Re: Does the arctic ice cap ever melt completely?

Message ID#: 887710879.Es 

Does the arctic ice cap ever melt completely? 

I think we need to get our terms straight. In your message line you wrote 
"Does the arctic ice cap ever melt completely?" but in the body of your 
question you said "if the South Pole never melts completely how much does 
it melt?"

The Arctic is the North Pole; the South Pole is Antarctica. I suppose you 
are really interested in the South Pole but I'll give you a brief summary 
for both. Remember also that the North Pole is in the Arctic Ocean (or sea) 
whereas the South Pole is on solid land.

For starters, the term "sea ice" applies to any kind of ice formed in the 
ocean.  There are basically three kinds of sea ice: polar ice, pack ice and 
fast ice.

The arctic ice cap (the area around the North Pole) stays partially to 
totally frozen year round with what is known as "polar ice." This can 
achieve thicknesses in excess of 160 feet but averages only 6.5 feet in 
summer.  

Outside of the polar ice (at lower latitudes) is a region of seasonal ice 
buildup.  This ice is called "pack ice." During summer, although lots of 
melting and break up occurs, this area still contains significant amounts 
of free-floating pack ice and icebergs also remain.  During wintertime, 
pack ice has a maximum thickness of about 6.5 feet. 

Pack ice is somewhat mobile even in winter. It fractures and moves around, 
sometimes piling up into thick accumulations along the edges of the polar 
ice, increasing its area. In winter it is still possible for specially 
equipped ships, "called ice-breakers," to move through pack ice.  

At even lower latitudes next to land there is yet another kind of ice.  
This is called "fast ice" because it is held "fast" to the shore.  It can 
grow to thicknesses greater than 6.5 feet during winter, but disappears 
during summer.

On the other hand, ice more-or-less permanently covers 98% of the land area 
in Antarctica.  There are minor areas (= 2% of the land surface) with no 
ice or snow (called "dry valleys") but there are also places with over two 
miles of ice in the form of glaciers.  Glacial ice is highly compacted  and 
flows easily due to the weight of the overlying ice.  When glacial ice 
flows off of the land and into the ocean (known as "calving") an iceberg is 
produced. 

Along some areas of Antartica's coastline there is a permanent ice margin, 
sort of an apron, called an "shelf ice." Ice on the ice shelves is thick 
enough that in some places it is resting on the sea bottom and supporting 
its own weight.  Much of this shelf ice is actually calved from the land 
and so is not true sea ice.

Other than the shelf ice, the rest of the sea ice in the so-called Southern 
Ocean around Antarctica is rather seasonal.  It consists of pack ice and 
fast ice, both of which melt and break up during the summer.  You might 
wonder why, if it is so cold there, the sea ice breaks up more completely 
around Antarctica than around the Arctic Sea.  This is primarily due to the 
powerful winds that blow around Antarctica, causing the sea ice to break up 
and preventing a greater pack ice buildup.