Everything you ever wanted to know about ICE but were afraid to ask
1. What is SEA ICE and what does SEA ICE look like?
Sea ice is a thin, fragile, solid layer that forms in the Polar Oceans. It forms a boundary between the relatively warm ocean and the cooler atmosphere. There are many
different kinds of sea ice, and here are a few of the main ones:
This is a picture of a first year ice floe, or ice that grows during one winter. It is usually smooth and is commonly 0.5 to 1.0 m thick. The ice has been
broken up to form rafts. A research ship is in the left corner.
Ridges are long extents of compressed, broken pieces
of first year ice. Their thicknesses can vary greatly.
Multi-year ice has grown during at least
two consecutive winters and is 3 to 5 m thick. It is not as smooth as first-year ice. A weathered ridge crosses this floe.
2. Why does SEA ICE float?
Sea ice floats because it is less dense in the solid phase than it is in the
liquid phase. If sea ice were MORE dense in the solid phase, it would sink
to the bottom of the ocean (light things can't carry heavy things too well,
right? Sinking, dense ice would cause the oceans to freeze to their beds, so animals and
plants which live on the ocean floor would die!
3. How does the structure of SEA ICE help it to float?
Sea ice is made of oxygen atoms and hydrogen atoms that are joined together
like a net. Hydrogen bonding gives ice all of its unusual
properties. As ice melts, hydrogen bonds are broken. The molecules become
more closely packed, or more DENSE. This is why ice can float on water!
4. Where can I find some SEA ICE?
Sea ice is found in the North (Arctic) and South (Antarctic) Polar regions.
In the Arctic, there is a permanent body of ice.
5. Is SEA ICE the same thing as ICEBERGS?
No way! Icebergs are broken pieces of glaciers which originate from
masses of snowfall on land. Here is a shuttle picture
of the Malaspina Glacier in Alaska:
Glaciers carry sediment around with them as they move, and these sediments
can be studied to determine where the glacier or iceberg originated.
This is a dirty iceberg in the Weddell Sea, which is east of the Antarctic
Peninsula. For more on glaciers, click
here.
6. Why isn't SEA ICE very salty? Could I eat it for breakfast?
Well, along with a balanced diet of toast, juice, and milk, sure! It is
about as salty as the ice in your refrigerator! Although sea ice is made from
salty sea water, the salt molecules are rejected back into the liquid as
ice forms. There isn't much room for salt molecules to be trapped in the
close-knit structure of sea ice. And as far as breakfast goes, there's even
a kind of ice called Pancake Ice, which are small (1-3 m in diameter) and formed when slushy ice is clumped together by ocean wave action:
7. What is it about SEA ICE that we want to measure?
The oceanic processes of greatest significance in the Polar seas
are those related to the presence of ice and include its thickness, compactness
and type, its motion, the presence and energetics of ice-margin phenomena such
as bands and eddies, and the penetration of oceanic swell into the ice pack.
Thus, scientists use the SAR images to measure ice concentration, ice type,
ice motion, ice thickness, and ice margin structure.
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