At the beginning of the harsh and brutal winter starting around March,

the loose pack ice that has spent the summer months circling Antarctica

begins to drift up northwards.  Pack ice is old sea-ice, it is frozen sea water

that is about a year old or more, it froze and formed elsewhere and

then later floated off with the winds and currents.

Does pack ice affect shipping

This is pack-ice in the summer months

around the Antarctic peninsula.   The ice looks fairly continuous,

but has quite a lot of open water

between the pieces and so can be relatively

easily pushed aside by an ice-strengthened ship, in this

case HMS Endurance. Larger pieces such as this one that are hit by

the bow of the ship crack up into smaller pieces.  

Does pack ice affect shipping

 Proper Ice breakers have rounded

hulls and rounded bows rather than being sharp and pointed.

When breaking through very thick ice, the front of the ship rides up

over the ice and the weight of the ship breaks through.

Passage is slow though, and heavy on fuel,

but most of all, it takes an experienced and well informed ice-

pilot to be confident in entering such ice so

as not to be locked into the pack should the wind direction change

and consolidate the ice.

Arctic ice formed much earlier than previous estimates: study        

Prehistoric geological records from the frigid vault of the Arctic

Ocean haveshown that glaciers

were formed in the Arctic Ocean about 45 million

years ago, 14 million years earlier

than geologists had thought, scientists reported on Wednesday.

evidence, pea-sized pebbles locked inside a

430 meter-long sediment core,

also indicates that the immense sheets of ice at the

Earth's two poles formed almost

simultaneously. Earlier, geologists had believed that

glaciers had formed in Antarctica long before they appeared in the

Arctic.

Snow and Ice - The Frozen Continent

Some people have considered towing icebergs from Antarctica to parts of the world in need of fresh water.As strange as it sounds, however, Antarctica is essentially a desert. The average yearly total precipitation is about two inches. So, where did all this snow and ice come from? The answer lies in Antarctica's unique location at the bottom of the world and the unique weather conditions that exist there.

Snow and Ice - The Frozen Continent

With 98% of its surface covered with various forms of snow and ice, it's no wonder that the continent of Antarctica attracts "cold weather" scientists from all over the world. Basically, Antarctica is a snow and ice "factory" with ice depths on the Polar Plateau reaching 15,000 feet (the continent's average ice thickness is 7,000 feet). Thus, one of Antarctica's most important resources is its ice. It is said that Antarctica's ice accounts for 70% of the world's fresh water.

IceSheets Vast shields of thick continental ice that have formed through the accumulation of snow over millions of years.

Icebergs Chunks of ice of all sizes which break off continental ice sheets and ice shelves in a process known as "calving". Individual icebergs range from a few meters to tens of miles in diameter.

Ice Crystals Also known as "Diamond Dust," ice crystals are essentially crystallized water vapor, found in areas of low humidity and extreme cold.

The Many Forms of Snow and Ice

Storms cannot penetrate far into the continental

interior except in the low lying regions. Most snow fall occurs in winter when

the westerlies are strongest and the storm

systems can reach inland farther and more often.

When warm moist air does make it all the way to the

Polar Plateau, the air cools considerably. Eventually it becomes supersaturated

with ice crystals.

Where does snow come from?

Where does the snow come from?

The precipitation is carried in by the storm systems. These cyclonic systems carry warm moist air from the lower

latitudes. So, most of the snow falls within 120 to 190 miles of the coast. Average precipitation on the coast is 20 to 50 inches of snow (7 to 16 inches of water equivalent). The

Antarctic Peninsula has highest precipitation of the continent, (36 inches water equivalent).

IceThe oldest ice we have encountered is "green ice." This ice, easily spotted

amongst the younger lighter ice, appears dark green from the great pressure during the thousands of years of compaction. When ice surrounds the boat, only once in a great while will we see green ice; more often we see

blue and white ice. While in the glaciers blue ice underwent some compaction before it caved into the sea, and white ice is newly formed

within the past few years.Some bergs are known to float in these waters for years before totally

melting away into the cold. Tabular bergs, bergs which look like blocks of wood, are formed when glaciers extend over the sea and break.

http://www.coolantarctica.com/Antarctica%20fact%20file/antarctica%20environment/seaice%20formation.htm http://english.people.com.cn/200606/01/eng20060601_270299.html

http://www.antarcticconnection.com/antarctic/weather/snow-ice.shtml

http://mt.middlebury.edu/middblogs/ddums/antarctica/2005/04/ice_1.html

http://www.globalclassroom.org/antarct4.html

http://library.thinkquest.org/CR0215022/timeline.htm

http://www.purdue.edu/UNS/html4ever/2004/041227.Huber.Antarctica.html