Antarctica Glossary of terms I - Z

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ice age (glacial period) - Periods in the Earth's history when the climate was colder and glaciers expanded to cover large areas of the Earth's surface. Ice ages have come and gone many times and will probably continue to do so.

ice blink - A brightness on the horizon, showing in the clouds above it caused by reflection of sunlight from sea ice even in overcast conditions, such a sight is often called an "ice sky". Conversely, a darkness on the horizon when surrounded by ice denotes the presence of open water and is called a "water sky".

ice cap - A large dome-shaped mass of ice that is thick enough to cover all the landscape beneath it so appearing as a smooth coating of ice. Ice caps are smaller than ice sheets, usually under 50,000 square kilometres (19,000 square miles). Ice caps can deform and flow with gravity and spread outward in all directions. Freshwater.

ice cliff - Walls of ice where glaciers meet the sea. Ice cliffs occur because icebergs calve from the front of them giving a continually breaking edge the full height of the glacier. Freshwater.

ice crystals - Tiny particles of ice that grow on all surfaces when the air is supersaturated with water (cold air doesn't hold much moisture so ice crystals are readily formed in Antarctica). Ice crystals account for the majority of the accumulation of glacial ice on the Polar Plateau. They may also be referred to as ice needles, even though they are not needle shaped. Freshwater.

ice floe - A large, flat, sheet of sea ice that has broken off contact with the coast where it was formed and is floating in open water. Sea-water.

ice foot - A "shelf" of ice that forms around many Antarctic shores in the winter time. Sometimes formed by sea spray, often formed where sea-ice joins the land, as the tide rises and falls, a layer of ice is deposited which builds up. Once the sea ice blows out in the spring a distinct ledge several feet high is left behind that can be difficult to cross for men and also for animals. Sea-water

ice sheet - A large mass of ice that is thick enough to cover the landscape beneath it so appearing as a smooth coating of ice. Ice sheets can deform and move with gravity, they are larger than ice caps. Ice sheets cover much of Greenland and Antarctica. Freshwater.

ice shelf - A large flat-topped sheet of ice that is attached to land along one side and floats in the sea or a lake. Formed where a glacier or ice shelf has reached the water and kept flowing, it is fed from the landward side and eroded from the seaward side by the calving of icebergs and melting. Freshwater.

ice stream - A rapidly moving current of ice in an ice sheet or ice cap. Ice streams flow more quickly than the surrounding ice and remove ice from the ice sheet. Antarctic ice streams may flow about one kilometre per year (0.6 miles per year). Freshwater.

ice tongue - A long, narrow, projection of ice out from the coastline, similar in origin to an ice shelf, but usually formed where a valley glacier flows rapidly to the sea or a lake. Freshwater.

iceberg - A large piece of floating ice that has calved, or broken off, a glacier or ice shelf. Icebergs occur in lakes and the ocean and can be vast, the size of islands or small countries. Freshwater.

ionosphere - The electrically-charged layer of the atmosphere that extends from 80 to 400 kilometres (50 to 250 miles) above the Earth's surface. The ionosphere absorbs much of the short wave-length radiation from the sun. As the radiation passes through the ionosphere, it interacts with nitrogen molecules and oxygen atoms. These molecules and atoms absorb the radiation, but in the process they lose an electron (a negatively charged particle) and become a positively charged ion. The ionosphere is where auroras originate.

katabatic winds - Wind that results from dense, cold air flowing down a slope by gravity. Over Antarctica, air cools over the high plateau region and flows towards the coast, by the time it gets to the coast it can have reached extreme speeds and blow continuously for weeks.


land-based ice sheet - a large body of ice with a base mostly above sea level. The East Antarctic Ice Sheet is a land-based ice sheet. Freshwater.

lapse rate - The change in temperature associated with a change in elevation. When climbing a mountain, the temperature falls approximately 1°C for every 100m in altitude gained.

latitude - Imaginary lines that allow for the measurement of position north or south of the equator. Latitude is measured in degrees (one degree - 60 nautical miles, or 111 kilometres). The equator is at a latitude of 0° and the poles lie at latitudes of 90° north (North Pole) or 90° south (South Pole). Lines of latitude differ in length according to how far north and south they are.

lead - Long, narrow opening or fracture in sea ice. Leads can be useful to shipping because they do not have to waste fuel and time by breaking ice, they can be disastrous if travelling over sea-ice as the path is no longer there. Leads are also useful to seals and whales that can use them to breathe and for birds that can feed on marine prey through the lead.

lichen - Symbiotic association of alga and fungus. The fungus provides protection and moisture, the photosynthetic algae provide food for the fungus. Lichens are the toughest form of plant life and can live in some of the coldest and most exposed places in Antarctica as long as they have a rock to cling to. They can actively grow and photosynthesize at well below freezing point - albeit very slowly.

limnology - The study of freshwater such as lakes, ponds, and marshes. The analysis of the physical and chemical characteristics of the freshwater as well as the plants and animals that live within them. Antarctic lakes are more affected by climatic and other changes than is the ocean and so they are seen as giving an early warning of any impending changes.

longitude - Imaginary lines that wrap around the Earth intersecting at the north and south geographic poles. Lines of longitude are numbered from 0° (the Greenwich Meridian, passing through Greenwich in London, England) to 180°. Longitudes are called east if they fall east of the Greenwich Meridian, and west if they fall west of the Greenwich Meridian. Lines of longitude are all of the same length.


magnetic storm
- Times when the sun radiates large amounts of ions and electromagnetic energy out towards the solar system, tied to sunspot activity. This influx of high energy disturbs the Earth's magnetic field causing interruptions to telecommunications broadcasts and particularly pretty auroras.

marine biology - The study of plants and animals living in the seas and oceans.

maritime - Bordering or next to the ocean or sea. Maritime climates are oceanic climates, and are milder than the inland climates because of the moderating influence of the sea which acts as a huge heat sink absorbing heat in the summer and giving it out in the winter.

meteorology - The study of the Earth's atmosphere and the movements of air and moisture within the atmosphere. Includes the study of the atmosphere for weather forecasting.

meteorite - Fragments of rock that reach the Earth from beyond the atmosphere. Most are believed to come from asteroids, some are believed to be pieces from other planets. Antarctica is a particularly good place to find meteorites as they show up against the snow and ice and are accumulated in some places by the flow patterns of ice streams and glaciers.

migrate - Moving from one area to another. Some animals migrate in certain seasons to find better conditions, such as weather, food, or for breeding. Many whales migrate to the Southern Ocean in the summer to feed on the large the quantities of krill for example.

moss - Small, leafy-stemmed plants that grow in carpet-like mats and tufts on moist ground. Particularly abundant in maritime regions of Antarctica where conditions are too harsh for other types of plant. In Antarctica mosses often accumulate in large "moss banks".


nekton - Free-swimming aquatic animals that move under their own power and can move independently of ocean currents. Whales, squid and many fish are types of nekton.

niche - The life style of an organism, its "job" also - the place in which it lives, what it eats, how it gets nutrients, and the interplay it has with the environment and other organisms.

nip / nipped - a dreaded description of a ship from the early days of polar exploration when she was trapped by ice on both sides that was pushing in hard. In contrast to the gentle sounding nature of the event, the reality was often that the ship suffered considerable damage or was broken and sunk.

nunatak - An isolated peak of bedrock that sticks above the surface of an ice sheet. They are the peaks of hills and mountains standing above the ice sheet which flows around them. They offer important information about ice covered regions as they provide a sample of the rocks that lie under the ice.


oceanography - The study of the ocean. The physical properties of the ocean - currents and waves (physical oceanography), the chemistry of the ocean (chemical oceanography), the geology of the seafloor (marine geology), and the organisms that live in the oceans (marine biology and marine ecology).

ordinary katabatic wind - Short-lived katabatic winds with constant direction but a highly variable speed. Originate in cold dense air flowing coastward from the high Antarctic plateau over the pole.

ozone layer - A layer in the Earth's upper atmosphere, the stratosphere that contains almost 90% of the Earth's ozone. This forms a protective blanket against the harmful ultra-violet rays coming form the sun.


pack ice - Often used interchangeably with sea ice. Pack ice is frozen sea that formed somewhere else and has floated to its present position carried by wind, tides and currents. It is broken up and of variable size and thickness, some pieces can be the size of a coffee table and about 1 foot (30cm) thick, other pieces are larger than a tennis court and can be 30ft (9m) or more thick. Usually pack ice is in its second season.  Sea-water

    Open pack - when the pieces of ice don't touch
   Closed pack - when the pieces of ice touch

pancake ice -  Pancake ice grows from thickened grease ice and resembles pancakes or lily pads. The edges of each piece is upturned because the plates bump into each other as they gently move around in the sea. Usually between about about a foot (30cm) and 6 feet (2m) across. Pancakes tend to be smaller the closer to the shore line they are. Sea-water

physical oceanography - The study of the physical aspects of the seas and oceans such as the temperature, salinity, density variation, and the optic and acoustic properties of the ocean. Also includes the study of nature of currents, waves, and tides.

phytoplankton - Plant plankton. Microscopic free-swimming or suspended marine or freshwater plants within the plankton. Plankton is defined as being those organisms that inhabit the upper regions of a body of water, but cannot move about against the influence of water movements such as currents, they move generally with the water although may be able to move small distances. Phytoplankton includes diatoms and other photosynthetic algae, a crucial part of almost all aquatic food webs.

plate tectonics - A theory that ties together many observations made about the activity and movement of Earth's crust (earthquakes, volcanoes) and creation of ocean basins. Plate tectonics divides the surface of the globe into a number of rigid plates that move around the earth's surface over the period of millions of years.

polar - To do with the regions of the north and or south poles of the planet. The poles are cold, icy regions, a polar climate is a cold climate, with average temperatures less than 10°C (50°F).

polar easterlies - Winds that blow from the east as they flow off the high Antarctic polar plateau. Polar easterlies help generate ocean surface currents (east wind drift) in the Southern Ocean.

Polar Front (Antarctic Convergence) - A surface boundary where which the colder, north flowing Antarctic Surface Waters sink beneath warmer circulating waters. This marks a change in the oceans surface temperature and also chemical composition. North of the convergence, the area is known as the sub-Antarctic.

Polar Plateau - The relatively flat, high altitude central region of the East Antarctic Ice Sheet. The plateau has an average height of 2000 meters (about one mile) above sea level and a smooth surface with a small slope towards the coast in all directions.

polynyas - A polynya is an area of open water in pack ice or sea ice, they may be kept open by constant winds or the upwelling of water and so tend to recur in the same locations year after year. They are particularly important for wildlife as they allow mammals such as whales and seals to have a breathing hole and birds access to the sea in order to fish.

precipitation - Rain, snow, hail, sleet etc. moisture falling from clouds to the surface of the Earth, usually as rain, snow, and ice. The amount of precipitation is always measured as water or rain equivalent so allowing for the fact that snow can have various structures and densities

productivity - A term used to describe the rate of production in an ecosystem. Extra nutrients usually increase productivity.


reflectivity - The amount of light or energy that bounces off a surface relative to the amount of light or energy that reached the surface. A mirror is an example of an object with high reflectivity. The ocean has low reflectivity. Reflectivity may also be called albedo.

rookery - A colony of rooks, the term is also used for a colony of penguins.

rotten ice - Old ice, partially melted and often honeycombed


Sastrugi - wind blown snow
picture courtesy NOAA

salinity - The amount of dissolved salts contained in sea water. The average salinity of sea water is 35 parts per thousand, but can vary with location.

sallying a ship - from the early days of polar exploration, causing the ship to roll by crew and passengers running from side to side to prevent adhesion of the ice around her.

sastrugi - Irregular ridges of snow on a small scale (rarely more than 1 foot, 30cm) that lie parallel to the direction of the wind. Sastrugi can make travel very awkward or difficult, they can be quite soft or as hard as ice.

sea ice - A general term for any ice that forms from frozen seawater. Sea ice covers large parts of polar waters in the winter and melts back each summer.

sleet - Frozen or partially frozen rain that form when rain passes through a layer of air that is below the freezing temperature, falls to earth as a slush. Freshwater.

snow blindness - A painful condition caused by the reflection of uv light from snow and ice causing sunburn of the front layers of the eye, the conjunctiva and cornea. This can happen even in overcast conditions if some kind of lens is not worn to reduce the brightness of the light. The treatment is to avoid exposure to bright light until the eye has healed naturally.

South geographic pole - 90°S. The south geographic pole is the southern location where the axis of rotation of Earth intersects Earth's surface.

South geomagnetic pole - The point on Earth's surface in the Southern Hemisphere where the axis of the Earth's magnetic pole intersects. The south geomagnetic pole is approximately 1160 kilometres (725 miles) north of the south geographic pole (think about it). The south geomagnetic pole is tilted about 12 degrees to the axis of rotation of the Earth (geographic pole).

South magnetic pole - the point on Earth's surface that a south-seeking compass needle seeks. At the South magnetic pole a compass needle will point vertically downwards. This point is currently off the coast of Wilkes Land and wanders around.

stratosphere - The layer of the atmosphere that is above the troposphere, it extends from approximately 10 to 50 kilometres (6 to 31 miles) above Earth's surface. The upper region contains the ozone layer.

subglacial - Underneath the glacier.

supercooled - A condition when water is still liquid even though it is at a temperature at which it normally would freeze. Often under these conditions a small physical movement a small knock or tap will cause the water to freeze almost immediately.


tabular iceberg - A flat-topped iceberg, like a table. Freshwater.

terrestrial - Dry land. Terrestrial flora and fauna live on land not in water.

tide crack - Any crack in sea ice that is caused by the rise and fall of the tide. As the tide rises so the area of the sea increases and a crack forms, as the tide falls, so the area decreases and the crack closes. Often form around offshore rocks, between the shore and sea-ice, around grounded ice bergs or even stretching for miles between islands.

tongue - A mass of ice projecting from a glacier into the sea. It is still fixed to and forms a part of the larger glacier. freshwater

trade winds - One of three major circulation cells in both the northern and southern hemispheres. The trade winds from approximately 0° to 30° north or south latitude. Within the regions of the trade winds, prevailing winds blow toward the west. They were given their name as in the days of sailing ships, they aided the progress of the ships and hence the trade of goods carried by those ships.


ultraviolet radiation (UV) - A part of the electromagnetic spectrum that has shorter wavelengths than visible light. Ultraviolet radiation has more energy than visible light and can damage tissue (like human skin). Much of the ultraviolet radiation from the sun is absorbed within the ozone layer before it reaches the Earth's surface.

upper atmosphere physics - The study of processes that take place in the upper atmosphere. Includes study of the interactions between the various atmospheric gases and cosmic radiation, such as the ozone layer.

upwelling - An oceanographic term, the rising of deeper waters to replace surface waters. Upwelling often brings waters rich in nutrients to the surface, resulting in a region where ocean productivity is high.


West Wind Drift (Antarctic Circumpolar Current) - A Southern Ocean surface current flowing east and driven by westerly winds. The West Wind Drift carries a large volume of water and it is a strong current because no continents are in the way of the flow path.

white-out - A weather condition in which the horizon cannot be identified and there are no shadows. The clouds in the sky and the white snow on the ground blend - described as like walking along inside a ping-pong ball. White out conditions are potentially dangerous because it is difficult to find a point of reference and it is very easy to walk over a cliff or fall down a crevasse in such conditions.

wind chill - A way of describing the temperature that takes into consideration the effect of the wind speed in the temperature reported. Wind makes any temperature feel colder and wind chill factor is a way of expressing how cold the wind might make the temperature feel. First described after experiments by the American scientist Paul Siple on baked bean cans containing water and a thermometer left in the wind.


zooplankton - Animal plankton. Microscopic free-swimming or suspended marine or freshwater animals within the plankton. Plankton is defined as being those organisms that inhabit the upper regions of a body of water, but cannot move about against the influence of water movements such as currents, they move generally with the water column although may be able to move small distances. Many marine animals spend part of their lives as zooplankton, often as a juvenile life stage. One of the most important components of the Antarctic zooplankton is krill.

Antarctic glossary A - H  |  Antarctic slang