Ice properties: structure, mechanical and physical properties of ice. Sea ice Fresh water on Earth
Ice- mineral with chem. formula H 2 O is water in the crystalline state.
The chemical composition of ice: H - 11.2%, O - 88.8%. Sometimes contains gaseous and solid mechanical impurities.
In nature, ice is mainly represented by one of several crystalline modifications, stable in the temperature range from 0 to 80°C, with a melting point of 0°C. There are 10 crystalline modifications of ice and amorphous ice. The most studied is ice of the 1st modification - the only modification found in nature. Ice occurs in nature in the form of ice proper (mainland, floating, underground, etc.), as well as in the form of snow, frost, etc.
See also:
STRUCTURE
The crystal structure of ice is similar to the structure: each H 2 0 molecule is surrounded by four molecules closest to it, located at equal distances from it, equal to 2.76Α and located at the vertices of a regular tetrahedron. Due to the low coordination number, the ice structure is openwork, which affects its density (0.917). Ice has a hexagonal spatial lattice and is formed by freezing water at 0°C and atmospheric pressure. The lattice of all crystalline modifications of ice has a tetrahedral structure. Parameters of the unit cell of ice (at t 0°C): a=0.45446 nm, c=0.73670 nm (c is twice the distance between adjacent main planes). As the temperature decreases, they change very little. H 2 0 molecules in the ice lattice are linked by hydrogen bonds. The mobility of hydrogen atoms in the ice lattice is much higher than the mobility of oxygen atoms, due to which the molecules change their neighbors. In the presence of significant vibrational and rotational motions of molecules in the ice lattice, translational jumps of molecules from the site of their spatial connection occur with a violation of further ordering and the formation of dislocations. This explains the manifestation of specific rheological properties in ice, which characterize the relationship between irreversible deformations (flow) of ice and the stresses that caused them (plasticity, viscosity, yield strength, creep, etc.). Due to these circumstances, glaciers flow similarly to highly viscous fluids, and thus, natural ice actively participates in the water cycle on Earth. Ice crystals are relatively large (transverse size from fractions of a millimeter to several tens of centimeters). They are characterized by the anisotropy of the viscosity coefficient, the value of which can vary by several orders of magnitude. Crystals are capable of reorientation under the influence of loads, which affects their metamorphism and the speed of glacier flow.
PROPERTIES
Ice is colorless. In large clusters, it acquires a bluish tint. Glass luster. Transparent. Has no cleavage. Hardness 1.5. Fragile. Optically positive, refractive index very low (n = 1.310, nm = 1.309). In nature, 14 modifications of ice are known. True, everything, except for the ice that is familiar to us, which crystallizes in the hexagonal syngony and is designated as ice I, is formed under exotic conditions - at very low temperatures (about -110150 0С) and high pressures, when the angles of hydrogen bonds in the water molecule change and systems are formed, other than hexagonal. Such conditions are reminiscent of cosmic conditions and are not found on Earth. For example, at temperatures below -110 ° C, water vapor precipitates on a metal plate in the form of octahedrons and cubes several nanometers in size - this is the so-called cubic ice. If the temperature is slightly above –110 °C, and the vapor concentration is very low, a layer of exceptionally dense amorphous ice forms on the plate.
MORPHOLOGY
Ice is a very common mineral in nature. There are several types of ice in the earth's crust: river, lake, sea, ground, firn and glacier. More often it forms aggregate accumulations of fine-grained grains. Also known are crystalline formations of ice that arise by sublimation, that is, directly from the vapor state. In these cases, the ice has the appearance of skeletal crystals (snowflakes) and aggregates of skeletal and dendritic growth (cave ice, frost, hoarfrost, and patterns on glass). Large, well-cut crystals are found, but very rarely. N. N. Stulov described ice crystals of the northeastern part of Russia, found at a depth of 55-60 m from the surface, having an isometric and columnar appearance, with the length of the largest crystal being 60 cm and the diameter of its base being 15 cm. forms on ice crystals, only faces of a hexagonal prism (1120), a hexagonal bipyramid (1121), and a pinacoid (0001) were revealed.
Ice stalactites, colloquially called "icicles", are familiar to everyone. With temperature differences of about 0 ° in the autumn-winter seasons, they grow everywhere on the surface of the Earth with slow freezing (crystallization) of flowing and dripping water. They are also common in ice caves.
Ice banks are strips of ice cover from ice crystallizing at the water-air boundary along the edges of reservoirs and fringing the edges of puddles, banks of rivers, lakes, ponds, reservoirs, etc. with the rest of the water area not freezing. With their complete coalescence, a continuous ice cover is formed on the surface of the reservoir.
Ice also forms parallel columnar aggregates in the form of fibrous veinlets in porous soils, and ice antholiths on their surface.
ORIGIN
Ice is formed mainly in water basins when the air temperature drops. At the same time, ice porridge, made up of ice needles, appears on the surface of the water. From below, long ice crystals grow on it, in which the sixth-order symmetry axes are perpendicular to the surface of the crust. The ratios between ice crystals under different conditions of formation are shown in fig. Ice is widespread wherever there is moisture and where the temperature drops below 0 ° C. In some areas, ground ice thaws only to an insignificant depth, below which permafrost begins. These are the so-called permafrost regions; in the areas of distribution of permafrost in the upper layers of the earth's crust, there are so-called underground ice, among which modern and fossil underground ice are distinguished. At least 10% of the entire land area of the Earth is covered by glaciers, the monolithic ice rock that composes them is called glacial ice. Glacial ice is formed mainly from the accumulation of snow as a result of its compaction and transformation. The ice sheet covers about 75% of the area of Greenland and almost all of Antarctica; the largest thickness of glaciers (4330 m) was established near Baird Station (Antarctica). In central Greenland, the thickness of the ice reaches 3200 m.
Ice deposits are well known. In areas with long cold winters and short summer, as well as in high mountainous regions, ice caves with stalactites and stalagmites are formed, among which the most interesting are Kungurskaya in the Perm region of the Urals, as well as the Dobshine cave in Slovakia.
Sea ice forms when sea water freezes. Characteristic properties sea ice are salinity and porosity, which determine the range of its density from 0.85 to 0.94 g / cm 3. Due to such a low density, ice floes rise above the surface of the water by 1/7-1/10 of their thickness. Sea ice begins to melt at temperatures above -2.3°C; it is more elastic and more difficult to break apart than freshwater ice.
APPLICATION
In the late 1980s, the Argonne laboratory developed a technology for the manufacture of ice slurry (Ice Slurry), capable of freely flowing through pipes of various diameters, without gathering into ice buildups, without sticking together and without clogging cooling systems. Salt water suspension consisted of many very small rounded ice crystals. Thanks to this, the mobility of water is preserved and, at the same time, from the point of view of thermal engineering, it is ice, which is 5-7 times more effective than plain cold water in the cooling systems of buildings. In addition, such mixtures are promising for medicine. Animal experiments have shown that microcrystals of the ice mixture pass perfectly into fairly small blood vessels and do not damage cells. Frozen Blood extends the time it takes to save an injured person. For example, during cardiac arrest, this time lengthens, according to conservative estimates, from 10-15 to 30-45 minutes.
The use of ice as a structural material is widespread in the circumpolar regions for the construction of dwellings - igloos. Ice is part of the Pikerite material proposed by D. Pike, from which it was proposed to make the world's largest aircraft carrier.
Ice (English Ice) - H 2 O
CLASSIFICATION
| Strunz (8th edition) | 4/A.01-10 |
| Nickel-Strunz (10th edition) | 4.AA.05 |
| Dana (8th edition) | 4.1.2.1 |
| Hey's CIM Ref. | 7.1.1 |
Info-lesson on the topic PARONYMS ICE - ICE
Info Lesson Plan:
1. Lexical meaning of paronyms icy - icy
2. Examples of phrases with a paronym ice
3. Examples of sentences with a paronym ice
4. Examples of phrases with a paronym ice
5. Examples of sentences with a paronym ice
1. LEXICAL MEANING OF PARONYMS ICE - ICE
ICE- 1) located, located on the ice;
2) occurring in ice.
ICE- 1) consisting of ice, covered with ice;
2) very cold (cold as ice);
3) (transfer.) extremely restrained, contemptuously cold, destroying.
2. EXAMPLES OF PHRASES WITH A PARONYM - ICE
1) ice continent
2) ice palace
3) ice stadium
4) ice airport
5) ice trip
6) ice road
7) ice track
8) ice rink
9) ice field
10) ice expedition
11) Battle on the Ice
12) ice fun
13) ice regime
14) ice barrier
15) ice jams
16) ice barrier
17) ice blockage
18) ice crossing
3. EXAMPLES OF OFFERS WITH A PARONNYM - ICE
1) Water temperature Barents Sea at different depths during the year is not constant, since the amount of warm water brought by the North Cape current. It varies depending on the season. This also affects ice sea mode.
2) When meeting with ice In the field, the icebreaker “creeps” with its bow on the ice edge and breaks it.
3) Exploring Antarctica, Captain Nemo gets into ice captivity.
4) The first Heroes of the Soviet Union were Soviet pilots who saved the expedition of the Chelyuskin steamer, which fell into ice captivity.
5) Up to 4 km in height above sea level rises ice Shield of Antarctica.
6) "Road of life" - ice
8) Work ice roads, "roads of life", were hampered by enemy aircraft.
9) Communication with Leningrad was maintained only by air and through Lake Ladoga, through which it was laid in winter ice track - the legendary "road of life".
10) In the center of Russia, along the mighty Yenisei River, lies Siberian land - a region that is called taiga, although it is mountainous, and tundra, and arctic, and ice.
11)Ice drift lasted 4 months.
12) People say: November is leafy, semi-winter, ice blacksmith.
13) Classes are held in the gym and on ice site.
14)Ice the regime plays a big role in the life of Lake Baikal.
15)Ice the regime of the river is very complex.
16) Even in Antarctica there are people who study ice cover, relief and climate of the mainland.
17) In 1821, Thaddeus Faddeevich Bellingshausen, together with Mikhail Petrovich Lazarev, penetrated ice barrier that surrounded the South Pole.
18) Glacier - ice hat on the tops of the mountains.
19) In the northern part of the Atlantic, where busy sea routes lie, a special ice patrol.
20) Bobsleigh - a sport that is a downhill from the mountains on specially equipped ice trails on controlled sledges - beans.
21) In the summer of 1956, within the framework of the Third International Geophysical Year, a high-latitude Arctic expedition was carried out to explore the strait between Greenland and Svalbard by scientists from the USSR, Sweden and Norway. The program of work provided for the landing of an international group of scientists on ice the dome of Northern Svalbard, and a MI-4 helicopter was assigned to perform this task, commanded by test pilot R.I. Kaprelyan.
22)Ice the shell on Baikal lasts from 4.5 to 6 months.
23) Ice hockey - a sports team game on ice
24) In winter, where it works ice crossing, put signs about the permissible load on this road.
25) In 1242, at sunrise, on the ice of Lake Peipsi, a famous battle took place, called Ice carnage.
4. EXAMPLES OF PHRASES WITH A PARONYM - ICE
1) ice zone
2) ice continent
3) ice peaks
4) ice block
5) ice mountain
6) ice shore
7) ice track
8) ice wave
9) ice cover
10) ice edge
11) ice world
12) ice cave
13) ice wind
14) ice frost
15) ice water
16) freezing rain
17) ice groats
18) ice crumb
19) ice icicle
20) ice crystal
21) ice crust
22) ice ball
23) ice wand
24) ice tone
25) ice look
26) ice trick
27) ice fingers
5. EXAMPLES OF OFFERS WITH A PARONYM - ICE
1) Antarctica - ice mainland.
2)In icy The cover of Antarctica contains about 80% of all fresh water on Earth and 90% of the volume of all natural ice planets.
3) Fish are splashing in ice water.
4)Icy the surface of the pond had been covered with a thick layer of snow since the beginning of winter.
5) The boy on a sled went down from ice slides.
6) The waters of the mighty ocean are bound by ice. Dead white desert look boundless icy fields with frozen blocks of ice. They are called hummocks. (N.I. Sladkov. From north to south ...)
7) It's blowing from the north ice wind.
8) The face is covered in one moment ice crust, and icicles grow on the eyebrows and beard.
9)He went around this giant icy fields, trying to find a passage in the ice, and as a result completely went around this ice array.
10) Kungurskaya icy the cave is a unique monument of nature.
11) Kungurskaya icy the cave was formed on the site of the Great Perm Sea 10 - 12 thousand years ago.
12)Icy the surface of East Antarctica is more flat and high (up to 4000 meters).
13) If the main difficulty in studying the relief icy domes are climatic conditions, making it difficult to carry out geodetic work and aerial surveys, then in order to study the under-ice relief, one must also learn to see through the ice. It can only geophysics. Therefore, she owns the main word about the structure of Antarctica.
14) From small icy crystals in the clouds form snowflakes.
15) The Arctic is divided into two zones: icy zone and zone of arctic deserts.
16)Icy the zone is the seas of the Arctic Ocean together with the islands.
17) On the islands of the Arctic is located icy zone.
18) South ice areas along the coast northern seas extended tundra.
19) Sokuy - one of the types of ice on Lake Baikal. It is formed in the initial phase of freezing of the lake in the form of a thin ice edges - take care, or in the fall from splashes of waves on rocks and stones.
20) Snowflake is ice crystal with hexagonal symmetry.
21) Snow is precipitation in the form icy crystals.
22) Fluffy icy frost covered the branches.
23) Gerda managed to melt icy Kai's heart
24) Hanging a bag outside the window ice,
It is full of drops and smells like spring. (Icicle)
25) High sheer cliffs icy The coastline is an insurmountable barrier.
27) In icy The cover of Antarctica contains 80% of all fresh water on the planet. The surface of the mainland icy shield is covered with a layer of snow.
28) In March-April 2002 from icy An iceberg more than 70 km long separated from the Antarctic shield, which is a rarity and is considered as one of the evidence of modern climate warming.
29) And who has been there [in Antarctica] once, he will always remember the great silence ice desert, painted in the morning in a gentle glow, lilac and pink tones of the bed, cold flashes and aurora borealis, cozy lights of winter quarters, covered with snowdrifts. (According to A.M. Gusev)
30) How can fresh water contained in glaciers be used? The project of transporting icebergs to countries with an arid climate began to be developed in the 20th century. Several methods have been proposed to solve this problem. One of them is the crushing of the iceberg on the spot, loading the resulting ice crumbs in tankers and further transportation to the destination. The advantage of this method is that in this case you do not have to worry about melting - the resulting water will splash reliably in the tanker. The obvious downside is the cost.
31) Winter is a wonderful season. Her icy beauty captivates and inspires admiration.
32) Lovers of swimming in winter in ice water are called walruses.
33) In ice
34)Ice
35) On the last day of Shrovetide, women, celebrating the end of spinning, rolled with ice mountains on the bottoms of the spinning wheels, while it was believed that the farther they go, the longer the flax will be born.
36)Ice cover makes the life of underwater inhabitants difficult.
37) Polar bear inhabits icy expanses and islands of the Polar Basin south to northern coasts Siberia and North America.
38) In which fairy tale the evil queen took the boy to her ice Castle?
39) The polar bear is often called the tireless wanderer of the Arctic. Most often, he can be seen slowly wandering among the endless snow fields or icy hummocks. This huge beast has iron muscles. From the cold it is covered with a thick layer of fat and a white or slightly golden skin with thick wool. Even the soles of the paws are protected by fur. The beast is able to swim in ice open ocean water cover distances of tens of kilometers.
40) Igloo - ice home of the natives of northern North America.
6.TESTS
1)ice wind
2)icy expedition
3)icy frost
4)icy water
In one of the phrases below, the underlined word is WRONGLY used. Find the error and fix it. Write the number of the phrase and the correct word.
1)ice hike
2)icy icicle
3)ice crystal
4)icy crust
In one of the phrases below, the underlined word is WRONGLY used. Find the error and fix it. Write the number of the phrase and the correct word.
1)ice rain
2)icy groats
3)icy chit
4)Icy carnage
In one of the phrases below, the underlined word is WRONGLY used. Find the error and fix it. Write the number of the phrase and the correct word.
1)ice obstruction
2)ice crossing
3)ice sight
4)ice mainland
1) Ice hockey is a sports team game on ice playground with puck and sticks.
2) Lovers of swimming in winter ice water are called walruses.
3)In ice lichens, mosses, polar poppies grow in the zone.
4)Ice the wind blows overhead.
In one of the sentences below, the underlined word is WRONG. Find the error and fix it. Write the sentence number and the correct word.
1) Snow is precipitation in the form icy crystals.
2) Fluffy icy frost covered the branches.
3) "Road of life" - icy road through Ladoga in the winter of 1941-1943.
4) Gerda managed to melt icy Kai's heart
7. ANSWERS
|
test item number |
Phrase or sentence number | |
|
ice |
Ice supplies the planet with a huge amount of fresh water and keeps the global water level in the world's oceans from rising catastrophically.
In addition, ice contains useful information about the past of our planet, and also talks about the future of climate on Earth.
Here are the most Interesting Facts about ice on Earth and beyond:
Ice names
1. Ice has many different names.
Only sea ice has multiple names, not to mention ice in the Arctic and Antarctic. Broken ice, deep water ice, nilas, and pancake ice are just some of what can be found in the Arctic and Antarctica.
If you swim near the north or south pole, then you better know where the iceberg is, and where the foot of the fast ice is (ice fastened to the shore or bottom), what is the difference between a hummock and a hummock, and between a floating ice floe and a floberg (floating mountain) .
But if it seems to you that these words are more than enough for you, then you will be surprised to learn that the Inupiat people of Alaska have 100 different names for ice, which is logical for a people who live in cold places.
freezing rain
2. Freezing rain occurs when snow passes through warm and cold layers of the atmosphere.
Freezing rain can be deadly. This is how it occurs: snow enters the warm layer of the atmosphere and melts into raindrops, then passes through the cold layer of air. Raindrops do not have time to freeze through this cold layer, but when they hit a cold surface, these drops instantly turn into ice.
As a result, a thick layer of ice forms on the roads, and everything around turns into an ice rink. Ice also accumulates on electrical wires, which can lead to their breakage. Ice that has accumulated on the branches can break them off, which is very dangerous for people.
Today there are laboratories where scientists try to predict where and how this rain might strike. One such laboratory is located in New Hampshire, where scientists create simulations of freezing rain.
Dry ice
3. Dry ice is not made up of water.
In fact, this is frozen carbon dioxide, which can change its state from solid to gaseous at room temperature and atmospheric pressure, bypassing the liquid phase. Dry ice is quite useful for keeping some items cold, as it freezes at -78.5 degrees Celsius.
invention of the refrigerator
4. Ice helped people invent the refrigerator.
Thousands of years ago people used ice to keep food fresh. In the 1800s, people cut ice cubes from frozen lakes, brought them back and stored them in special isolated rooms and cellars. By the end of the 19th century, people were using household ice boxes for food, which later turned into refrigerators.
Ice not only made life easier for individual homes, but also played a key role in the mass production and distribution of meat and other perishable foods. All this eventually led to urbanization and the development of many other industries.
By the end of the century pollution environment and mountains of rubbish thrown into sewage have polluted many natural ice reserves. This problem led to the development of the modern electric refrigerator. The very first commercially successful refrigerator was released in 1927 in the USA.
Greenland ice sheet
5. The Greenland ice sheet contains 10% of the world's glacial ice on the planet, and it's melting fast.
This ice sheet is the second largest ice mass in the world after the Antarctic ice sheet, and contains enough water to raise the world's sea level by at least 6 meters. If every glacier and ice sheet on Earth melts, then the water level will rise by more than 80 meters.
Greenland's ice sheet loses 8,000 tons every second, according to a study published in 2016 in the journal Nature Climate Change. Scientists have been studying this ice sheet for several years to better understand how it is responding to climate change on Earth.
Icebergs and glaciers
6. Icebergs and glaciers are not only white.
White light is made up of many colors, and each has its own wavelength. As snow accumulates on the iceberg, the air bubbles in the snow shrink, and more light enters the ice than is reflected from the bubbles and small ice crystals.
This is where the trick comes in: Longer wavelength colors like red and yellow are absorbed by the ice, while shorter wavelength colors like blue and green reflect the light. Therefore, icebergs and glaciers have a bluish-greenish tint.
Ice Ages on Earth
7. There have been many ice ages on Earth.
Often when we hear about an ice age, we think of only one such period. In fact, there were several ice ages on the planet before us, and they were all very severe. Scientists suggest that at some time our planet was completely frozen, and scientists call this hypothesis "Snowball Earth".
There are suggestions that some ice ages were the result of the evolution of new forms of life - plants, as well as unicellular and multicellular organisms - which contributed to a change in the concentration of oxygen and carbon dioxide in the atmosphere so that it led to a change in the greenhouse effect.
The earth will continue to go through cycles of warm and cold periods. However, at this stage, scientists predict that over the next 100 years, the rate of warming will be at least 20 times the rate of previous periods of warming.
fresh water on earth
8. More than 2/3 of the fresh water on Earth is stored in glaciers.
Melting glaciers will lead not only to an increase in the level of the world's oceans, but will also lead to a significant decrease in the level of fresh water reserves and its quality. In addition, the melting of glaciers will lead to a problem of energy supply, since many hydroelectric power plants will not be able to work properly - due to melting, many rivers will change their channels. In some regions such as South America and the Himalayas, these problems are already being felt.
ice planets
9. Ice is not only on Earth.
Water is made up of hydrogen and oxygen, and these elements are abundant in our solar system. Depending on their proximity to the Sun, different planets in our solar system have different volumes of water. For example, Jupiter and Saturn are far from the Sun, and there is much more water on their satellites than on Earth, Mars and Mercury, where due to high temperatures, hydrogen and oxygen find it more difficult to form water molecules.
Europa is a satellite of Jupiter
The distant planets have several frozen satellites, one of which is called Europa - the 6th satellite of Jupiter. This satellite is covered with several layers of ice, the total thickness of which is several kilometers. Cracks and undulations were found on the surface of Europa, which were probably formed by the waves of the underwater ocean.
Enceladus - Satellite of Saturn
The large reserves of water on Europa have led scientists to speculate that it could harbor life.
Ice volcanoes (cryovolcanoes)
10. There is such a thing as ice volcano(cryovolcano)
Enceladus, one of Saturn's moons, boasts one very interesting feature. Its north pole area contains cryovolcanoes, an exotic type of geyser that erupts ice instead of lava.
This happens when ice deep below the surface heats up and turns into steam, after which it erupts into the moon's cold atmosphere as ice particles.
Life on Mars
11. Ice on Mars could help us learn about life on the Red Planet.
According to information from satellites, there is ice on Mars (both dry and in the form of frozen water). This ice is found in the polar caps of the Red Planet and in permafrost regions.
The reserves of ice on Mars may provide an answer to the question, which has been discussed for many years - whether life can be supported on Mars.
In future missions to Mars, scientists will try to find out if the water supply, which may come from underground glaciers, could support life.
Frozen human mummy
12. The best-preserved mummies were frozen.
La Doncella
From the Andes to the Alps, frozen human remains are allowing scientists to learn more about how people lived hundreds and thousands of years ago. One of the best-preserved remains belongs to a 15-year-old boy from the Inca tribe, who was named La Doncella, or the Virgin.
Presumably, the girl was sacrificed about 500 years ago, on top of the Lullaillaco volcano, which is located in Argentina. The girl was found along with other children. It is assumed that she died of hypothermia.
Ötzi
Another frozen mummy - Ötzi - belongs to the Chalcolithic era. This ice mummy of a man was found in 1991 in the Ötztal Alps near the border of Austria with Italy. Presumably the mummies are 5,300 years old.
ice modifications. The phase diagram in the figure on the right shows at what temperatures and pressures some of these modifications exist (more Full description ).The openwork crystal structure of such ice leads to the fact that its density, equal to 916.7 kg / m³ at 0 ° C, is less than the density of water (999.8 kg / m³) at the same temperature. Therefore, water, turning into ice, increases its volume by about 9%. Ice, being lighter than liquid water, forms on the surface of water bodies, which prevents further freezing of water.
The high specific heat of melting of ice, equal to 330 kJ/kg (for comparison, the specific heat of melting of iron is 270 kJ/kg), is an important factor in the circulation of heat on Earth. So, to melt 1 kg of ice or snow, you need as much heat as it takes to heat a liter of water by 80 °C.
Ice occurs in nature in the form of ice proper (mainland, floating, underground), as well as in the form of snow, hoarfrost, frost. Under the influence of its own weight, ice acquires plastic properties and fluidity.
Natural ice is usually much purer than water, since when water crystallizes, water molecules are the first to enter the lattice (see zone melting). Ice may contain mechanical impurities - solid particles, droplets of concentrated solutions, gas bubbles. The presence of salt crystals and brine droplets explains the brackishness of sea ice.
On the ground
The total ice reserves on Earth are about 30 million km³. The main ice reserves on Earth are concentrated in the polar caps (mainly in Antarctica, where the thickness of the ice layer reaches 4 km).
In the ocean
The water in the world's oceans is salty and this prevents the formation of ice, so ice forms only in polar and subpolar latitudes, where winters are long and very cold. Some shallow seas located in the temperate zone freeze over. Distinguish between annual and multi-year ice. Sea ice can be immobile, if connected to land, or floating, that is, drifting. In the ocean there are ices that have broken away from
Around -1.8°C.
The assessment of the amount (density) of sea ice is given in points - from 0 ( pure water) up to 10 (solid ice).
Properties
The most important properties of sea ice are porosity and salinity, which determine its density (from 0.85 to 0.94 g/cm³). Due to the low density of ice, ice floes rise above the surface of the water by 1/7 - 1/10 of their thickness. The melting of sea ice begins at temperatures above −2.3°C. Compared to freshwater, it is more difficult to break into pieces and is more elastic.
Salinity
Density
Sea ice is a complex physical body consisting of fresh ice crystals, brine, air bubbles and various impurities. The ratio of the components depends on the conditions of ice formation and subsequent ice processes and affects the average ice density. So, the presence of air bubbles ( porosity) significantly reduces the density of ice. The salinity of ice has less of an effect on density than does porosity. With an ice salinity of 2 ppm and zero porosity, the ice density is 922 kilograms per cubic meter, and with a porosity of 6 percent it drops to 867. At the same time, with zero porosity, an increase in salinity from 2 to 6 ppm leads to an increase in ice density only from 922 to 928 kilograms per cubic meter.
Thermophysical properties
Shades of color of sea ice in large massifs vary from white to brown.
white ice formed from snow and has many air bubbles or brine cells.
Young sea ice of a granular structure with significant amounts of air and brine often has green color.
Multi-year hummocky ice, from which impurities have been squeezed out, and young ice that froze under calm conditions often have blue or blue color. Glacial ice and icebergs are also blue. V blue ice the acicular structure of the crystals is clearly visible.
Brown or yellowish ice has a river or coastal genesis, it contains impurities of clay or humic acids.
The initial types of ice (ice fat, sludge) have dark grey color, sometimes with a steel tint. As the thickness of the ice increases, its color becomes lighter, gradually turning into white. When melting, thin pieces of ice turn gray again.
If the ice contains a large number of mineral or organic impurities (plankton, eolian suspensions, bacteria), its color may change to red, pink, yellow, up to black.
Due to the property of ice to trap long-wave radiation, it is able to create a greenhouse effect, which leads to heating of the water under it.
Mechanical properties
Under the mechanical properties of ice understand its ability to resist deformation.
Typical types of ice deformation: tension, compression, shear, bending. There are three stages of ice deformation: elastic, elastic-plastic, destruction stage. Accounting for the mechanical properties of ice is important in determining the optimal course of icebreakers, as well as when placing cargo on ice floes, polar stations, and when calculating the strength of the ship's hull.
Conditions of education
When sea ice forms, tiny droplets of salt water are trapped between entirely fresh ice crystals, which gradually flow down. The freezing point and temperature of the greatest density of sea water depends on its salinity. Sea water, the salinity of which is below 24.695 ppm (the so-called brackish water), when cooled, first reaches the highest density, like fresh water, and with further cooling and no mixing, it quickly reaches the freezing point. If the salinity of the water is higher than 24.695 ppm (salt water), it cools to the freezing point with a constant increase in density with continuous mixing (exchange between the upper cold and lower warmer layers of water), which does not create conditions for rapid cooling and freezing of water, that is, when Under the same weather conditions, salty ocean water freezes later than brackish water.
Classifications
Sea ice in its own way location and mobility divided into three types:
- floating (drifting) ice,
According to the stages of ice development there are several so-called initial types of ice (in order of formation time):
- intra-water (including bottom or anchor), formed at a certain depth and objects in the water under conditions of turbulent mixing of water.
Further in time of formation types of ice - nilas ice:
- nilas, formed at a calm sea surface from lard and snow (dark nilas up to 5 cm thick, light nilas up to 10 cm thick) - a thin elastic crust of ice that easily bends on water or swell and forms jagged layers when compressed;
- bottles formed in freshened water with a calm sea (mainly in bays, near river mouths) - a fragile, shiny crust of ice that easily breaks under the influence of waves and wind;
- pancake ice, formed during weak waves from ice fat, slush or sludge, or as a result of a break as a result of the waves of a bottle, nilas or the so-called young ice. It is a plate of ice of a rounded shape from 30 cm to 3 m in diameter and 10-15 cm thick with raised edges due to rubbing and impacts of ice floes.
A further stage in the development of ice formation are young ice, which are subdivided into gray (10-15 cm thick) and gray-white (15-30 cm thick) ice.
Sea ice that develops from young ice and is no more than one winter period old is called first year ice. This first-year ice can be:
- thin first-year ice - white ice 30-70 cm thick,
- medium thickness - 70-120 cm,
- thick one-year ice - more than 120 cm thick.
If sea ice has been melted for at least one year, it is classified as old ice. Old ice is divided into:
- residual one-year - ice that has not melted in summer, which is again in the freezing stage,
- two-year - lasted more than one year (thickness reaches 2 m),
- multi-year - old ice with a thickness of 3 m or more, which has melted for at least two years. The surface of such ice is covered with numerous irregularities, mounds, formed as a result of repeated melting. bottom surface multi-year ice also differs in great unevenness and variety of form.
Thickness of multi-year ice in
