River Ice
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Ice formation in rivers is a complex process. It is more complex than lake ice in its development. Mainly because of the way the water velocity and turbulence of the water flow. In lakes, the surface temperature drops in response to cooling by the air above. The turbulent mixing in rivers causes the water depth to cool uniformly even after its temperature has fallen below the temperature of maximum density (4° C, or 39° F). This is where all known substances undergo thermal expansion in response to heat.

Once the water temperature drops to the freezing point and further cooling occurs, it will fall below freezing in a process known as supercooling. Ice particles from the air cause further ice nucleation in the flow. This initial process forms a crystal from a solution, a liquid, or a vapor. Then, the water temperature returns to the freezing point. Ice production then matches the cooling rate occurring at the surface.

The supercooling of river water allows ice particles to stick to one another since ice particles are unstable and actively grow in supercooled water. They stick to each other by freezing when they touch surfaces and other particles cooled below the freezing point. In rivers and streams, frazil particles can stick to the bottom of the water and build up a loose, porous layer known as anchor ice. The particles will not stick to one another if the water temperature rises above freezing. Anchor ice usually forms on the bottom of shallow streams at night, when cooling occurs, and is only released under the influence of air temperature and solar radiation.

Temperature and turbulence are the two most essential factors determining how ice forms. Temperature is controlled by climate, and turbulence is affected by the size of the water body and the materials that make up that water body. Turbulence in streams is driven by the speed of water and the kinds of materials forming the stream’s channel. Bumpy materials result in more turbulence. Turbulence can also be high in large lakes when the wind can blow over the water surface for large distances and create waves and currents.

The first particles of ice in the water flow are called frazil ice. Or P3 (Primary 3). P3 ice forms in rivers with enough turbulence to mix the supercooled water to much deeper depths, often to the bottom. The turbulence is effective at removing heat from growing crystals. These particles are typically about 1 millimeter (0.04 inch) or smaller in size and usually in the shape of thin disks. Frazil appears in several types of initial ice formation in several different forms. This can include thin, sheetlike formations, ice particles that appear in larger masses, and ice particles that exhibit a slush-like appearance on the water surface.

Frazil Ice forms into pans on the surface of rivers. It is also a prevalent ice type found throughout all ice formations. These pans merge and freeze to form larger floes(a sheet of floating ice) or gather at the leading edge of an ice cover, forming an ice layer that progresses upstream. The thickness of the ice depends on the velocity of the river flow. The forces exerted by the water flow and its weight acting in the downstream direction will thicken the ice by shoving it.

As the ice cover accumulates and progresses upstream, it adds resistance to the flow and displaces water. These effects cause the river's depth to be greater upstream, reducing the velocity and enabling further upstream progression of the ice. This phenomenon is called staging by its effect of increasing the water level or “stage.”

Example of Staging: https://www.britannica.com/science/staging-ice-formation
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Once the first ice cover has formed, columnar crystals grow into the water below, forming a smooth bottom surface. An exception to this arises when above-freezing water flows beneath the ice cover. When this occurs, the moving water either causes the undersurface to melt or reshape. In some rivers, fixed ice formation occurs along the shorelines. The shore ice then gradually widens from the shoreline.

In deeper rivers, frazil produced upstream can be carried downstream and transported beneath fixed ice covers, where it may be deposited and form accumulations of ice called hanging dams. These deposits may block portions of the river’s flow. Ice formations in smaller, shallower streams may be combinations of shore ice, anchor ice deposits, small hanging dam-like accumulations, and sheet ice.

Ice in smaller streams shows more variation through the winter since most of the water comes from groundwater inflows during periods of rain. Groundwater is warm and, over time, melts the ice formed during freezing periods. At other times, it forms large ice buildups. These are called icings, Aufeis, or naleds.

As winter progresses and air temperatures rise above the freezing point, river ice melts from the heat from above and the action of the warm water flowing beneath. The turbulent water on the undersurface causes a melting pattern as the waves become oriented crosswise to the current direction. This is a standard process for both deep and shallow rivers.

During the spring periods of midwinter, thaw causes additional runoff from snowmelt and rain and increases the flow in the river. The increased flow raises the water level and breaks the ice loose from the banks. It also increases the forces exerted on the ice cover. If these forces exceed the strength of the ice, the cover will move, break up, and be transported downstream. In some places, the quantity of ice will exceed the river's capacity, and an ice jam will form. The jam may then raise the water level and cause flooding. Rivers also break up in response to runoff from snowmelt or rain.


Sea Ice
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Sea ice is where things get tricky, as salt becomes an additive factor. Sea ice and ocean ice go hand in hand, as each body of water contains salt and flows in and out of the other.

Sea ice grows and melts in salty ocean water, which sets it apart from icebergs, glaciers, lakes, and river ice. Icebergs and glaciers form from snow falling on land, while lake and river ice form from fresh water. Lake ice tends to freeze as a smooth layer, while sea ice develops into various shapes because of the turbulence of ocean water. Sea ice is vital for several reasons: it is an essential habitat for many species, protects coasts from erosion by acting as a barrier against storms and waves, and sustains Arctic Inuit populations, who depend on it for hunting, livestock farming, and fishing.

As sea ice crystals form, the salt is excluded. Sea ice contains much less salt than seawater. The older the sea ice, the lower its salt concentration. Sea ice loses its salt content over time. About 20% of the salt remains trapped in pockets of water between the ice crystals. As ice forms and the salt is excluded, the salinity of the remaining water increases. These unfrozen pockets of salty water make sea ice softer and slushy than freshwater ice, which is rigid. Sea ice is not uniformly smooth but is a surface that varies dramatically across short distances. Most sea ice features occur when sea ice either converges or spreads out.

Sea ice does not generally grow and melts in a single place. Instead, it is constantly moving and changing location. Only in places near the coast, where ice can attach to the coast or shallow shelf region, is it pinned in place and does not move.

Seawater begins to freeze at about –1.8 C, a lower temperature than fresh water. Ice formation begins at the surface with tiny needle-like ice crystals called frazil, which accumulate and make the water appear slushy and cloudy.

When frazil forms, highly saline water accumulates into brine droplets, typically expelled back into the ocean. The salinity of the surface water then rises. Some brine droplets become trapped in pockets between the ice crystals. The brine remains liquid because much cooler temperatures would require it to freeze. At this stage, the sea ice has a high salt content.
However, Over time, the brine drains out, leaving air pockets, and the salinity of the sea ice decreases. This stage is called grease ice. In calmer water, these tiny crystals can freeze together into a thin surface layer called nilas, reaching a thickness of up to 10 cm.

Wave action can break up the nilas into small pieces. These bump into each other and form rounded shapes with raised edges, called pancake ice. If temperatures remain cold, the pancake ice freezes into solid ice floes, hard surfaces covering the ocean. Ice floes then freeze together into ice fields.

Wind, ocean currents, and other forces push sea ice around, ice floes collide, and ice piles into ridges and keels. Ridges are small “mountain ranges” that form on top of the ice; keels are the corresponding features on the underside of the ice. The total thickness of the ridges and keels can be several meters, and the surface ridges can easily be 2 meters or higher.

Ridges: https://en.wikipedia.org/wiki/Pressure_ridge_(ice)
Sea Ice Keel: https://www.researchgate.net/figure/Sea-ice-keel-left-and-iceberg-keel-right_fig63_334458575
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Ridges are blocky with very sharp edges. Over time, during the summer melt, the ridges erode into smaller, smoother “hills” of ice called hummocks. This process is similar to the erosion of mountain peaks into smooth, rolling hills but at an accelerated pace. When keels erode into smooth features, they are called bummocks.

Once ice floes form, the water underneath becomes insulated, and heat loss to the atmosphere declines, so the water no longer cools, and no more ice formation occurs. Young sea ice is usually relatively thin, not more than 3-4 m thick. The ice can get thicker through precipitation, but due to the low temperatures, whatever does occur tends to accumulate. The accumulated ice and snow add to the overall thickness of the sea ice.

During the ice formation, Brine moves out of sea ice in various ways. Brine (or salted water) is water with a high-concentration salt solution. The brine migrates downward through holes and channels in the ice and empties back into the ocean. The other way is that the ice will compress surrounding the brine and break the brine pockets, allowing the brine to escape to the ocean.

The sea ice melts throughout the seasons, especially during the summer, forming small freshwater ponds called melt ponds. This freshwater travels through the cracks and holes in the ice, washing away the remaining brine. When the sea ice surface cools, brine increases in salinity to the point where it can melt the undersides of the existing ice. This leads to a downward brine migration, allowing the substance to escape into the ocean below the ice sheet.

When large sheets of sea ice are formed, they exist in two forms: fast or land-fast ice. Land-fast ice refers to the large, solid ice sheets attached to land. Pack ice consists of smaller, free-floating pieces of sea ice. They either formed independently or broke off from fast ice.

Pack ice is also subject to the currents flowing underneath, and the ice sheets are constantly moving, breaking up, or being pushed together. When pieces of ice converge, they buckle and crack or override one another as convergent lithospheric plate boundaries. These collisions can create tall, jagged pressure ridges that extend for several kilometers.

Pack Ice: https://www.britannica.com/science/pack-ice
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Snow also plays a massive role in regulating sea ice formations. Snow covers sea ice and insulates it. The insulation slows ice growth in the winter and delays melting in the summer. The snow is usually dry and hard-packed. If snow cover is thick, over-thin sea ice, the weight of the snow can push the ice down into the water below. The salty ocean water will flood the snow, creating a slushy layer. This flooded sea ice is more common in the Antarctic than in the Arctic because Antarctica has thinner ice and more snowfall.

During summer, as the snow on top of sea ice melts, the meltwater accumulates in depressions on the sea ice surface called melt ponds. These ponds absorb more heat from sunlight than the surrounding sea ice and grow in area and depth. The fresh water in melt ponds appears blue because light reflects and scatters off the sea ice surface from the bottoms and sides of the melt pond. If a pond melts through the entire thickness of the ice, the pond's color turns dark, like the ocean. Melt ponds are more common in the Arctic than in the Antarctic because Arctic ice lasts longer and Arctic sea ice has an uneven surface, giving melt ponds places to form.

Features on sea ice's surface include frost flowers and ice crystals deposited when water vapor bypasses the liquid phase and becomes a solid. Frost flowers roughen the surface and alter its electromagnetic signal.

Frost Flowers: https://en.wikipedia.org/wiki/Frost_flower_(sea_ice)
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Sea ice has an albedo than many other Earth surfaces. Albedo is a quantity that indicates how well a surface reflects solar energy. Albedo is measured in values between 0 and 1. Albedo commonly refers to the “whiteness” of a surface, with 0 meaning black and 1 meaning white. A value of 0 means the surface is a “perfect absorber” that absorbs all incoming energy. A value of 1 means the surface is a “perfect reflector” that reflects all incoming energy. An ocean albedo is approximately 0.06, while bare sea ice varies from 0.5 to 0.7. This means the ocean reflects only 6 percent of the incoming solar radiation and absorbs the rest, while sea ice reflects 50 to 70 percent of the incoming energy.

The sea ice absorbs less solar energy and keeps the surface cooler. Snow has a higher albedo than sea ice. Thick snow-covered sea ice reflects as much as 90 percent of the incoming solar radiation. This insulates the sea ice, maintaining cold temperatures and delaying ice melt in the summer. After the snow starts to melt, melt ponds may form. As the melt ponds grow and deepen, the albedo decreases, leading to higher absorption of solar radiation and an increased melting rate.

Sea ice growth mainly starts in autumn when incoming solar energy decreases, and air temperatures fall below freezing. Ice growth continues through the winter, and the ice becomes thicker as heat transfers from warm oceans to the cold atmosphere. Sea ice is continually in motion, except in coastal regions where ice grows out from and stays attached to the shore like fast ice. The motion of ice results from a balance of forces defined by Newton's Second Law, which states that force equals mass times acceleration.

Sea ice is classified by stages of development related to thickness and age. The classification process categorizes sea ice into two primary age groups: first-year and multiyear. The seawater ice process starts in an icey, dense, salty water stage that leaks from the ice and sinks. This brine is “supercooled”; it is cooled below the usual freezing point of seawater but remains liquid due to the salt content. Sheets of sea ice form when frazil crystals float to the surface, accumulate, and bond together. This process often expels salty water in “brine pockets.” When supercooled brine comes into contact with the surrounding water, it causes the water around it to freeze, creating ice stalactites, or “brinicles,” that can be several meters long, and the brinicle grows downwards.

First-year sea ice forms in winter, when temperatures are at their lowest. When temperatures rise, the seasonal sea ice melts in a process known as the breakup. First-year sea ice is about 1 to 2 meters thick. There is also multiyear sea ice that does not melt yearly and can be several meters thick.

Multiyear ice has distinct properties that distinguish it from first-year ice. It contains much less brine and more air pockets than first-year ice, which means “stiffer” ice. Less brine also means that multiyear ice is much fresher, containing minimal salt. Multiyear ice often supplies the freshwater needed for polar expeditions.

Multiyear ice is more common in the Arctic than in the Antarctic. Ocean currents and atmospheric circulation move sea ice around Antarctica, causing most ice to melt in the summer. Most of the multiyear ice that does occur in the Antarctic persists because of a circulating current in the Weddell Sea on the eastern side of the Antarctic Peninsula.

Multiyear ice has declined significantly in the Arctic in recent times. The first major complete recording of ice flow began in 1984. The first substantial drop in multiyear ice occurred from the late 1980s through about 1995. The leading cause was a positive Arctic Oscillation, which set up a wind circulation pattern that pushed multiyear ice out of the Arctic from the Beaufort Sea region through Fram Strait, east of Greenland. From 2007 to 2023, multiyear ice has remained lower than pre-2005 levels, and the overall trend is downward due to global warming.

Five principal forces act on sea ice. The first one is the most important: wind. Wind is the primary force responsible for ice motion, particularly on the timescale of days or weeks. Wind blowing on the top surface of the sea ice results in a drag force on the ice surface, which causes the ice to drift. The amount of the force depends on the speed of the wind and the characteristics of the sea ice surface. The wind affects rough ice surfaces more than smooth surfaces.

The next is ocean currents. An ocean current force acts opposite to the wind force and drags on wind-driven sea ice motion. Currents are essential in longer-term ice motion.

The Coriolis force causes objects to accelerate because of Earth's rotation. The Coriolis force is small at scales of tens to hundreds of kilometers, but it does affect processes that occur at the global scale, such as ocean currents, winds, and ice motion. In the Northern Hemisphere, the Coriolis force causes objects to deflect to the right, and in the Southern Hemisphere, objects deflect to the left. The Coriolis force barely exists at the equator, and because the force increases toward the poles, it plays a vital role in determining sea ice motion.

Internal ice stress measures the strength of the ice. Like the ocean current force, internal ice stress usually acts as a resistance to the motion caused by the wind force. Under circumstances when the sea ice pack is loosely compacted and can flow freely, the internal ice stress is minimal. When the ice is compact and cannot flow, the internal ice stress can be high. For example, ice motion is significant with a strong onshore wind. If the strong wind pushes thick, compact ice toward a shore, there may be little or no motion because the ice has nowhere to go.

Internal ice stress is also vital in deformation and features, such as ridges and leads. Sea ice is susceptible to tension forces. When the ice is “pulled apart” by winds or currents from opposite directions, the ice easily fractures and forms lead. Sea ice is also much stronger under compression forces. When the ice is pushed together by converging winds or currents, the internal ice stress keeps the ice from moving together, but if the ice is pushed together hard enough, the ice will “fail,” or break apart, and pile up into ridges.

The strength of ice depends primarily on its thickness. Thin ice breaks apart easily under compression, while thick ice is much stronger. The formation of ridges can create piles of sea ice many meters thick. Internal ice stress also depends on brine content, temperature, density, and other factors.

The relationship between thermodynamics and sea ice thickness is related to freezing degree days (FDD), which measure how cold it has been for how long. The cumulative FDD is simply the daily degrees below freezing summed over the days the temperature was below freezing.

Ice thickness increases at a rate roughly proportional to the square root of the cumulative FDD. Snow cover dramatically alters sea ice thickness. Snow is an effective insulator, slowing heat transfer from the ocean through the ice and to the atmosphere. Because of this, snow essentially slows the growth of ice.

Sea-surface tilt can also have a noticeable effect on sea-ice motion. The ocean surface is not perfectly flat. Even if the ocean were completely still, it would consist of high and low regions caused by slight differences in gravity. This undulating surface is called a geoid. Because the ocean is never at rest, the surface is higher than the geoid in some regions and lower in others.

Several factors contribute to ocean surface-level differences, including uneven heating, salinity variations, and currents. Differences in surface level result in sea-surface tilt, a force that influences ice motion.

Another thing to note is that Antarctic large-scale sea ice circulation is generally clockwise around Antarctica. There is also an average northward component, so sea ice gradually moves towards the northern ice edge after it forms. Compared to the Arctic, the Antarctic has no surrounding land boundary for the northward-flowing sea ice to run into, so the ice flows northward until it melts in warmer oceans and air temperatures.


Ocean Ice
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Similar to Sea Ice, As ocean water freezes, it forms frazil. Because salt does not freeze, the crystals expel salt into the water, and frazil crystals consist of fresh water. In calm waters, frazil crystals form smooth, thin ice, called grease ice, for its resemblance to oil slicks. This is the same process that occurs in sea ice.

In rough ocean waters, ocean frazil crystals also accumulate into pancake ice; if the motion is strong enough, thin sheets of ice slide over one another in a process known as rafting. If the ice is thick enough, ridging occurs, where the sea ice bends or fractures and piles on top of itself. Each ridge consists of above-the-surface ice, called a sail, and keels. Because of the difference in density between the ice and the water, most of the ice in a ridge is below the surface. Keels are about nine times thicker than sails. In the Arctic, ridges up to 20 meters (66 feet) thick can form when thick ice deforms.
Like sea ice, the salinity of the water is essential to the freezing process. Salinity is a measurement of the concentration of dissolved salts in water. A common way to define salinity values is now c described in practical salinity units (PSU). The average salinity of the ocean typically varies from 32 to 37 PSU, but in polar regions, it is less than 30 PSU. Sodium chloride (table salt) is the most abundant of the many salts found in the ocean.

Fresh water freezes at 0°C (32°F), but the freezing point of seawater varies. The Arctic Ocean is generally fresher than other oceans, somewhere between 30 and 34 PSU, but salinity levels vary by region, and areas with solid river inflow have even lower salinity.

Now, for some ocean ice characteristics, we will start with leads.

Leads are narrow, linear cracks in the ice that form when ice floes diverge or shear as they move parallel in oceans. The formation of leads is similar to mid-ocean ridges or shear zones that form from Earth's moving tectonic plates. The width of leads varies from a couple of meters to over a kilometer. Leads can often intersect, creating a complex network of linear ice features extending over hundreds of kilometers.

Leads are much darker than surrounding ice, which, during the summer, results in a lower ability to reflect light. Lower reflectivity leads it to absorb more solar energy than the surrounding ocean, which heats the water in the leads and speeds up the melting of surrounding ice. In summer, leads remain open and expand or close if winds and ocean currents push the surrounding ice together. Leads forming in winter will generally start to refreeze very quickly, and this refreezing process adds salt to the open ocean layer. While the lead remains open in winter, it releases heat and moisture into the atmosphere. Leads are also crucial for wildlife. Seals, whales, penguins, and other animals rely on leads for access to oxygen. Polar bears in the Arctic often hunt near leads because they know their prey will likely come to the surface to breathe in such areas.

Lead Ice: https://en.wikipedia.org/wiki/Lead_(sea_ice)
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Another characteristic of ocean ice is that of Polynyas. Polynyas exist both in oceans and in seas. They are persistent open-water areas, oval or circular holes where the water remains open because of processes that prevent sea ice from forming or quickly moving out of the region. There are two types of polynyas, open and coastal polynyas, which are classified by their various mechanisms of ice reduction.

Sensible-heat (open-ocean) polynyas happen when heat transfer occurs between two bodies at different temperatures that are in contact with each other. The body with the higher temperature transports sensible heat to the body with the lower temperature. A sensible-heat polynya forms when water above freezing upwells or moves from the ocean's lower depths to the surface. Heat transfers from the warmer water to the ice, melting it and preventing new ice from forming. The topography of the ocean bottom or overturning of water causes the warm water to rise to the surface. Sensible-heat polynyas usually form in mid-ocean areas.
Polynyas: https://mallemaroking.org/amundsen-sea-polynya/

Latent-heat (coastal) polynyas have heat transfer that occurs when their matter changes state. Latent heat is absorbed when ice melts and released into the surroundings when liquid water freezes. The process is called “latent” because it is not associated with a temperature change but a state change.

A latent-heat polynya is characterized by ocean water when it reaches its freezing point. It forms due to persistent winds pushing the ice away from a barrier, such as a coast, fast ice, a grounded iceberg, or an ice shelf. As new ice grows within polynyas, the wind blows it to the leeward side while the windward side remains ice-free. Latent heat is released as water freezes and evaporates into the air.

Polynyas are essential for the ecosystem. Like leads, they are a source of heat and moisture to the atmosphere, so they modify the weather in surrounding areas. Polynyas are also essential resources for wildlife. They provide various animals with access to the ocean and the atmosphere. Because polynyas persist for extended periods than leads and overturning ocean water brings nutrients to the surface, phytoplankton thrive in polynyas. Phytoplankton are microscopic plant-like organisms that form the basis of the marine food chain. During the summer, Antarctic polynyas are one of the most biologically productive regions in the world's oceans.


Lake Ice
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Now, let’s be less salty and move back to freshwater processes.

Lake water contains many small particles, including suspended sediment and bacteria. Ice mainly forms when the water gets supercooled from a few hundredths of a degree to a couple of degrees. Once the ice is in still water, it propagates through the supercooled water at the surface as blade-like crystals. The growth rate is controlled by the water's supercooling and the rate at which it can be conducted and radiated into the air from the top surface of the ice crystals.

The initial ice sheet or Primary Ice formation in lakes happens in quiet water with moderate temperatures. Under calm conditions, ice freezes on lakes very similarly to how it freezes in an ice-cube tray. Lake ice freezes first at the surface, starting at the edges or shoreline. Water near the shore is typically shallower and contains less heat than deeper water, so it can reach the freezing point faster than deeper water. The blades grow across the water until they run into each other. After that, dendrites (ice branches on branches) grow off the blades to fill the remaining water surface between the needles. The blades stay on the surface because they float where the supercooled water is. In good conditions, the layer is thin, and supercooling is low. The resulting ice will range from a few inches to several feet.

Warm water gets denser as it gets colder and sinks. Water Colder than 4° Celsius begins expanding and becomes less dense as it gets colder. As a result, when it becomes close to freezing, colder water floats to the top, and warmer water sinks to the bottom. The coldest water, which floats to the top of the lake in wintry conditions, freezes to form a layer of ice. When the water freezes to ice, the ice becomes significantly less dense than the water and continues to float on the lake's surface. Because the crystal lattice allows much light to pass, aquatic algae and plants can grow under lake ice.

Once the primary ice sheet has formed, supercooled water can form under it, except when it is very close to the ice. Ice sheet thickening is limited mainly by how fast heat can be conducted away from the bottom of the sheet. S1 (Secondary) ice is often called 'large-grain ice.' P2 (Primary 2) Ice forms on still water if the air is cold.

P4 (Primary 4) ice is formed when snow falls into the water, ready to freeze, creating closely spaced formation sites and having a small grain size. This is different from frozen shush, formed when snow falls on top of an ice sheet and then gets saturated with water through cracks and holes in the ice sheet. This is called 'snow-ice,' a common form of superimposed ice (T1).

Ice formation on lakes and ponds that are not affected by snow falling; rather, wind and waves, needles, and flakes form on the surface. Collisions and wave action break them up, and they can become tangled up with each other and form small rafts of several flakes. This creates many nucleation sites and allows the primary needles and branches to grow into each other a short distance away, keeping the crystal size small. This ice can evolve in different ways depending on the lake's size, the proximity to the downwind shore, the amount of wind, and other factors.

Grain size is established in the thin primary ice layer; the general texture is preserved as the secondary ice grows on the bottom of the ice sheet. The formation process is called 'slow growth.' The growth rate is controlled by the rate at which latent heat can be conducted through the ice and into the air. This results in a relatively smooth bottom on the ice sheet and a uniform ice growth rate, assuming there is no snow on the ice. Grain size increases toward the bottom of the ice sheet.

Water pressure also plays a role in deep lakes. The gravitational weight of all the water higher up in the lake presses down on the water located deeper. The pressure allows the water near the bottom of the lake to get cold without expanding and rising. Because of the pressure, the water at the bottom of deep lakes can become cold without freezing to ice.

Another characteristic of lake ice is drifting ice; drifting ice is called “pack ice” and comprises sheets of floating ice called floes separated by water. When floes are pushed together, when one floe moves on top of another, this is called “rafting.” When sheets of regular, flat lake ice are broken and pile up, this is called “hummocked ice.” Hummocked ice occurs along shores exposed to wind, pushing soils and material inland. This ice push is called ice ride-up, surge, or ramping.



Glaciers and Icebergs
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Glaciers
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Glaciers form on land and are classified by size. In Antarctica, glaciers can sometimes expand into ice platforms, part of which rests on the bedrock while parts float into the sea. The floating part is called an ice shelf. Ice shelves can cover several thousand square kilometers and reach heights of several dozen meters, creating vertical cliffs several dozen meters high.

Glaciers worldwide are shrinking in size. The worldwide shrinkage of mountain glaciers is thought to be caused by a temperature increase since the Little Ice Age, which ended in the latter half of the 19th century, and increased greenhouse gas emissions.

Water in ice caps and glaciers affects other aspects of the water cycle, such as the weather and the climate. Their Ice is very white, and since white reflects sunlight and heat, large ice fields can determine weather patterns. Air temperatures can be higher a mile above ice caps than at the surface, and wind patterns affecting weather systems can be dramatic around ice-covered landscapes.

The amount of water locked up in glaciers and ice caps is a small percentage of all water on Earth, but it represents a large percentage of the world's total freshwater. The amount of water locked up in ice and snow is only about 1.7 percent of all water on Earth, but the majority of total freshwater on Earth, about 68.7 percent, is held in ice caps and glaciers.

A glacier cave is a cave formed within the ice of a glacier. Although glacier caves are often called ice caves, the term is properly used to describe bedrock caves that contain year-round ice.

Most glacier caves are formed by water running through or under the glacier. This water often originates on the glacier's surface through melting, enters the ice at a moulin, and exits at the glacier's snout at base level. A moulin is a vertical well-like shaft formed where a surface melt stream exploits a weakness in the ice. Heat transfer from the water can cause sufficient melting to create an air-filled cavity.

Some glacier caves are formed by geothermal heat from volcanic vents or hot springs beneath the ice. One of these is the Kverkfjöll glacier cave in the Vatnajökull glacier in Iceland, measured in the 1980s at 2.8 kilometers long and with a vertical range of 525 meters. Some glacier caves are unstable due to melting and glacial motion and are subject to collapse and elimination by global warming. The study of glacier caves itself is sometimes called "glaciospeleology."

Mount Rainier (Washington, US): https://www.mountainguides.com/pop_news_npca-rainier-ice-caves.shtml
Perito Moreno Glacier (Argentina): https://www.manvsglobe.com/perito-moreno-glacier-patagonia-argentina-calafate/
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Titlis (Switzerland): https://www.titlis.ch/en/activities/glacier-cave
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Icebergs
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Icebergs form the edge of glaciers. They are blocks of ice that break away from glaciers and drift out to sea. The process of an ice chunk breaking away from a glacier to form an iceberg is called calving. The visible ‘tip of the iceberg’ typically only represents 20% of the total surface area of the ice block. Icebergs drifting in the ocean can take years to disintegrate before disappearing completely.

Tabular icebergs result from ice breaking off an ice platform and floating in the ocean. They have flat tops and are several hundred kilometers long.

Icebergs: https://www.newfoundlandlabrador.com/trip-ideas/travel-stories/famous-icebergs-of-newfoundland-and-labrador

Tabular icebergs: https://www.nationalgeographic.com/environment/article/this-iceberg-is-perfectly-rectangular-explained
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