Glaciers of Antarctica

Introduction | GLIMS glaciers | References | Comments |

Introduction

Antarctica has many different types of glacier.  They range from enormous ice streams, arteries of fast flow that discharge the majority of the ice from the centre of the ice sheet to its edges[1], to slow-moving cold-based glaciers that are largely frozen to their beds[2]. Most of the Antarctic continent’s coastline is composed of grounded or floating ice and ice shelves (93%)[3]. Of the glaciers that terminate in the ocean, they can be tidewater glaciers, ice-shelf tributary glaciers, or grounded outlet glaciers. Most of these drain the three large ice-sheets in Antarctica: the Antarctic Peninsula Ice Sheet, the West Antarctic Ice Sheet and the East Antarctic Ice Sheet. The West and East Antarctic ice sheets are divided by the Transantarctic Mountains.

In the video below, you can see a calving event at Jakobshavn, in western Greenland (video from Jason Amundsen, University of Colorado). The ice wall is 100 m high, with 900 m below water, and this is a full-thickness calving event of a grounded tidewater glacier.

GLIMS glaciers

The Global Land Ice Measurements from Space programme (GLIMS) defines many types of glaciers[4]. Many examples of these can be seen on James Ross Island or the Antarctic Peninsula (see map for location).

An Ice Sheet is a large expanse of ice, unconstrained by topography, and is continental size (e.g. Antarctic Ice Sheet). Ice fields are a large region of ice that does not overwhelm the local topography (and are smaller than 55,000 km²). Ice caps are dome-shaped ice masses with radial flow. Outlet Glaciers flow from an ice sheet, ice cap or ice field, and typically follow topographic depressions. A Valley glacier, instead, has a clearly-defined accumulation area and is limited by topography, following a pre-existing valley.

Mountain Glacier includes cirque, niche or hanging glacier, and are generally adhering to valley sides. They can include cirque glaciers, which are located in an armchair-shaped bedrock hollow, and have no glacier tongue; niche glaciers, developed in small couloirs or depressions; or crater glaciers, in volcanic craters.

Glacieret or snowfield is smaller still, with very small ice masses, virtually no ice movement, and accumulation and ablation areas not always detectable. Ice shelves are floating masses of ice fed by tributary glaciers. They are attached to the coast, and are nourished by snow fall, bottom freezing and influx of glacier ice. Rock glaciers are where the ratio of rock to ice favours more rock than ice. This is a feature with movement downslope of debris with interstitial ice. Finally, ice streams are part of an ice sheet where the ice velocity is higher than the surrounding ice mass (for example, Pine Island Glacier).  Photographs of all of these phenomena are provided in the illustrated Glaciers-Online photo glossary.

Glaciers can also be characterised by their thermal regime – see Glacial Processes.

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