Glaciology Explained

Glaciology (;) is the scientific study of glaciers, or, more generally, ice and natural phenomena that involve ice.

Glaciology is an interdisciplinary Earth science that integrates geophysics, geology, physical geography, geomorphology, climatology, meteorology, hydrology, biology, and ecology. The impact of glaciers on people includes the fields of human geography and anthropology. The discoveries of water ice on the Moon, Mars, Europa and Pluto add an extraterrestrial component to the field, which is referred to as "astroglaciology".^[1]

Overview

A glacier is an extended mass of ice formed from snow falling and accumulating over a long period of time; glaciers move very slowly, either descending from high mountains, as in valley glaciers, or moving outward from centers of accumulation, as in continental glaciers.

Areas of study within glaciology include glacial history and the reconstruction of past glaciation. A glaciologist is a person who studies glaciers. A glacial geologist studies glacial deposits and glacial erosive features on the landscape. Glaciology and glacial geology are key areas of polar research.

Types

Glaciers can be identified by their geometry and the relationship to the surrounding topography. There are two general categories of glaciation which glaciologists distinguish: alpine glaciation, accumulations or "rivers of ice" confined to valleys; and continental glaciation, unrestricted accumulations which once covered much of the northern continents.

Alpine – ice flows down the valleys of mountainous areas and forms a tongue of ice moving towards the plains below. Alpine glaciers tend to make topography more rugged by adding and improving the scale of existing features. Various features include large ravines called cirques and arêtes, which are ridges where the rims of two cirques meet.
Continental – an ice sheet found today, only in high latitudes (Greenland/Antarctica), thousands of square kilometers in area and thousands of meters thick. These tend to smooth out the landscapes.

Zones of glaciers

Accumulation zone – where the formation of ice is faster than its removal.
Ablation (or wastage) zone – when the sum of melting, calving, and evaporation (sublimation) is greater than the amount of snow added each year.

Glacier equilibrium line and ELA

The glacier equilibrium line is the line separating the glacial accumulation area above from the ablation area below. The equilibrium line altitude (ELA) and its change over the years is a key indicator of the health of a glacier. A long term monitoring of the ELA may be used as indication to climate change.

Movement

When a glacier is experiencing an accumulation input by precipitation (snow or refreezing rain) that exceeds the output by ablation, the glacier shows a positive glacier mass balance and will advance. Conversely, if the loss of volume (from evaporation, sublimation, melting, and calving) exceeds the accumulation, the glacier shows a negative glacier mass balance and the glacier will melt back. During times in which the volume input to the glacier by precipitation is equivalent to the ice volume lost from calving, evaporation, and melting, the glacier has a steady-state condition.

Some glaciers show periods where the glacier is advancing at an extreme rate, that is typically 100 times faster than what is considered normal, it is referred to as a surging glacier. Surge periods may occur at an interval of 10 to 15 years, e.g. on Svalbard. This is caused mainly due to a long lasting accumulation period on subpolar glaciers frozen to the ground in the accumulation area. When the stress due to the additional volume in the accumulation area increases, the pressure melting point of the ice at its base may be reached, the basal glacier ice will melt, and the glacier will surge on a film of meltwater.

Rate of movement

The movement of glaciers is usually slow. Its velocity varies from a few centimeters to a few meters per day. The rate of movement depends upon the factors listed below:

Temperature of the ice. A polar glacier shows cold ice with temperatures well below the freezing point from its surface to its base. It is frozen to its bed. A temperate glacier is at a melting point temperature throughout the year, from its surface to its base. This allows the glacier to slide on a thin layer of meltwater. Most glaciers in alpine regions are temperate glaciers.
Gradient of the slope.
Thickness of the glacier^[2]
Subglacial water dynamics

Glacial Terminology

Ablation : Wastage of the glacier through sublimation, ice melting and iceberg calving.

Glacial deposits

Source:

Stratified

Outwash sand/gravel :From front of glaciers, found on a plain.

Unstratified

Till-unsorted :(Glacial flour to boulders) deposited by receding/advancing glaciers, forming moraines, and drumlins.

External links

Notes and References

Williams . Richard S. . Summary Remarks . Annals of Glaciology . 1987 . 9 . 254–255 . 10.3189/S0260305500000987. 1987AnGla...9..254W . free.
Book: Mahapatra, G.B.. Text book of Physical Geology. 1994. 81-239-0110-0. Nazia printers, Delhi. 269.