Antarctic Ice & Antarctic Glaciers

Antarctica is 99,6% covered in ice, and contains 90% of all ice on the planet. Antarctic ice thus accounts for more than 80% of all fresh water on earth. Not just the size, but the age of Antarctic ice is vital to science.

The amazing Antarctic water cycle

Water from the sea, evaporates into clouds, the clouds move over the continent and the water falls in the form of snow. That snow is then compacted into the icesheets, which in turn move toward the coast and in the form of glaciers and eventually become iceshelves. When pieces break off the iceshelf (icebeargs) and melt the water once again returns to the sea. Hence after tens of thousands of years the cycle is complete.

Types of ice found in Antarctica

Glaciers / Icesheets / Iceshelves
According to The Encyclopædia Britannica* a Glacier is "any large mass of perennial ice that originates on land by the recrystallization of snow or other forms of solid precipitation and that shows evidence of past or present flow. A glacier occupying an extensive tract of relatively level land and exhibiting flow from the centre outward is commonly called an ice sheet."

Hence, Icesheets are larger slabs of ice that consist of snow that has accumulated and compacted over millions of years to form hard ice. When these icesheets reach and extend into the sea the floating part is termed an Iceshelf. Icesheets can be extremely thick (>4700m in places), and form the bulk of Antarctica's ice. Iceshelves are between a few meters to several hundred meters in height. Most of the ice below the sea and thus not visible.
Since most of the Icesheets are resting on top of solid ground, the ice tends to move under the influence of gravity. A lot of research into glaciers is undertaken in Antarctica using people on the ice during summer as well as sophisticated satellites all year round.

See the Climate History section below of details of the secrets that Icesheets and Glaciers keep, and the efforts Scientists are doing to learn them.

Icebergs
Icebergs are pieces of Iceshelf that have calved (broken off) from the rest of the self. This is natures way of returning water to the ocean from within Antarctica.

Sea ice / Pack ice
During the winter months, the sea freezes over forming sea ice. (Because the sea is saline (Salty) it freezes at about -1.8C, not zero.) In some places, like off Dronning Maud Land, the sea ice extends to over 1000km from the edge of the iceshelves. In spring when the ice starts to break up if breaks into pieces with are called pack ice. These pieces vary in size and shape, eventually melt away until the next season.

Pancake ice
When the sea starts to freeze over in early autumn, the freezing sea forms patterns that look like pancakes floating on the water.

Ice / Glaciology Terminology

Accumulation Snow, of other material added to glacier or ice sheet through precipitation.

Accumulation Zone The area of the glacier or ice sheet where the accumulation exceeds the loss (ablation) takes place. (The area where there is a nett gain in glacial mass.) Usually situated near the top of the glacier or ice sheet.

Ablation The process of by which glaciers or ice sheets loose mass, through melting, evaporation, or the calving of icebergs at the sea). In Antarctica, most ablation occurs by calving.

Ablation Zone The area of the glaciers loose more mass than gain. In Antarctica, the ablation zone for most glaciers is very small, and typically at the edge where icebergs form.

Equilibrium Line
The line / area where there is not nett gain of glacial mass and hence where the accumulation zone and the ablation zone meet.

Glacier terminus
The edge of the glacier, also known as the nose, or snout. This is most commonly seen in Antarctic in the form of the edge of the Iceshelf.

Grounding Line
When the glaciers and icesheets reach and extend over a lake (e.g. Lake Vostok) or the sea, and start to float, the line where they loose / gain contact with solid ground is called a Grounding Line of Grounding Zone.

Climate Change and Climate History

When a snow flake falls it contains important information about the atmosphere in which it was formed, thus by studying ancient snowflakes glaciologists can determine what the atmosphere was like thousands of years ago.

Collecting ancient snowflakes is done through a process called Ice Core drilling. By drilling into and extracting samples from inside the ice, scientists are able to study these compressed snowflakes. The compression in these glaciers is so great that the ice turns blue in colour. This color is due to the fact that all air has been compressed out of the ice due to the enormous pressure.

By analysing these samples scientists are able to plot and study long term temperature and other climatic and atmospheric trends. They are even able to detect events that produce detectable materials like volcanoes, nuclear explosions, and other data that help in syncronising data collected with known events in the past.

The deepest core drilled thus far is by the Russians at Vostok Station, where they have drilled (with great skill) to a distance of over 3600m. It is estimated that the ice removed from that depth is over 400 000 years old.

Dating (determining the age of) the ice is a crucial part of the entire research process, and it is one about which there is much discusion. Since there is no single optimum way to determing the age of the ice removed there is some room for error and interpretation, which can lead to conflicting theories or assumptions.

Pollution

As mentioned before snowflakes trap and store vital information about the atmosphere when they are formed. Thus by collecting and studying this data scientists are able to detect and analyse pollution in the atmosphere, just like they are able to detect volcanic or nuclear activity.