Ladoga is experiencing the impact of three air masses. Sea air brought by cyclones from the Atlantic causes thaws and heavy snowfalls in winter, and is accompanied by cloudy and windy weather in summer. During the period when continental air masses coming from the south and east dominate over the lake, the coast of Ladoga experiences dry and hot days in summer and frosty days in winter. The established weather can be dramatically changed by the intrusion of cold arctic air from the north, which is always associated with unexpected cold snaps and strong winds.

The lake itself has a noticeable influence on the climate of the coast. From April to July it is cooler near it than in the surrounding areas, and from August to March, on the contrary, it becomes warmer - this is due to the warming effect of Ladoga.

Average annual temperature the air on the Ladoga islands is about +3.5 degrees, and on the coast it varies from +2.6 to +3.8 degrees. Although the length of the lake throughout climate zone relatively small, but some warming to the south and cooling to the east are still noticeable. The most warm place on Ladoga - the southern coast. True, the difference in average monthly air temperatures of the “cold” and “warm” coasts is only a few tenths of a degree. In summer in the south of Ladoga the air can heat up to +32°. The most severe frosts, reaching -54°, ​​are observed on the east coast. The average duration of the warm period on Ladoga ranges from 103 to 180 days, and it is longest on the islands.

Spring comes in April. At this time it is still quite cold on the lake. The average air temperature on the islands and above the lake is slightly above 0, and on the coast from +1.5 to +2.5 degrees. In May and even in June, warm days can suddenly be replaced by frost. With the cessation of frosts and the establishment warm weather Summer begins with temperatures above +10 degrees.

In June, the average monthly air temperature on the islands is already +12/+13, and on the coast – about +14°. During the day, the air can heat up to 20 degrees or more in the shade. The warmest month on Ladoga is July, with an average temperature of +16/+17°.

In August the temperature begins to drop, although in some years it can be the warmest month. Usually the average temperature in August is +15/+16 degrees. Thus, the period from late June to mid-August is the warmest here. At the end of September - beginning of October, the first frosts begin on the coast.

When warm air masses invade from the south in the first half of autumn, there is often a return of warm weather - “Indian summer”. Then clear and warm days may set in even for 2-3 weeks.

In early November, negative temperatures become quite stable. And yet the first half of winter is mild. Often in December there are thaws accompanied by snowfall and rain. In January and February, thaws are less frequent. These are the coldest months - their average temperature is -8/-10, and on some days frosts can reach 40-50 degrees.

Perhaps no climate indicator is so influenced by a lake as relative humidity. The saturation of air with water vapor over the lake and the coast on average for the year is 80-84 percent. The most even distribution of humidity is in winter. In spring and summer, relative humidity along the coast can drop to 60 percent, while above the lake, especially in the southern part and on the islands, it does not fall below 79 percent. In July and August there are often fogs here, quite dense, so that nothing can be seen at a distance of 10 meters.

Despite the relatively weak development of clouds over Ladoga, rainy days occur here quite often - up to 200 per year, with about 600 millimeters of precipitation falling.

Most of the precipitation - up to 380 millimeters - falls in warm time of the year. They are especially abundant in July and August, but are characterized by short showers, followed by stable clear weather. Spring is the driest season on Ladoga.

The distribution of liquid sediments across the lake has its own characteristics. The least amount of them falls in the central part - 325 millimeters. There is more precipitation on the coasts: on the northern and western coasts – 375, and on the southern and southeastern coasts – up to 400 millimeters.

The first snow falls on the shores of Ladoga at the end of October. At the end of November - beginning of December, the snow cover becomes more stable. It gradually grows throughout the winter, reaching its maximum thickness in March - up to 40-50 centimeters.

For most of the year, southerly winds prevail over Ladoga, the southwest wind blows especially often, or, as it was called in the old days, “shelonnik”, after the name of the Sheloni River, which flows into Lake Ilmen and has a similar direction. This name for the wind was transferred to Ladoga by Novgorod navigators and was preserved in the form of inscriptions on compasses until the end of the last century.

In summer, along with southern winds, intrusions of northern and northeastern winds – the “night owl” and “low-water wind” – are quite frequent. average speed prevailing winds are 6-9 m/sec per second over the lake and 4-8 m/sec over the coast. The skerry area of ​​Ladoga, protected by hilly terrain, is characterized by the weakest winds. Their average annual speed barely exceeds 3 meters. The southern coast occupies an intermediate position.

However, on some days the winds can reach great strength - more than 15 m/sec. They occur 60 days a year over the lake and less than 30 days over the coast. The quietest section of the coast is located in the Priozersk area. Only 2-3 days a year there is wind at a speed of more than 15 meters per second. Forested herrings have a positive influence here, protecting relatively large territory from powerful northern air currents.

Winds blowing at a speed of 10-15 meters per second cause strong waves on Ladoga. The height of the waves can reach 3-4 meters at this time. However, such winds usually do not last long - they are observed for 2-3 and much less often - 6-7 days in a row. Winds blowing at a speed of 20-24 meters per second stop after 5-6 hours, and even stronger winds stop after 1 hour. There are cases when in the area of ​​​​the island of Valaam the wind reached 28 and even 34 meters per second.

In the warm season, due to unequal heating of water and land over Ladoga, local winds - breezes - arise. During the day they blow from the lake to the shore - a lake breeze, and at night, on the contrary, from the shore to the lake - a shore breeze.

A characteristic feature of Ladoga winds is their instability during the day. Indeed, the wind can suddenly change its direction in just 20-40 minutes. Such a change often heralds a storm. It was noticed that if there is a short calm over the lake after the western and north-western winds, and then the wind begins to travel from the north and north-east stronger and stronger, then stormy weather can break out within 1-2 hours. “Aeolus is very capricious on the lake,” they used to say about Ladoga in the old days.

Without exaggeration, Lake Ladoga can be called a storehouse of solar energy. The heat flow falling on its surface during the year is measured by an astronomical figure - 14x1015 kilocalories. This heat would be enough to heat the entire mass of Ladoga water by 15 degrees. But in reality it only heats up to 8 degrees. Why does this happen? The fact is that the surface of the lake is a natural mirror, reflecting Sun rays. In summer, the lake reflects 9-10 percent of the rays; in winter, ice-bound Ladoga already releases half of the incoming heat into the atmosphere.

Another reason for losses lies in physical properties water itself - in its weak thermal conductivity. Water is simply not able to fully absorb the heat that the sun gives it.

Due to low thermal conductivity, 65 percent of the heat entering the lake is retained in the upper meter layer of water, and only 1.5 percent of solar energy penetrates to a 100-meter depth.

If water had greater thermal conductivity, the penetration of heat into depth would occur much faster, and its losses would be reduced. True, while slowly heating up, the lake is also slowly cooling down. It retains heat much longer than air, thereby exerting a warming effect on coastal areas.

A large amount of thermal energy is spent on evaporation. Over the course of a year, a layer of water 300 millimeters thick evaporates from Ladoga, which is a volume equal to 5.5 cubic kilometers. It would be enough to fill a lake like Ilmen.

Solar energy penetrating into the water column sets the water masses of the lake in motion. Even during short periods of calm, when the surface of Ladoga is mirror-immobile, at depth there is a movement of water masses both horizontally and vertically. This phenomenon contributes to the redistribution of heat in Ladoga, gradually enriching deeper layers with it.

The accumulation of solar heat and its distribution in water during the day, season, and year determines the temperature regime of the lake. Ladoga has its own spring, summer, autumn and winter.

Spring on Ladoga begins early. In mid-March, the lake is still frozen, but the first gullies and polynyas are already appearing. The ice is darkening and cracking in some places. The ice cover is gradually destroyed, but still serves as a giant screen that reflects the sun's rays. The water temperature under the ice at this time is close to 0 degrees. At a depth of about 30 meters it is +0.16 degrees, 50 meters – +0.67, 100 meters and more +2.4°+2.7 degrees. But as soon as Ladoga sheds its ice shell, intense heating of the water begins. It warms up especially well and quite early in the southern shallow bays. In June, the water temperature on the surface of the Volkhov and Svirskaya bays rises to +16°+17 and even +20 degrees.

At the same time all central part Ladoga is occupied by cold waters, forming a huge “spot” with a temperature below +4 degrees. At the beginning of June it still occupies more than half the area of ​​the lake. It would seem that cold waters should mix with warm ones, but this does not happen. The mixing of water is prevented by the so-called thermal bar, or threshold (thermobar), an interesting natural phenomenon that occurs in spring and autumn in large bodies of water.

It was first noticed at the beginning of this century by the Swiss scientist F.A. Forel, who was studying Lake Geneva. But it so happened that the thermal bar was soon forgotten. And only careful studies carried out on Ladoga in 1957-1962 made it possible to comprehensively assess the importance of the thermal bar for various aspects of the life of the reservoir. In fact, this was a new discovery of a thermal bar made by A.I. Tikhomirov.

The existence of a thermal bar is due to the very nature of water. As is known, unlike other substances, water has its greatest density not in the solid state, but in the liquid state at a temperature of +4 degrees. This feature leads to the fact that in spring and autumn, when such temperatures in the reservoir become possible, a thermal bar appears. It can be compared to a kind of transparent partition made of the densest water, stretching from the surface to the bottom.

It occurs at some distance from the shore at the boundary of two water masses, one of which has a surface temperature below 4 degrees Celsius, and the other much higher. The 4-degree water formed as a result of mixing, as having the highest density, begins to sink to the bottom, drawing more and more portions of surface water into this process. This downward flow of the densest waters is a thermal bar. Having reached the bottom, the dense waters slowly spread out.

The thermobar divides the lake into two regions: a thermally active region, where heating and cooling processes occur more intensely, and a thermally inert region, in which they are greatly slowed down. The thermally active region is located along the coast in the zone of shallower depths, and the thermally inert region occupies the central – deep-sea – part.

It is interesting that in spring the warm waters of the coastal zone and the cold central part of the lake do not mix with each other in any direction of the wind. The currents that arise in the lake do not accelerate this process. The thermobar serves as an excellent natural barrier.

The location of the thermal bar in the lake is quite clearly indicated by a foamy stripe. It is formed where waters converge and mix. different temperatures, after which, having reached maximum density, they will begin their descent. Oil products discharged by ships, small objects and debris floating on the surface of the lake are also drawn here. The thermal bar line is clearly visible from ships and aircraft.

The position of the thermal bar front changes over time. As the lake warms up, the thermally active region becomes larger, pushing the thermal bar towards the center of the lake.

On Ladoga, a thermal bar occurs annually at the end of April - the first half of May and lasts until mid-July. By this time, the entire water column in the lake has time to warm up to +4 degrees. The conditions necessary for the existence of a thermal bar disappear. The summer period begins in the life of Ladoga, and with it the intense heating of its waters. At the end of July, the surface layers of the lake are already quite warmed up, but from a depth of 20-25 meters to the bottom, the lake bowl is still filled with cold, dense waters.

Most warm months on the lake – July and August. The average water surface temperature in these months is 14 and 16 degrees, respectively. However, water in different areas of Ladoga heats up differently. The warmest are the southern shallow bays and the southeastern part, where the water is 4-5 degrees warmer than off the western coast.

At the beginning of September, autumn cooling begins. But simultaneously with the cooling of the surface layers of water, another process is taking place - the penetration of heat into the depths of the lake, which is facilitated by wind mixing, which is most intense in the autumn.

The heat is distributed more and more evenly throughout the lake. Finally, a period comes when the water temperature equalizes everywhere. This condition is called homothermy. It lasts only a few days, and then the stratification of the water column begins again, and reverse thermal stratification is established: warmer water masses are covered with a layer of cold water. Bays, lips and shallow bays cool down first, since the heat accumulated in them is less than in deep-sea areas.

At the end of October - beginning of November, when the water temperature along the coasts drops below +4 degrees, an autumn thermal bar appears above depths of 7-10 meters. It blocks access to warm waters from the central part of the lake and, gradually retreating towards the middle, contributes to the early freezing of shallow waters.

The lake is entering its winter period. On Ladoga, winter lasts three months - from mid-December to mid-March. Freezing occurs gradually - from the shores of bays and bays. At the end of December, the Volkhovskaya, Svirskaya and Petrokrepost bays are covered with ice, the thickness of which in warm winters does not exceed 35-40 centimeters.

In the harsh winter of 1941/42, ice bound the southern lips earlier than usual. This made it possible to send the first convoy of trucks along the “Road of Life” on November 22. The thickness of the ice cover along which the route passed reached 90-110 centimeters by the end of winter. This is its maximum value recorded on Ladoga.

By mid-winter, most of the lake is already covered with ice, with the exception of the area located above great depths. The formation of complete freeze-up on Ladoga is not observed every year. Typically, only 80 percent of the area is covered by ice. There remains a huge polynya in the center, which stretches in the form of a horseshoe from the western shore to the eastern one a little south of the Valaam archipelago. Sometimes, in calm frosty weather, this hole is covered with a thin layer of ice, but then the wind destroys it again.

Ladoga opens up in reverse order compared to freezing. Ice disappears first in the bays, bays and coastal shallows. Most of the ice melts on site and only 3-5 percent of it enters the Neva. In some years, there is no ice drift on the Neva at all - after all, Ladoga ice can enter the Neva only with eastern and northeastern winds. By the end of May the lake is completely cleared of ice.

Two main factors participated in the creation of Ladoga - geology and climate. As a result of geological processes, a bowl of the lake arose, and the climate contributed to its filling and preservation of moisture in a relatively constant volume for thousands of years.

The water reserve in Ladoga is 908 cubic kilometers. This value does not remain constant - in some periods it grows, in others it falls. True, such fluctuations in relation to the total mass of water in the lake did not exceed 6 percent, at least over the last 100 years. They manifest themselves in changes in water level and are sometimes so significant that they even cause low and high water periods in the Ladoga regime.

In the old days, prolonged low levels were often explained by the influence of supernatural forces. Among the inhabitants of the villages scattered along the banks, there were various legends. Maybe because the number 7 was considered lucky in Rus', there was a belief that the water level on Ladoga rises for 7 years and falls for 7 years.

The onset of low-water years in the life of the lake has always been considered an unkind phenomenon. In the XVIII and 19th centuries it especially affected the life of St. Petersburg, economic development which was closely connected with shipping. In low-water years, due to the strong shallowing of the Ladoga canals and the source of the Neva, navigation was difficult and incurred heavy losses. The supply of goods to the city was reduced, food prices began to rise, which is why the poor suffered the most.

An analysis of data on level changes over 100 years showed that the existing folk belief about seven dry years was not true. But it to some extent reflected the main feature of the long-term level regime of Ladoga - its periodicity.

Over the past 100 years, Ladoga has experienced three periods, or cycles; fluctuations in water level with a duration of each within 25-33 years. In each period, two phases are distinguished: low-water and high-water.

Ladoga experienced the closest complete cycle to us in time in 1932-1958. The low-water phase of this period began in 1932, reaching a minimum in 1940. The average annual water level was 1 meter below normal.

At the beginning of the 1940s, a high-water phase began. The average annual level began to rise gradually, reaching its maximum in 1958. The spring flood that year was 2 times greater than usual. The water level in May was 140 centimeters higher than average. Many low-lying areas near the lake were flooded, and some coastal buildings were damaged. Small islands in the skerries were completely submerged under water, and the trees growing on them rose straight out of the water.

Fluctuations in the water level in the lake depend not only on the onset of wetter or drier periods, but are also associated with the seasons of the year. The ascent in Ladoga begins in April-May, from the moment of entry into the lake melt water, and reaches its maximum in June. During these three months, the water level rises by an average of 32 centimeters.

In June, the influx of river waters noticeably decreases, at the same time, the discharge of Ladoga waters across the Neva increases. Already in June the level usually begins to fall. The most recent drop was in 1952, when levels dropped by 37 centimeters during June. The water level is at its lowest in January, when the inflow into the lake and the outflow from it become equal.

Fluctuations in water level on Ladoga often depend on the wind. A strong wind of a constant direction pushes water into bays and bays, causing the level in them to begin to rise rapidly. At the same time, on the opposite bank there is a rush of water, accompanied by a decrease in level. Due to the great depths, near the rocky northern coast, surge phenomena are less developed than in the shallow southern bays.

The calculations showed that for different areas of the lake there is a certain relationship between the magnitude of the surge and the strength of the wind. Wind blowing at a speed of 5 meters per second can cause the level to rise by 8-10 centimeters on the southern coast and by 5-6 centimeters on the northern coast. But a wind of 15 meters can raise the water level in the southern lips by 90 centimeters. True, such surges are extremely rare, but they still happen.

So, on the night of July 5-6, 1929, a storm of such strength broke out over the lake that even the old-timers could not remember anything like it. In a few hours, the water level near the village of Storozhno, near the mouth of the Svir River, rose by 140-150 centimeters. Huge waves rolled onto the shore, breaking trees and moving coastal stones “weighing many pounds.” More for a long time along the shore, at a great distance from the water's edge, lay logs, fragments of trees and bunches of aquatic plants, thrown out by the wave during the storm.

Water surges are observed less frequently, and the drop in level during them is insignificant. True, the ancient manuscript “Appearance in the City of Oreshka,” dating back to 1594, describes an interesting incident: during a storm, the wind drove water from the shallows at the source of the Neva, so that it was possible to ford the river.

On Ladoga there is another type of level fluctuations, also not associated with changes in water supply. These fluctuations arise under the influence external forces, operating a short time, – a strong gusty wind, a sharp change in pressure over some area of ​​the lake, uneven precipitation, etc. After the action of these forces ceases, the entire water mass of the lake begins to move, similar to the vibration of water in a bucket while being carried. These level fluctuations are insignificant - only a few centimeters. They are called a standing wave, or seiche.

During seiches, the level change has a clearly defined periodicity. The length of the period is measured from 10 minutes to 5 hours 40 minutes, during which the water level on the lake gradually rises and also gradually falls. Over time, due to friction against the shores and bottom, the oscillations of the water mass die out, and the surface of the lake takes on a strictly horizontal position. The calm on Ladoga does not last long.

Since ancient times, swimming on the lake was associated with great risk. Thousands of ships perished in its waves. It got to the point that not a single insurance company in Russia insured ships traveling with cargo along Ladoga. Not only the poor equipment of the ships and the lack of good navigation charts affected, but also the natural features of Ladoga. “The lake is stormy and filled with stones,” wrote the famous researcher A.P. Andreev.

The reason for the harsh nature of Ladoga lies in the peculiarities of the structure of its basin, the distribution of depths and the outlines of the lake. A sharp change in the bottom profile during the transition from the great depths of the northern part to the shallow depths of the southern part prevents the formation of a “correct” wave - along the entire length of the lake. Such a wave can only occur in the northern part. When the winds drive it south, it retains its shape only over great depths.

As soon as it gets into an area with depths of 15-20 meters, the wave breaks. She becomes tall, but short. Its crest tips over. Arises a complex system waves going in different directions, the so-called “crush”. It is especially dangerous for small ships that experience sudden, fairly strong shocks. There is a known case when a research vessel, operating at a sea level of 3-4 and a wave height of 0.8 meters, experienced a shock, as a result of which the doors of the closet were torn off their hinges, and the dishes that flew out onto the floor of the wardroom were smashed to pieces.

In the old days, apparently, during such unexpected impacts, the steering failed or damage was caused to the ship's hull, which led to its inevitable death.

Another feature of the excitement on the lake was also noticed. During a storm, waves alternate: a group of 4-5 high and long waves is replaced by a group of lower and shorter ones. Such waves are perceived by the ship as a bumpy road. It causes roll, which negatively affects the condition of the ship's hull.

Studying waves on a lake is associated with great difficulties. The highest wave that was measured on Ladoga was 5.8 meters. According to theoretical calculations, the wave height during a storm here may be higher.

A relatively calm area of ​​Ladoga is the southern lips, where a wave of 2.5 meters occurs only when very strong winds. The quietest month on Ladoga is July. At this time, the lake is mostly calm.

No matter how strong or prolonged the excitement on the lake, the main role in mixing the huge thickness of water still belongs to currents. The accumulation of heat in the lake and its distribution among regions, the purification of water from decay products, the enrichment of it with oxygen, minerals and a number of other processes that determine the life of the reservoir depend on them.

Deep autumn. The days are getting shorter and shorter. The sun will peek out for a minute from behind the heavy clouds, slide across the ground with its oblique ray and disappear again. Cold wind walks freely through empty fields and bare forest, looking for somewhere else a surviving flower or a leaf clinging to a branch in order to pick it, lift it high and then throw it into a ditch, ditch or furrow. In the morning, the puddles are already covered with crispy pieces of ice. Only the deep pond still does not want to freeze, and the wind still ripples its gray surface. But now fluffy snowflakes began to flash. They spin in the air for a long time, as if not daring to fall on the cold, inhospitable ground. Winter is coming.

A thin crust of ice, which first formed near the shores of the pond, creeps into the middle to deeper places, and soon the entire surface is covered with clean transparent glass of ice. Frosts hit, and the ice became thick, almost a meter thick. However, the bottom is still far away. Water remains under the ice even in severe frosts. Why doesn't a deep pond freeze to the bottom? The inhabitants of reservoirs should be grateful for this one of the features of water. What is this feature?

It is known that the blacksmith first heats the iron tire and then puts it on the wooden rim of the wheel. As the tire cools, it will become shorter and fit tightly around the rim. The rails are never laid close to each other, otherwise, when heated in the sun, they will definitely bend. If you pour full bottle oil and place it in warm water, the oil will overflow.

From these examples it is clear that when heated, bodies expand; When cooled they contract. This is true for almost all bodies, but for water this cannot be stated unconditionally. Unlike other bodies, water behaves in a special way when heated. If, when heated, a body expands, it means that it becomes less dense, because the same amount of substance remains in this body, but its volume increases. When heating liquids in transparent vessels, one can observe how warmer and therefore less dense layers rise up from the bottom, and cold ones sink down. This is the basis, by the way, for a water heating device with natural circulation of water. As the water cools in the radiators, it becomes denser, falls down and enters the boiler, displacing upward the water already heated there and therefore less dense.

A similar movement occurs in a pond. Giving up its heat to the cold air, the water cools from the surface of the pond and, being more dense, tends to sink to the bottom, displacing the lower warm, less dense layers. However, such a movement will occur only until all the water has cooled to plus 4 degrees. The water collected at the bottom at a temperature of 4 degrees will no longer rise upward, even if its surface layers had a lower temperature. Why?

Water at 4 degrees has the highest density. At all other temperatures - above or below 4 degrees - water turns out to be less dense than at this temperature.

This is one of the deviations of water from the laws common to other liquids, one of its anomalies (an anomaly is a deviation from the norm). The density of all other liquids, as a rule, starting from the melting point, decreases when heated.

What will happen next when the pond cools down? The upper layers of water become less and less dense. Therefore, they remain on the surface and at zero degrees turn into ice. As it cools further, the ice crust grows, and underneath there is still liquid water with a temperature between zero and 4 degrees.

Here, probably, many people have a question: why doesn’t the lower edge of the ice melt if it is in contact with water? Because the layer of water that is in direct contact with the lower edge of the ice has a temperature of zero degrees. At this temperature, both ice and water exist simultaneously. In order for ice to turn into water, it is necessary, as we will see later, a significant amount of heat. But this warmth is not there. A light layer of water with a temperature of zero degrees separates deeper layers of warm water from the ice.

But now imagine that water behaves like most other liquids. A slight frost would be enough for all rivers, lakes, and perhaps even the northern seas to freeze to the bottom during the winter. Many of the living creatures of the underwater kingdom would be doomed to death.

True, if the winter is very long and severe, then many bodies of water that are not too deep can freeze to the bottom. But in our latitudes this is extremely rare. Ice itself prevents water from freezing to the bottom: it conducts heat poorly and protects the lower layers of water from cooling.

Russian folk tradition- swimming in an ice hole on Epiphany, January 19, attracts more and more more people. This year, 19 ice holes called “font” or “Jordan” were organized in St. Petersburg. The ice holes were well equipped with wooden walkways, and there were rescuers on duty everywhere. And it’s interesting that, as a rule, people swimming told journalists that they were very happy, the water was warm. I myself did not swim in winter, but I know that the water in the Neva, according to measurements, was indeed + 4 + 5 ° C, which is significantly warmer than the air temperature - 8 ° C.

The fact that the temperature of water under ice at depth in lakes and rivers is 4 degrees above zero is known to many, but, as discussions on some forums show, not everyone understands the reason for this phenomenon. Sometimes the increase in temperature is associated with the pressure of a thick layer of ice above the water and the resulting change in the freezing point of water. But most people who successfully studied physics at school will confidently say that the temperature of water at depth is associated with a well-known physical phenomenon - a change in the density of water with temperature. At a temperature of +4°C, fresh water acquires its highest density.

At temperatures close to 0 °C, water becomes less dense and lighter. Therefore, when the water in a reservoir is cooled to +4 °C, the convection mixing of the water stops, its further cooling occurs only due to thermal conductivity (and it is not very high in water) and the water cooling processes slow down sharply. Even in severe frosts, in a deep river under a thick layer of ice and a layer of cold water there will always be water with a temperature of +4 °C. Only small ponds and lakes freeze to the bottom.

We decided to figure out why water behaves so strangely when cooling. It turned out that a comprehensive explanation for this phenomenon has not yet been found. Existing hypotheses have not yet found experimental confirmation. It must be said that water is not the only substance that has the property of expanding when cooled. Similar behavior is also typical for bismuth, gallium, silicon and antimony. However, it is water that is of the greatest interest, since it is a substance that is very important for human life and the entire plant and animal world.

One theory is the existence in water of two types of nanostructures of high and low density, which change with temperature and give rise to an anomalous change in density. Scientists studying the processes of supercooling of melts put forward the following explanation. When a liquid is cooled below its melting point, the internal energy of the system decreases and the mobility of the molecules decreases. At the same time, the role of intermolecular bonds is increasing, due to which various supramolecular particles can be formed. Experiments by scientists with supercooled liquid o_terphenyl suggested that a dynamic “network” of more densely packed molecules could form in a supercooled liquid over time. This grid is divided into cells (areas). Molecular repacking inside a cell sets the rotation speed of molecules in it, and a slower restructuring of the network itself leads to a change in this speed over time. Something similar can happen in water.

In 2009, Japanese physicist Masakazu Matsumoto, using computer modeling, put forward his theory of changes in water density and published it in the journal Physical Review Letters(Why Does Water Expand When It Cools?) As is known, in liquid form, water molecules are combined into groups (H 2 O) through hydrogen bonding. x, Where x- number of molecules. The most energetically favorable combination of five water molecules ( x= 5) with four hydrogen bonds, in which the bonds form a tetrahedral angle equal to 109.47 degrees.

However, thermal vibrations of water molecules and interactions with other molecules not included in the cluster prevent such unification, deviating the hydrogen bond angle from the equilibrium value of 109.47 degrees. To somehow quantitatively characterize this process of angular deformation, Matsumoto and colleagues hypothesized the existence of three-dimensional microstructures in water that resemble convex hollow polyhedra. Later, in subsequent publications, they called such microstructures vitrites. In them, the vertices are water molecules, the role of edges is played by hydrogen bonds, and the angle between hydrogen bonds is the angle between the edges in vitrite.

According to Matsumoto's theory, there is a huge variety of forms of vitritis, which, like mosaic elements, make up the majority of the structure of water and which at the same time evenly fill its entire volume.

The figure shows six typical vitrites that form the internal structure of water. The balls correspond to water molecules, the segments between the balls indicate hydrogen bonds. Rice. from an article by Masakazu Matsumoto, Akinori Baba, and Iwao Ohminea.

Water molecules tend to create tetrahedral angles in vitrites, since vitrites must have the lowest possible energy. However, due to thermal movements and local interactions with other vitrites, some vitrites adopt structurally nonequilibrium configurations that allow the entire system to obtain smallest value energies among the possible. These people were called frustrated. If in unfrustrated vitritis the volume of the cavity is maximum at a given temperature, then frustrated vitritis, on the contrary, have the minimum possible volume. Computer modeling conducted by Matsumoto showed that the average volume of vitrite cavities decreases linearly with increasing temperature. In this case, frustrated vitritis significantly reduces its volume, while the volume of the cavity of unfrustrated vitritis remains almost unchanged.

So, the compression of water with increasing temperature, according to scientists, is caused by two competing effects - the elongation of hydrogen bonds, which leads to an increase in the volume of water, and a decrease in the volume of the cavities of frustrated vitrites. In the temperature range from 0 to 4°C, the latter phenomenon, as calculations have shown, predominates, which ultimately leads to the observed compression of water with increasing temperature.

This explanation is based only on computer simulations so far. It is very difficult to confirm experimentally. Research into the interesting and unusual properties of water continues.

Sources

O.V. Alexandrova, M.V. Marchenkova, E.A. Pokintelitsa “Analysis of thermal effects characterizing the crystallization of supercooled melts” (Donbass National Academy of Construction and Architecture)

Yu. Erin. A new theory has been proposed to explain why water contracts when heated from 0 to 4°C (

IN middle lane In Russia, phenological (natural) winter usually begins in mid-November. By this time, the “off-season” period, so unloved by fishermen, ends with its changes in atmospheric pressure and temperature, alternating frosts and rains, and the vagaries of many species of fish. Fans of winter fishing consider winter to be the period from the formation of stable ice cover to the melting of the ice (from mid-November to the end of March). Sometimes ice cover on reservoirs appears a month to a month and a half later than the beginning of the calendar winter (somewhere in early to mid-January). More often this happens in southern regions Russia. In some regions of the CIS, there is no ice cover on rivers and lakes at all, and the difference between the prolonged autumn and the imperceptibly approaching winter is almost imperceptible.

With the onset of winter, significant changes occur in aquatic systems, affecting the behavior of underwater inhabitants.

Ice cover, lighting and fish behavior.

The importance of light in the life of animals cannot be overestimated. Light “dominates” over all other environmental factors. No environmental factor undergoes such changes as illumination: during the day its intensity changes tens of millions of times (from hundreds of lux to ten-thousandths of a lux). In terms of its intensity and duration, illumination plays the role of a signal for aquatic living organisms as a signal of the beginning of certain changes in the environment (the onset of morning, night, the beginning of warming up of water, etc.), which leads to a change in the behavior of fish.

Throughout autumn and early winter, there is a gradual decrease in daylight hours: in November, the longitude daylight hours on average does not exceed 9 hours 10 minutes. The establishment of ice cover, snowfall, and the predominance of cloudy days further reduce the illumination of water bodies. For four long months, twilight reigns in the underwater kingdom...

The behavior of fish during the initial period of winter is interesting. Many species of heat-loving fish (carp, crucian carp, tench, grass carp) gather in huge schools in October-November and go to the so-called wintering pits. In a semi-stupor, practically not moving, they will spend about three months here (until the end of February). Carp stand very densely at depth, sometimes up to 15-20 individuals per 1 m3, nearby there are asps, ides, and tenches. During severe frosts, bream also coexist with them, but with a change in atmospheric pressure and when the frost weakens, schools of bream leave their wintering pits and “scatter” throughout the reservoir in search of food.

Refuting the generally accepted point of view about the location of the winter “bed” of catfish, river giants occupy places near wintering pits - at the exits from the depths, the boundaries of pits and bottom elevations. This placement of mustachioed predators is explained by the fact that in the pit itself, already a month after the formation of the ice cover, the oxygen regime changes sharply, which this fish, unlike the “thick-skinned” carp (carp), cannot easily tolerate.

Perch, pike, pike perch, after the autumn migration to deeper places (moving away from high water transparency and significant illumination), with the establishment of ice cover, return to their September hunting grounds. Moreover, roach, silver crucian carp, verkhovka and bleak, with rare exceptions, practically do not leave their habitats chosen in the summer.

In shallow and low-food reservoirs, silver crucian carp burrows under leaves or “dives” into the silt. True, only in the northern regions does it stay there for a long time; in more southern areas, the motor activity of crucian carp resumes when the water temperature increases by 3.5 ° C (February). Therefore, during not too cold winters in Ukraine, Kazakhstan and other regions, ice fishing for silver crucian carp is common.

The appearance of ice cover makes adjustments to the behavior of predatory fish. There is such a division of predators in relation to light: perch is considered a twilight-daytime predator, pike - crepuscular, pike perch - deep-twilight.
In autumn, perches and pike feed around the clock: during the day they hunt for prey from ambush, at dusk and at dawn they go out to fish open water and stalk victims. “Twilight” feeding of predators occurs at illumination from hundreds to tenths of lux (in the evening) and vice versa (in the morning). Pike perch can use their vision in conditions where other fish cannot see. The retina of a predator's eye contains a highly reflective pigment - guanine, which increases its sensitivity. The hunt of pike perch for small schooling fish is most successful in deep twilight illumination - 0.001 and 0.0001 lux (almost complete darkness).

At dusk and in the early morning hours, perch and pike have daytime vision with maximum visual acuity and range, and dense defensive schools of prey fish begin to disintegrate, ensuring successful hunting for predators. With the onset of darkness, individual fish disperse throughout the water area; when the illumination drops below 0.01 lux, the top and bleak sink to the bottom and freeze. The hunting of predatory fish stops at this time.

At the beginning of winter, the situation under the ice changes. The twilight plays into the hands of the twilight predators, who in the first days of the establishment of ice cover organize a “St. Bartholomew’s Night” for their demoralized victims. Predatory fish no longer need to distribute their hunting time between early morning and evening hours. This is how the famous “first ice” predator’s gorging begins and continues (usually not for very long).
By the way, in winter, the reaction of prey fish to a threat sharply decreases; tops and bleaks react much weaker to the “smell of fear” emitted by their companions when they are grabbed by a predator.

When searching for a predator in large bodies of water, it is not at all necessary to look for it in holes and snags. Much more often it can be found near areas of ice free of snow: weak, diffused light penetrating into the depths throughout the winter attracts bleak and verkhovka, so beloved by pike perch.

Areas of ice cleared of snow also attract juvenile perches, which gather at a dimly lit area of ​​the “hard surface” of the reservoir after 15-20 minutes. Underwater studies have shown that adult perches, which approach a little later than juveniles, are also attracted to weak light. Moreover, unlike the “minors,” humpback whales avoid the illuminated area and patrol around it in the dark.

Water temperature and fish behavior.

Temperature aquatic environment- the most significant natural factor that directly affects the level of metabolism of poikilothermic (somewhat unfortunate term synonym for “cold-blooded”) animals, which include fish.

All fish, according to the temperature range at which their normal life activity is possible, are divided into heat-loving (roach, carp, crucian carp, tench, herbivorous species (silver carp, grass carp), sturgeon and others) and cold-loving (brook trout, whitefish, salmon , burbot, etc.).

Metabolism in the first representatives is most effective when high temperature. They feed most intensively and are active at a temperature of +17-28°C; when the water temperature drops to +17°C, their feeding activity weakens (and in winter for many species it stops altogether). They spend the pre-winter period and the entire winter in a sedentary state in the deep places of the reservoir.

For cold-loving fish, the optimal temperature is +8-16°C. In winter they feed actively, and their spawning occurs in the autumn-winter period.

It is known that fish “get used to cold weather and a decrease in water temperature”, rebuilding their metabolism in only 17-20 days. When the water temperature decreases from +12°C to +4°C for grayling, for example, energy consumption decreases by 20%.
As the water temperature decreases, the solubility of oxygen increases, so in winter the saturation of water with oxygen is quite high.

With a prolonged decrease in water temperature, fish must not only have a sufficient supply of fat as an energy material, but also maintain normal metabolism during this period.

Fishing strategy in winter.

There are sometimes more fans of winter fishing in certain regions of the CIS than summer fishing enthusiasts. Despite the unpredictable vagaries of the weather and the sometimes inexplicable lack of bite from underwater inhabitants, excellent fishing is possible in winter. You just need to clearly imagine and “calculate” the situation on a specific body of water. You need to know that throughout the winter, at least 20-35 species of fish (in different reservoirs in different ways) continue to feed intensively, sometimes even despite changes in atmospheric pressure.

Naturally, each specific species requires its own, special approach, which will certainly bring success to the fisherman-experimenter if he has some fishing experience, knowledge of the behavior of fish during this period of the year and, of course, a passionate desire to catch his trophy!..

Why doesn’t the water in reservoirs freeze to the very bottom in winter?

Hello!

Temperature of the highest water density: +4 C, see: http://news.mail.ru/society/2815577/

This property of water is fundamentally important for the survival of living creatures in many reservoirs. When the temperature of the air (and, accordingly, the water) begins to decrease in the fall and in the pre-winter period, first, at temperatures above +4 C, the colder water from the surface of the reservoir sinks down (as heavier water), and the warm water, as lighter water, rises up and goes in the usual vertical direction. stirring the water. But as soon as T = +4 C is established vertically in the entire body of water, the process of vertical circulation stops, since from the surface the water already at +3 C becomes lighter than that which is below (at +4 C) and the turbulent heat transfer of cold vertically is sharply reduced. As a result, the water even begins to freeze from the surface, then an ice cover is established, but at the same time, in winter, the transfer of cold to the lower layers of water sharply decreases, since the layer of ice itself on top, and even more so, the layer of snow that fell on the ice from above, have certain thermal insulation properties! Therefore, at the bottom of the reservoir there will almost always be at least a thin layer of water at T = + 4C - and this is the survival temperature of river, swamp, lake and other living creatures in the reservoir. If it were not for this interesting and important property of water (Max density at +4C), then the reservoirs on land would all freeze to the bottom every winter, and life in them would not be so abundant!

All the best!

A very important property of water is at work here. Solid water (ice) is lighter than its liquid state. Thanks to this, the ice is always on top and protects the lower layers of water from frost. Only very small bodies of water can freeze to the bottom in very severe frosts. In ordinary cases, under a layer of ice there is always water, in which all underwater life is preserved.

It all depends on the severity of the frost; sometimes even deep standing reservoirs can freeze to the bottom. if frosts below minus 40 last for several weeks. But basically, indeed, reservoirs do not freeze, which makes it possible for the fish and plants living in them to survive. And the point here is such a curious property of water as a negative coefficient of expansion, which water has at a temperature of +4 degrees and below. That is, if water is heated above 4 degrees, then as its temperature increases, it will tend to occupy a larger volume, its density decreases and it rises. If the water cools below 4 degrees the situation changes to the opposite - than colder water, the lighter it becomes and the lower its density, and therefore the colder layers of water tend to the top, and those with a temperature of +4 - down. Thus, under the ice, the water temperature is set at +4 degrees. The boundary layers of water next to the ice will either flood the ice or freeze themselves, increasing the thickness of the ice until a dynamic equilibrium is established - how much ice will melt from warm water, so much water will freeze from cold ice. Well, everything has already been said about the thermal conductivity of ice.

You missed a lot important point: the highest density of water is at a temperature of +4 degrees. Therefore, before the reservoir begins to freeze, all the water in it, mixing, is cooled to these very plus four, and only then upper layer cools to zero and begins to freeze. Since ice is lighter than water, it does not sink to the bottom, but remains on the surface. In addition, ice has very low thermal conductivity and this sharply reduces the heat exchange between cold air and the layer of water under the ice.