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Icebergs 1
Icebergs 2

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1/ How can this man stand next to an iceberg?
Ice-bergs drift around the Southern Ocean carried by the currents and blown by the winds.

In the winter the sea-ice freezes around them and effectively glues them in place until the spring when the ice breaks up and they can begin to move again.

During this frozen-in time, it is possible to travel out across the sea-ice and walk right up to the bergs.

 

 

2/ Why does the iceberg look different when the sun shines?
It can be quite magical standing next to an ice-berg, especially when the sun is shining and glistening off the ice.

The sun can also penetrate the ice and be reflected off inner surfaces giving a whole variety of effects and colours from white through a range of vivid blues, quite an unreal experience.

 

 

 

3/ How big is the "tip of the iceberg"
The tip of the "ice-berg." Everybody knows that most of an iceberg lies under the water, but most don't know that the amount beneath the surface varies from about 50% to 99%.

The cause of the variation is largely in the amount of air that is trapped in the ice so affecting its buoyancy. An average iceberg will be about 80-90% beneath the surface. Very low lying pieces of ice of whatever size in the water are known as "growlers". These often have a green tinge to them. They are known as growlers because they present a particular hazard to shipping with the small amount visible above the water and the dark colour making them especially difficult to see and therefore especially dangerous.

4/ When is an iceberg not an iceberg?
There are lots of different names for different kinds of ice. Large pieces of ice that were once part of an iceberg that broke up are known as "bergy bits" if they are too small to be considered as icebergs themselves (I never did discover when a "bergy bit" was big enough to be a "berg", I think it's a matter of opinion!).  

These bergy bits in the picture are trapped in the frozen sea-ice in the winter making it possible to walk out to them. In the distance can be seen trapped icebergs and the long low landmass of a nearby island, the two peaks to the left are about 40 miles (64 kilometers) way.

 

 

5/ How are icebergs made?

Icebergs are made of freshwater ice and not of frozen sea water. They form from the edge of glaciers when the glacier reaches the sea and either breaks off in pieces to form an iceberg, or in the case of an ice shelf, begin to float on the sea and then breaks off from the rest of the glacier as a large slab.

Icebergs are made up of snow that has fallen over many hundreds or even thousands of years. The stripes and different coloured layers in icebergs represent different layers of snowfall and the weather conditions under which the snow fell. If it is very cold then a light open layer with much air included will be formed, this gives a paler or white layer. The darker, bluer layers come from snow fall in relatively warm, maybe even wet conditions when little or no air is trapped in the layer.

In addition to this, air is squeezed out of the lower layers of a glacier as more and more snow falls and so the weight of snow builds up.

6/ Are you sure this thing's safe?
Standing next to an iceberg such as this one can be quite a scary experience. In addition to being stuck in the sea ice, this particular berg has been grounded on the sea bed. It was probably blown towards shore by strong winds or a storm, and on a high tide. When the wind died down and the tide fell, the berg was left resting, stuck on the sea bed.  

A result of this is that when the tide rises and falls the sea ice rises and falls with it but the iceberg doesn't. There are all kinds of creaking and groaning noises made by the sea ice as it is forced to rub up and down the uneven sides of the berg with the tide. To add to these unsettling sounds are an assortment of creaks, groans and bangs made by the iceberg above water as the sun heats up the surface.

The fear is that either a large lump of ice will come tumbling down or worse still, the iceberg becomes unstable and tips up to a new more stable position. This tipping up rarely happens in the winter, more commonly it takes place in warmer summer temperatures, but it is not unknown and if it happens can cause waves and ripples that break up the surface of the sea ice for miles around. Neither of these events are ones that you want to witness while standing on the sea ice surrounding the iceberg!

Icebergs 2   Antarctica Fact File Index


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