Glossary and Links | Glacier Monitoring in Switzerland GLAMOS

Glossary

For a general introduction on cryospheric elements (snow, glaciers, and permafrost), please refer to the thematic portal on the cryosphere of the Swiss Academy of Sciences (SCNAT). This thematic portal shows and explains selected long-term series of measurements on snow, glaciers, and permafrost. From the glacier monitoring the following parameters are explained and presented: length change, mass balance, and inventory.

The following glacier glossary is adapted from: M. Maisch & P. Wick: dns-Themenheft „Gletscher“, Nr. 7/8 (2004) and J. G. Cogley et al.: Glossary of glacier mass balance and related terms, IHP-VII Technical Documents in Hydrology No. 86, IACS Contribution No. 2, UNESCO-IHP, Paris (2011).

ablation

processes that lead to glacier mass loss, by melting and evaporation as a result of solar radiation, ice breaks or calving (into a lake or the sea).

ablation area

part of the glacier surface – usually the lower one – where the annual amount of ablation is greater than the amount of accumulation.

accumulation (on the glacier)

processes that provide mass to the glacier through precipitation (snowfall), wind drift, or avalanches.

accumulation area

part of the glacier surface - usually the higher one - on which the annual amount of accumulation is greater than the amount of ablation. In the accumulation area, snow first forms firn, which is later transformed into glacial ice.

accumulation area ratio

the ratio of the area of the accumulation area to the area of the entire glacier, abbreviated as AAR.

equilibrium line

(theoretical) line on the glacier where at the end of the hydrological year (end of summer season) accumulation and ablation balance each other. When the mass balance is balanced, the areas of accumulation and ablation are approximately in a 2:1 ratio. The elevation of the equilibrium line is abbreviated as ELA.

firn

snow that has survived at least one summer season and that has already transformed into the denser firn.

fluvio-glacial

processes and forms that come about through the combined action of ice and meltwater.

geodetic method

any method for determining mass balance by repeated mapping of glacier surface elevations to estimate the volume balance.

glacial

processes directly caused by the glacier and the resulting terrain or landscape forms.

glacier forefield

area between the moraines of modern (or post-glacial) advances (e.g. greatest extent as around 1850/60) and today's glacier outlines.

glacier snout

lower end of a glacier, where a stream of melt water usually emerges from the ice through the opening of a subglacial tunnel at the glacier front.

glaciology

science that deals with the (physical) properties and behaviour of snow, ice, glaciers, and permafrost.

greatest extent (e.g. as in 1850/60)

widespred glacier advances in the Alps, peaking around the middle of the 19th century, subsequent to previous advances of similar extent (e.g. as in 1600/40 and 1820). Marks the end of the "Little Ice Age" (in the Alps).

Holocene

post-glacial period, including the last 11,700 years since the end of the last glacial period.

hydrological year

period between the 1st of October and the 30th of September of the following year, i.e. fixed-date system with the first day of the mass-balance year always on the same calendar date.

Little Ice Age

generally cool phase of the climate and glacier history between the middle of the 13th and 19th centuries (in the Alps), characterized by generally large glacier expansion and several glacier advances in the order of the greatest extent as in 1850/60.

mass balance

difference between glacier accumulation and ablation over a specific time period. On several Alpine glaciers, the glaciological mass balance is measured on a regular basis. The mass balance unit kg m^-2 is usually replaced by the millimetre water equivalent, mm w.e. The units kg m^-2 and mm w.e. are numerically identical.

moraines

rock material that is accumulated by the glacier at the edge of the ice in the form of ridges (terminal and lateral moraines) or at the border between the ice and the ground (ground moraine). At the confluence of two glacial streams, the most prominent medial moraines emerge through the union of the lateral moraines.

observation period

floating-date system, where the mass-balance year is defined by the calendar dates of the two successive surveys, which may vary from year to year.

Quaternary

most recent period in the geologic time scale, with different cold periods and cyclic growth and decay of continental ice sheets (glacials/ice ages). Beginning about 2.6 million years ago.

rock glacier

tongue-shaped mass of debris, bead-like, moving downwards about 0.1–1.0 m per year, consisting of blocks of various sizes. Contains an (ice) core formed from permafrost in its active state.

seracs

due to the overlapping of longitudinal and transversal crevasses, mostly over steep slopes, a confused pattern of blocks or columns of glacial ice is formed, resulting in spectacular ice towers.

temperate glaciers

glaciers consisting of temperate ice around 0 °C, in contrast to cold glaciers with constantly lower temperatures.

terminal moraine

prominent ridge, often crossing the valley, horseshoe-shaped morainic deposit of a glacier which maintained its maximum extent for a prolonged period after an advance phase.

water equivalent (w.e.)

a unit, in full the "metre (or millimetre) of water equivalent", for describing glacier mass as the thickness of an equal mass having the density of water. 1 kg of liquid water has a vertical extent of 1 mm when distributed uniformly over a horizontal area of 1 m².

Swiss glaciers