water masses covers the geographic band from 0 to 5 north latitude. The equatorial climate is characterized by almost equally high temperature conditions throughout the calendar year, therefore, the water masses of this region are warmed up sufficiently, reaching a temperature mark of 26-28.
Due to heavy precipitation and inflow of fresh river water from the mainland, equatorial oceanic waters have a small percentage of salinity (up to 34.5‰) and the lowest relative density (22-23). The saturation of the aquatic environment of the region with oxygen also has the lowest rate (3-4 ml/l) due to the high average annual temperature.
Characteristic of tropical water masses
The zone of tropical water masses occupies two bands: 5-35 of the northern hemisphere (north-tropical waters) and up to 30 of the southern hemisphere (south-tropical waters). They are formed under the influence of climate features and air masses - trade winds.
The summer temperature maximum corresponds to the equatorial latitude, but in winter this figure drops to 18-20 above zero. The zone is characterized by the presence of ascending water flows from a depth of 50-100 meters near the western coastal continental lines and downward flows near the eastern coasts of the mainland.
Tropical species of water masses have a higher salinity index (35–35.5‰) and relative density (24–26) than that of the equatorial zone. The oxygen saturation of tropical water streams remains approximately at the same level as that of the equatorial strip, but the saturation with phosphates exceeds: 1-2mcg-at/l versus 0.5-1 mcg-at/l in equatorial waters.
Subtropical water masses
The temperature during the year in the subtropical water zone can drop to 15. In the tropical latitude, desalination occurs to a lesser extent than in other climatic zones, since there is little rainfall, while there is intense evaporation.
Here the salinity of water can reach up to 38‰. The subtropical water masses of the ocean, when cooled in the winter season, give off a lot of heat, thereby making a significant contribution to the process of the planet's heat exchange.
The borders of the subtropical zone reach approximately 45th of the southern hemisphere and up to 50th north latitude. There is an increase in the saturation of water with oxygen, and hence with life forms.
Characteristics of subpolar water masses
As you move away from the equator, the temperature of water flows decreases and varies depending on the time of year. So in the territory of 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 12-15o C.
Water salinity tends to decrease from subtropical water masses towards the poles. This happens due to the melting of icebergs - sources of fresh water.
Characteristics and features of polar water masses
Localization of polar ocean masses - near-continental polar northern and southern spaces, thus, oceanologists distinguish the presence of Arctic and Antarctic water masses. Distinctive featurespolar waters are, of course, the lowest temperature indicators: in summer, on average, 0, and in winter, 1.5-1.8 below zero, which also affects the density - here it is the highest.
In addition to temperature, low salinity (32-33‰) is also observed due to the melting of continental fresh glaciers. The waters of the polar latitudes are very rich in oxygen and phosphates, which favorably affects the diversity of the organic world.
Types and properties of water masses in the oceanic stratosphere
Oceanologists conventionally divide the oceanic stratosphere into three types:
- Intermediate waters cover water layers at a depth of 300-500 m to 1000 m, and sometimes 2000 m. Compared to the other two types of water masses of the stratosphere, the intermediate layer is the most illuminated, warmest and more phosphates, which means the underwater world is richer in plankton and various types of fish. Under the influence of the proximity to the water flows of the troposphere, which is dominated by a rapidly flowing water mass, the hydrothermal characteristics and the speed of the flow of water flows of the intermediate layer are very dynamic. The general tendency 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 the same everywhere, a wider layer is observed in the polar zones.
- Deep waters have an area of distribution, starting from a depth of 1000-1200 m, and reaching up to 5 km below sea level and are characterized by more constant hydrothermal data. The horizontal flow of water flows of this layer is much less than the intermediate ones.water and is 0.2-0.8 cm/s.
- The bottom layer of water is the least studied by oceanologists due to its inaccessibility, because they are located at a depth of more than 5 km from the surface of the water. The main features of the bottom layer are the almost constant level of salinity and high density.
