A level section</p><p>glossary

Glossary

Ablation zone

the area of a glacier or ice sheet with a negative net balance (where ablation exceeds accumulation). In Antarctica most ablation (loss of ice mass) occurs through iceberg calving where glaciers meet the sea. The air temperature is usually too cold for melting to occur.

Accumulation zone

the area of a glacier or ice sheet with a positive net balance (where accumulation exceeds ablation).

Adapted

a physical or behaviour trait that helps a plant or animal survive in its habitat.

Adiabatic

refers to the temperature change of an 'air parcel' associated with its rising or descending through the atmosphere (air expands as it rises and air is compressed as it descends).

Adventure travel

tourism involving exploration or travel to remote, exotic or possibly hostile areas where travellers should expect the unexpected.

Aeronomists

a person who studies the upper atmosphere, especially of regions of ionized gas.

Albedo

the amount of reflectivity of a surface, usually expressed as a percentage. Fresh snow has a high albedo, reflecting around 85% of the solar radiation hitting it.

Algae

Photosynthetic single-celled or multi-cellular organisms that are eukaryotes (cells with a nucleus as opposed to bacteria) but more simple in structure than plants. The largest forms of algae include various types of seaweed (such as kelp), and single-celled forms include diatoms, dinoflagellates, and coccolithophores (which together comprise most marine phytoplankton). Algae are a very diverse group found in a wide range of terrestrial and marine environments, and some types live in symbiotic relationship with other organisms (such as with fungi in lichens or with corals in coral reefs).

Angle of incidence

in studies of climate this factor refers to the angle at which sunlight hits the Earth's surface. If the Sun is directly overhead, then the angle of incidence is 90°. The angle of incidence at any one place changes with the seasons; but away from the tropics, the angle is always less than 90°, and declines as latitude increases. In general, low angle sunlight imparts less energy per unit area to the surface because it is more spread out and because at an oblique angle, sunlight has to pass through more atmosphere before it reaches the surface.

Antarctic Circle

the latitude corresponding to 66.56°S (or 66°33'39''S). Due to the tilt of the Earth's axis of rotation at 23.44° relative to the plane of the orbit, the sun does not rise above the horizon anywhere south of the Antarctic Circle during the winter solstice of the Southern Hemisphere (21st June).

Antarctic Circumpolar Current

an ocean current that flows from east to west around Antarctica. It is the largest ocean current connecting the Atlantic, Pacific and Indian ocean basins. It keeps the warm ocean waters away from Antarctica, enabling Antarctica to maintain its huge ice sheets.

Antarctic Treaty System

regulates international relations in respect to Antarctica. Signed by 46 countries, Antarctica is preserved as a continent for peace and science under the treaty.

Arête

a steep 'knife-edged' ridge of rock due to glacial erosion on either side of an area of high ground.

Aridity

Dry environment that lacks moisture, insufficient rainfall to support trees or woody plants.

Arthropod

a member of Phylum Arthropoda of the Animal Kingdom. Arthropods are invertebrates characterised by an external skeleton and segmented body with jointed limbs. They include insects, spiders, and crustaceans (such as crabs, lobsters, and shrimp).

Astrophysicists

scientists who study the physics of the universe including the physical properties of galaxies, stars and planets.

Austral

referring to the Southern Hemisphere.

Austral summer months

November to March

Autotroph

in ecology this refers to an organism that produces its own food. Autotrophs are the 'producers' in an ecosystem that underpin the food chain, and they are mainly plants and algae (and some types of bacteria) that photosynthesise. However, there are also types of bacteria that can manufacture their own food from non-photosynthetic chemical reactions (chemoautotrophs), notably at hydrothermal vents in the deep sea where sunlight is absent.

Benthic

organisms that live on the sea bed (or at the bottom of a lake).

Biodiversity

usually used to refer to the number of different types of organisms (quantity of different species) found in an area or ecosystem.

Biologists

scientists who study organisms and their relationship with their environment

Bioprospecting

the search for previously unknown chemical compounds or genes from flora and fauna in the interests of producing useful products such as medicines.

Biosphere

refers to the zone of life on the Earth. The biosphere overlaps and interacts with the lithosphere, atmosphere, and hydrosphere.

Biota

the combined flora and fauna of a region

British Antarctic Survey

is part of the Natural Environment Research Council (NERC). For 60 years has undertaken Britain's scientific research on and around Antarctica.

By-catch

unwanted and untargeted species which are caught while fishing. E.g. Turtles, whales, seals and birds.

Calve

when pieces of tidewater glacier break off and fall into the sea.

carbon footprint

the measure of the impact our activities have on the environment, in particular on climate change. It relates to the amount of greenhouse gases produced in our day to day lives through burning fossil fuels for electricity, heating and transportation.

Cirque glacier

a glacier contained within a shady, sheltered depression on the side of a mountain. Over time glacier erosion excavates the depression into an amphitheatre-shaped hollow called a cirque (or corrie).

Claims

a legal declaration of control over areas of land in Antarctica. 7 nations made 8 territorial claims to land in Antarctica below the 60°S before 1961.

Climatologists

a scientist who studies long term trends in the climate.

Cold-based

refers to glaciers (or parts of glaciers) where the glacier ice at the base is frozen onto the underlying bedrock (average temperature of basal ice well below 0°C). Where glaciers are cold-based, the speed of glacier flow is much slower than where glaciers are warm-based.

Cold War

rivalry after World War II between the communist Soviet Union and its satellites and the democratic United States and other countries of the western world.

Colonisation

where any one or more species populates a new area

Consumers

organisms that cannot produce their own food as autotrophs can. They must consume other organisms to gain energy.

Continental crust

the part of the Earth's crust that makes up the continents (and their continental shelves). Continental crust is on average less dense than oceanic crust, as well as being thicker and usually much older.

Continental shield

in geology this refers to tectonically stable areas of ancient continental crust that usually form the core of major continental regions. The exposed bedrock is mainly hard igneous and metamorphic rock, and the topography tends to be relatively flat.

Coriolis Force

an 'apparent' force caused by the rotation of the Earth which causes air that is already in motion to be deflected from the direct course between high and low pressure. The deflection is to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. Atmospheric pressure together with the Coriolis Force determine the global-scale prevailing winds found at different latitudes (e.g. Trade winds, Westerlies, Polar easterlies).

Crevasses

fractures and cracks extending down through glacier ice caused by internal stresses related to variations in the velocity of ice flow within and across a glacier.

Cryosphere

refers broadly to the world's ice and the places where the physical processes associated with ice play a major role (e.g. places under the influence of glaciers, ice sheets, sea ice, or permafrost).

Decomposers

in ecosystems the decomposers (primarily bacteria and fungi) fulfil the important function of breaking down organic matter to release nutrients to the soil which can later be taken up by plants. They play a key role in 'nutrient cycling'.

Depleting populations

decline in fish numbers

Dew point temperature

this is the temperature to which a 'parcel of air' must be cooled to reach saturation (relative humidity of 100%). Provided that there are surfaces on which vapour can condense, the process of condensation begins when the dew point temperature is reached - high in the atmosphere this leads to the formation of clouds; whereas at ground level it leads to fog, dew, or frost. The actual temperature varies depending on how much water vapour a parcel of air contains before it is cooled. (E.g. the dew point temperature of moist air will be higher than that of drier air.)

Disposable income

the part of a person's income remaining after deducting income tax.

Dykes

sheet-like intrusions of igneous rock that tend to run approximately vertically through surrounding rock (cutting across pre-existing bedding planes). Found in areas that were affected by volcanic activity.

Ecosystem

a concept referring to the links and interactions of organisms with each other and with their physical environment. Ecosystems can be studied at a range of scales from the functioning relationships existing on a rock or in a lake up to the scale of the whole planet. Key attributes of different ecosystems include levels of productivity, rates of nutrient cycling, and numbers of different species.

Ecological balance

equilibrium and harmonious co-existence of organisms and their environment.

Ecosystem

a system formed by the interaction between a community of organisms with their environment.

Eco-tourism

travel to fragile, pristine and usually protected areas that strives to be low impact and (often) small scale. It helps educate the traveller; provides funds for conservation; directly benefits the economic development and political empowerment of local communities.

Eco-friendly

same as environmentally friendly. Goods and services considered to inflict minimal or no harm on the environment.

Endangered

population of an organism which is at risk from becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters.

Endemic

a term used to indicate that a species is local (and native) to a particular area and has a restricted distribution. Often, endemic species become threatened when 'alien' species (species from elsewhere) are introduced into their environment by people.

Energy balance

in studies of the Earth's climate the term energy balance is used to refer to the balance between energy input from the Sun and energy output to space from terrestrial long wave radiation. Over long periods of time, the energy inputs and outputs to the Earth as a whole are in balance – otherwise the Earth would heat up or cool down to extremes. However, climate factors (such as an increase in atmospheric greenhouse gases) can alter the energy balance over the short-term causing the atmospheric temperature to adjust (either by heating up or cooling down to reach a new balance). The energy balance varies across the Earth with low latitudes having a surplus of energy and the poles a deficit. The energy balance across the surface of the Earth is equalised through the transfer of heat polewards (e.g. by ocean currents, winds, and weather systems).

Eustatic

refers to global change in sea-level related to the volume of the oceans, as opposed to local sea-level change brought about by uplift or subsidence of land. Over the past two million years or so, large eustatic sea-level changes have occurred due to changes in the amount of the planet's water locked up in ice sheets and glaciers. (When ice sheets melt, water is returned to the ocean and sea-level rises.)

Environmental impact

affecting the environment in a negative way.

Environmentalists

persons involved in the social movement centred on a concern for the conservation and improvement of the environment.

Eutrophication

a process whereby an ecosystem becomes loaded with nutrients (eutrophic) and the productivity of some autotrophs is increased. In water bodies this can have the negative effect of stimulating algal blooms to the detriment of other aquatic organisms. (The bloom reduces the penetration of light through the water column and causes depletion of dissolved oxygen as the algae decays.)

Extinction

the death of every member of a species or group of taxa (group of organisms).

Feedback processes

processes in which an initial change to the system triggers subsequent changes which either amplify (positive feedback) or dampen (negative feedback) the effects of the original change.

Flood basalts

extensive areas of basalt rock (either on land or on the sea floor) formed from the release of enormous quantities of basaltic lava from very large scale eruptions in the past.

Flora and fauna

plant and animal life.

Food web

a food web is made up of individual food chains which describe the eating relationships between species within an ecosystem

Fungi

include a huge diversity of organisms ranging in size from micro-organisms (such as yeast) to larger forms (such as mushrooms). They are eukaryotic organisms (cells contain a nucleus); but are in their own taxonomic kingdom distinct from plants and animals. Along with bacteria, fungi play the essential role of decomposing organic matter in ecosystems to free up nutrients for continued autotroph productivity.

Geologists

a scientist who studies the physical structure and processes of the earth.

Geomorphological work

refers to the 'work' done in shaping a landscape by geomorphological agents, such as the action of water, wind, and ice.

Gillnet fishing

a fishing method used by commercial fisheries where the net size, twine strength and net length and width is designed specifically for the target species in order to reduce by-catch. The fish can swim forward into the net but are unable to swim back out without their gills becoming caught.

GIS

Geographical Information Systems is usually taken to refer to a type of information technology that is concerned with the storage, manipulation, analysis, and querying of spatially-referenced data. There are many kinds of GIS programmes, but most allow the user to manipulate a base map by selecting different types of information for display on the map, depending on the subject of study. For an accessible introduction to GIS, follow this link: Ordnance Survey GIS Zone

Glacial abrasion

the erosional process in which rock material frozen to the base of a glacier abrades underlying rock as the glacier moves.

Glacial/interglacial cycles

Large-scale fluctuations in the area of land covered by glacier ice associated with large sea-level change, temperature change, and changes in the distribution of plants and animals. These cycles have been occurring since the start of the Quaternary Period (2.6 million years ago) and over the past million years the cycles have occurred on a 100,000 year frequency. During the height of the last glacial, the area covered by ice sheets was roughly three times what it is today, with most of the increase in the Northern Hemisphere.

Glacial plucking

the erosional process in which glaciers loosen, detach, and pick up chunks of rock from their beds.

Glacials

phases when ice sheets covered a much greater area than today (particularly in the Northern Hemisphere) and sea-levels were over 100 metres lower. The global climate is also colder and drier during glacials. The last glacial reached its maximum approximately 20,000 years ago.

Glacier

a mass of ice resting on land that deforms under its own weight and flows downslope. Glaciers exist at a range of scales from small cirque glaciers to large ice sheets.

Glacier ice

the ice making up glaciers. It is distinguished from other types of ice by being formed through the compaction of pre-existing snow and frost crystals as, over time, they become buried under successive layers of more recent snowfall.

Glaciologists

scientists who study glaciers, or more generally ice and natural phenomena that involve ice. Glaciologists are interested in glacial history and the reconstruction of past glaciation.

Globalisation

a term used for a wide variety ways in which countries and peoples across the world are becoming increasingly interconnected. Globalisation involves, for example, global integration of economic activity, technology, politics, and culture.

Glycoproteins

group of conjugated proteins that contain a carbohydrate as the non-protein component. Glycoproteins play essential roles in the body. In the immune system almost all the key molecules involved in the immune response are glycoproteins.

Harvest fish

to catch, take or remove fish from the ocean.

Holocene

the geological epoch in which we live, being the second epoch of the Quaternary Period. It is an interglacial and it started 11,700 years ago.

Hydrothermal vents

places where water, heated by geothermal energy from the Earth's interior, comes out of the Earth's crust. On land, hydrothermal vents include hot springs and geysers; whereas under the ocean they can form features known as 'black smokers'. Oceanic hydrothermal vents are particularly fascinating from an ecological point of view as they support benthic ecosystems in which the food chain is underpinned by chemosynthesis rather than photosynthesis. Autotrophs of black smokers synthesise organic matter through the oxidation of hydrogen sulphide.

Iceberg

a large piece of freshwater ice that has broken off from a snow formed glacier or ice shelf and is floating in open water.

Ice floes

frozen masses of seawater that float on the surface of the sea. Usually relatively flat piece of sea ice that is free moving

Ice rafted debris

glacially eroded debris carried in icebergs or ice floes that drops down to the sea floor when the iceberg melts. Layers of coarsely-textured ice rafted debris found in marine sediments indicate how far icebergs travelled across the sea (and the quantities of icebergs) at various times in the past.

Ice sheet

a continental sized glacier, at least 50,000km2 in area. Ice sheets are dome-shaped with flow of ice outward from the centre. The East Antarctic Ice Sheet is the largest ice sheet in the world.

Ice shelves

where glaciers or ice sheets advance to the coast and continue into the sea, ice shelves are their floating extensions. Towards the coast, the ice shelf ends at the 'grounding line' where the glacier ice is in contact with its bed. Beyond the grounding line the ice is floating, and at the seaward end of the ice shelf, glacier ice is discharged to the sea through the process of calving (the breaking off of chunks of ice, forming icebergs). Ice shelves can be many hundreds of metres thick.

Ice stream

a relatively narrow zone of glacier ice issuing from an ice sheet that has a flow velocity much greater than the surrounding ice. The velocity of an ice stream can exceed 1000m per year because of the presence of meltwater at its base (causing it to be warm-based, rather than cold-based and frozen to its bed). Ice streams are responsible for much of the discharge of ice from the Antarctic and Greenland Ice Sheets.

Igneous intrusions

masses of igneous rock formed inside pre-existing crustal rocks from the injection, cooling, and crystallisation of magma.

Incidental bird deaths

unintentional deaths of birds due to fishing.

Interglacials

phases of relative warmth between glacial times when ice sheets are much less extensive and restricted to the polar regions. We currently occupy the Holocene Interglacial.

Intergovernmental Panel on Climate Change (IPCC)

Established in 1988 by the World Meteorological Organisation and the United Nations Environment Programme, the IPCC has the function of bringing together experts from across the world to assess the latest research on climate change and to provide policymakers and world leaders with an authoritative source of information. The most recent IPCC report was the Fourth Assessment (AR4) published in 2007. The IPCC reports contain three sections (Working Groups I, II, III) covering the science of climate change, the potential impacts and means of adapting, and various strategies for reducing emissions and mitigating climate change. The Fourth Assessment had more than 800 contributing authors with over 2500 people involved in its peer review.

Isostasy

the phenomenon of buoyancy of the Earth's crust on the more mobile mantle in which a change in the load in a particular place will cause localised subsidence or uplift of the land. This can lead to local, or regional-scale changes in sea-level caused by the land moving up or down relative to the sea (isostatic sea-level change in contrast with eustatic sea-level change). For example, areas of Scotland are still rising (a millimetre or so per year) in response to the melting away of the British Ice Sheet following the last glacial (the removal of this weight has made the crust more buoyant causing isostatic adjustment).

Katabatic

refers to downslope winds which can be of cold or warm types. Cold katabatic winds occur in places where surface air becomes chilled, and therefore relatively dense. It then flows downhill (cold air drainage) and can reach high velocities where the air is funnelled into valleys and/or where gradients are steep.

Kayaking

moving across the water in a small boat similar to a canoe but with a different sitting position and paddle.

krill

shrimp-like marine invertebrate. Important in the food web as baleen whales, manta rays, white sharks, crabeater seals and other seals and a few other sea birds feed almost exclusively on them. In the Southern Ocean, Antarctic krill makes up an estimated biomass of over 500 million tons, roughly twice that of humans. Of this over half is eaten by whales, seals, penguins, squid and fish each year. Commercial krill fishing is conducted in the Southern Ocean most of which is used for aquaculture, aquarium feeds, bait in sport fishing or in the pharmaceutical industry.

Latent heat

the energy that is either absorbed or released as a substance changes state. For example, latent heat is released to the surrounding atmosphere when water vapour condenses into liquid droplets (or ice crystals) forming clouds.

Long line fishing

a type of commercial fishing which uses a long line with baited hooks attached at intervals by means of branch lines called snoods. A snood is a short length of line which is attached to the main line using a clip or swivel, with the hook at the other end. Lines can also be set by means of an anchor, or left drifting. Hundreds or even thousands of baited hooks can hang from a single line. Swordfish, tuna, halibut, sable fish and many other species are commonly targeted by long liners.

Long lines can be set to hang near the surface to catch fish such as tuna and swordfish or along the sea floor for ground fish such as halibut or cod. Long line fishing is prone to incidental catching and killing of sea birds and sea turtles. Compared to other fishing methods such as bottom trawling, long line fishing results in relatively little destructive impact on the bottom of the seabed habitats.

Low pressure system

low pressure systems are areas where there is relatively low atmospheric pressure at the surface. This causes air from elsewhere to move into the low pressure area and rise. Air circulates around the low pressure centre (rotating anticlockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere) due the Earth's rotation, thereby causing weather fronts as cold air is pulled to lower latitudes and warmer air to higher latitudes. Low pressure systems (also termed 'depressions') tend to form in the mid-latitudes near the polar front, and they are important for creating precipitation and transferring energy from lower to higher latitudes.

Madrid Protocol 1991

The parties of the Antarctic Treaty adopted a protocol to provide comprehensive protection of Antarctica. The Protocol designates Antarctica as a nature reserve dedicated to peace and science. The Protocol has 14 annexes outlining the protection of Antarctica including the banning of mining and special environmental principles for the conduct of all activities on Antarctica.

Manual workers

workers involved in jobs involving physical work done with the hands. E.g. building, road building, fruit picking.

Mass balance

in relation to glaciers, the mass balance refers to the balance between accumulation (through snowfall) and ablation (through melting, or in the case of Antarctica, largely through iceberg calving off the edge of ice shelves). If its mass balance is positive, a glacier grows and its terminus advances. If negative, the glacier loses mass and its terminus retreats.

Meltwater

water released by the melting of snow or ice, including glacial ice and ice shelves over oceans. Meltwater is often found in the ablation zone of glaciers, where the rate of snow cover is reducing.

Metric tonnes

a measurement of mass equal to 1,000 kilograms.

Meteorites

solid objects from space that have survived travel through the Earth's atmosphere without being completely burnt up to reach the surface. The main types of meteorites are either stony, metallic (usually iron-nickel), or a combination of the two.

Milankovitch cycles

named after the Serbian scientist Milutin Milankovitch who first calculated them, the Milankovitch cycles refer to three long-term variations in Earth's orbit – eccentricity, obliquity, and precession – that change the seasonal distribution of solar energy reaching the Earth. These subtle, yet important, changes have been described as the 'pace-maker' of the glacial/interglacial cycles. Approximately, eccentricity refers to a 100,000 year cycle in how elliptical the Earth's orbit is, obliquity refers to a 41,000 year cycle in how tilted the Earth is on its axis, and precession refers to a 23,000 year cycle in the distance between the Earth and the Sun during different seasons (e.g. today our Northern Hemisphere summer occurs near the point where the Earth is furthest from the Sun on its orbit, but this was reversed about 11,000 years ago).

Mineral exploitation

taking minerals such as oil, coal, gold and iron out of the earth or sea for use for energy or in the production of products.

Moraine

an accumulation of glacial debris, either on or around an active glacier or left behind as a glacial deposit. Collectively, the glacial debris is called till and is typically 'unsorted' and 'unstratified' (i.e. it contains a range of particle sizes and is not clearly layered like deposits from lakes and rivers).

Non-native species

species that are not native to an area are introduced from other ecosystems. Non-native species can upset the existing balance and can cause harm or devastation to the established plants and animals of the ecosystem. When alien species enter into an ecosystem, they can disrupt the natural balance, reduce biodiversity, degrade habitats, transmit new diseases to native species and further jeopardise endangered plants and animals.

Nunataks

isolated areas of rock that protrude above the surface of an ice sheet.

Oceanic crust

The part of the Earth's crust that underlies the oceans. It has a greater average density than continental crust, and is thinner and usually much younger.

Pelagic

refers to marine organisms that live in the upper layers of the ocean.

Phytoplankton

the producers (autotrophs) within the plankton that gain their energy through photosynthesis (plankton referring collectively to organisms that float and drift with the currents). Phytoplankton include a range of different micro-organisms, the most abundant types being dinoflagellates, diatoms, and coccolithophores.

Polar desert

refers to high latitude areas in both hemispheres characterised by low precipitation (less than 250mm per year) and a cold climate, with temperatures below freezing much of the time. The landscape may or may not be covered with ice, for example parts of Antarctica's polar desert are ice free, such as the McMurdo Dry Valleys.

Polar cell

in the general circulation of the atmosphere, the polar cells refer to large-scale circulations of air in each hemisphere in which cold air descends onto the poles and moves over the surface to lower latitudes. At about 60° latitude, along the polar front, polar air meets milder mid-latitude air, and air rises to create low pressure systems.

Polar easterlies

the prevailing winds at high latitudes which are related to the polar cells. As air moves across the surface, away from polar high pressure and towards the lower latitudes, the Coriolis Force causes deflection (to the right in the Northern Hemisphere and to the left in the Southern Hemisphere) in the path taken by the air. Therefore, rather than take the most direct path to lower latitudes, this causes the wind to veer from the east towards the west.

Pristine

Antarctica is considered pristine because activities such as mining, development and military affairs are not permitted. Antarctica is protected and is devoted to science and peace. However, Antarctica does not remain completely untouched as there are more than 20 scientific bases in Antarctica and rubbish dumps from the past still remain, although these are in the process of being cleaned up

Pyramidal peak

a steep and sharp glacially eroded rocky peak caused by three or more cirque glaciers eroding back on different sides of a mountain. A famous example is the Matterhorn on the Swiss-Italian border.

Positive feedback

the type of feedback process in which an initial change to a system triggers a series of further changes that amplify the initial change. It is sometimes described as a 'snowballing effect'.

Quaternary Period

the most recent period of geological time, from approximately 2.6 million years ago up to the present day. It includes the Pleistocene and Holocene Epochs and is distinguished from earlier geological periods by being relatively cold on average, but also containing significant climate variation associated with the cyclic advance and retreat of large continental ice sheets (glacial/interglacial cycles). It is the most recent 'Ice Age' time in Earth's geological history.

Quotas

a method to try and regulate fishing because of the decimation of wild fish populations governments have set total allowable catches. Quotas are designed to allow fishing stocks to recover and fishing to become more sustainable.

Radiometric dating

a way of determining the age of various objects through measuring the amount of radioactive decay of radioactive elements contained within the object. There are several different radioactive elements that can be used for dating, each having a different decay rate (half-life) and hence different dating range. One of the most well known radiometric dating techniques is radiocarbon dating which enables the age of material containing radiocarbon (14C) to be determined back to an age limit of about 50,000 years.

Rational use

fishing in the Southern Ocean within the Conservation Area is permitted but at levels that ensure that stocks do not fall below an amount required for net increase.

Real terms

the value expressed in today's money.

Relative humidity

the amount of water vapour held in a body of air relative to the maximum that could be held given that body of air's temperature. When the relative humidity reaches 100%, air is said to be 'saturated' (having reached the dew point); and, provided there are surfaces available for vapour to condense onto, such as cloud condensation nuclei, the process of condensation will begin. If the amount of vapour in a body of air is held constant, then the relative humidity will increase as that body of air is cooled, because colder air cannot hold as much vapour as warmer air.

Remote sensing

refers to a range of techniques whereby observations and measurements are made remotely (e.g. from aircraft and satellites). Satellite imagery in particular is making an increasingly important contribution to many areas of physical geography and to monitoring environmental and climatic change.

Responsible travel

tourism that ensures that the heritage and environment of places tourists seek to visit does not disintegrate under the pressure of travel to those areas.

Retreat

a glacier with a sustained negative balance and therefore out of equilibrium will retreat. This results in a loss of ice.

Rifting

a tectonic process whereby crust is stretched and pulled apart. Over millions of years a rift zone can develop into a new divergent (constructive) plate margin. Rifting creates distinctive topography – where active rifting occurs on land, linear valleys are formed that are bordered by steep escarpments and contain active volcanoes. The East African Rift zone is one of the best known examples.

Salinity

the saltiness or dissolved salt content of a body of water or soil.

Sanctuaries

an animal sanctuary is a place where animals live and are protected.

Sea floor spreading

the tectonic process in which sections of oceanic crust move apart and new crust is formed in between. This process occurs at mid-ocean ridges and creates new sea floor. In other parts of the world, there is a compensating destruction of sea floor at subduction zones; and together, sea floor spreading and subduction are the mechanisms that change the configuration of the world's continents and oceans over geological time.

Sea ice

frozen sea water, usually two to three metres thick. Because of the salinity of the ocean, sea ice forms once the sea surface temperature drops to -1.8°C. Where sea ice is 'fastened' to the coastline, it is termed 'fast ice', and ice floes are formed when chunks of fast ice break away. Sea ice moved by wind and currents is termed 'drift ice'. In large masses, drift ice is called 'pack ice'. An area of open water within pack ice is called a 'polynya'.

Sills

sheet-like intrusions of igneous rock that tend to be roughly horizontal or tilted and aligned with the pre-existing bedding planes. Found in areas that were affected by volcanic activity.

Spatial data

refers to data with a locational aspect; for example, measures of the geographical distribution of natural or human features and phenomena.

Spores

a reproductive structure that is adapted for dispersal and for surviving in unfavourable conditions. Once conditions are favourable, a spore can develop into a new organism.

Stable isotope

isotopes are different forms of the same element in which an atomic nucleus has the same number of protons but a different number of neutrons; and if the isotope is stable, it does not undergo radioactive decay. Different numbers of neutrons alter the atomic weight of the element. For example, carbon-13 is heavier than carbon-12 because it has 7 neutrons rather than the usual six. These are both stable isotopes of carbon; however with eight neutrons, carbon-14 is a radioactive isotope.

Stratigraphical continuity

a characteristic of deposits that accumulate continuously through time so that when a cross-section of the deposit (or sediment core) is analysed, there are no breaks in the record of sedimentation (the stratigraphical record is said to be 'continuous'). Examples include sediments from peat bogs, lakes, and the sea floor, as well as ice sheets.

Stratosphere

the stratosphere is the second layer of the atmosphere, lying above the lowermost troposphere. Its lower boundary varies between about 7 and 20km altitude, and it extends up to about 50km. It is characterised by a temperature inversion due to the presence of ozone which absorbs ultra-violet radiation causing air to heat up. Temperature increases with height until the top of the stratosphere is reached (the 'stratopause').

Subduction

the tectonic process in which a section of oceanic crust descends into the mantle beneath another section of oceanic crust or a section of continental crust. The process of subduction is associated with plates moving towards each other (convergent plate boundaries), and the destruction of crust at subduction zones is compensated elsewhere in the world by the formation of new crust where there is sea floor spreading. Together, subduction and sea floor spreading are the mechanisms that change the configuration of the world's continents and oceans over geological time.

Sublimation

refers to the process in which an element or compound makes the transition between the solid and gas states without an intermediate liquid state. For example, ice can sublimate directly into water vapour in cold, dry climates.

Supercontinent

an agglomeration of two or more continents making up a much larger continental mass. Some 200 million years ago, all of the continents were joined into one supercontinent called 'Pangaea'. Pangaea split into two supercontinents

Laurasia in the north and Gondwana in the south, each eventually splitting into the individual continents that exist today. Over the course of Earth's geological history, it is thought that there have been as many as seven cycles of supercontinent formation and break-up.

Sustainable/sustainability

using the environment in a way that does not destroy it for future generations.

Sustainable tourism

where tourists use the environment in a way that maintains it and does not destroy it for future generations.

Sustainable yield

in ecology, this is the quantity of a living resource that can be harvested or exploited in some way by people without leading to long-term decline (or disappearance) in the resource. An example is the quantity of a species of fish that can be caught each year without jeopardising the ability of the population to reproduce itself. The concept can also be applied beyond species to other ecosystem resources such as forests, soils, rivers and lakes.

Temperature inversion

in the atmosphere this refers to air temperature increasing with height. In the lowest layer of the atmosphere (the troposphere) temperature normally decreases with increasing altitude because of the upwards reduction in air pressure. However, occasionally in certain places certain weather conditions lead to the formation of a temperature inversion in the lower atmosphere. A permanent temperature inversion exists just above the troposphere because of the presence of ozone in the stratosphere.

Temporal resolution

in stratigraphic studies (studies of layered deposits), this refers to how detailed the stratigraphic record is over a given time span. For example, ice cores have a high temporal resolution because it can be possible to identify annual layers and to reconstruct past changes on a year by year (and even seasonal) basis. In contrast, many sediment cores from the deep oceans have a low temporal resolution, making it impossible to identify changes on as precise a timescale as the ice cores. This is because marine sediments accumulate more slowly and because organisms living on the bottom of the ocean mix up the sediments as they are deposited – thereby blurring the record.

Tephra

solid material ejected from volcanic eruptions (pyroclastic material). It includes a range of sizes, encompassing volcanic ash, cinders, and 'bombs'.

Thematic information

scientific information that has a geographical location, such as rock type on a geological map.

Topography

the surface features of an area which can be represented on 'topographic' maps. It includes an area's relief, as well as any other natural or artificial features of the landscape.

Trawlers

a commercial fishing boat that is designed to drag fishing trawls. Trawls are large fishing nets that are dragged along the bottom of the sea or in midwater.

Trawler net cables

are cables that join the fishing nets to the boats. Fishing trawlers pull large nets through the water behind one or more trawlers (boats). Trawlers have been criticised for catching large numbers of unwanted species and therefore causing the unnecessary deaths of other fish and marine life.

Treaty

is a formal agreement between one more more states in reference to peace, trade and/or a document in which an agreement is set down.

Troposphere

the lowest layer of the atmosphere extending up to an altitude of around 20km at the equator and 7km near the poles. It contains most of the mass of the atmosphere, and is where the weather occurs. The top of the troposphere is termed the 'tropopause', and it is characterised by a permanent temperature inversion caused by ozone formed in the stratosphere (the atmospheric layer lying above the troposphere).

Truncated spurs

flattened spurs with steep faces caused by a glacier widening its valley. Prior to glaciation, the spurs may have been interlocking due to meandering and fluvial erosion by a former river; but through glacier erosion, the ends of the spurs are removed as the valley is widened and changed into the classic 'U-shaped' valley.

Valley glacier

a glacier that extends beyond a glacial cirque to fill part, or all, of a valley. Valley glaciers range greatly in size, with larger valley glaciers being fed by glaciers occupying smaller valleys known as 'tributary glaciers'.

Vascular plants

also known as 'higher plants', these plants have vascular tissues for transporting water, nutrients, and sugars through the plant. Vascular plants include flowering plants, conifers, cycads, ferns, horsetails, and clubmosses; and exclude, for example, mosses and liverworts.

Vulnerable species

a species which is likely to become endangered unless the circumstances threatening its survival and reproduction improve.

Warm-based

refers to glaciers (or parts of glaciers) where the glacier ice at the base is not frozen onto the underlying bedrock. Instead there is some water between the ice and its bed, enabling ice flow to reach much greater velocities than is the case where glaciers are cold-based.

Waste

rubbish or products no longer required. Human waste (urine and faeces).

Specific GIS terms

Point (node)

a feature that is represented by a single geographical position.

Line (arc)

a line feature that is made up by a series of points (nodes) joined together.

Polygon

a closed shape represented by a line that starts and finishes at exactly the same place. A polygon can be a regular shape such as a rectangular building or an irregular shape such as a lake.

Geometry

the points, lines and polygons in the data.

Attributes

information about the type and value of data associated with the geometry for example height is an attribute of a contour. Can be held either as text attached to the feature or in a table linked to it.

Topology

the relationships between the points, lines and polygons in the data, whether features are next to or connected to other features.

Vector

data that is made up of points, lines and polygons such as a map, where each feature has a geographical position..

Raster

data that is made up of a grid of cells with attributes that vary over the surface. For example a digital photo where each cell (pixel) has the attribute of colour, or a digital elevation model (DEM) where each cell has the attribute of a height value.