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> Walking on the Arctic Ocean, Walking on the Arctic Ocean
post Sep 14 2005, 07:50 PM
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how can you tell the age of the ice?
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post Sep 16 2005, 05:32 PM
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Bruce is one of my good friends on the ship and Sea Ice Researcher from
Cold Regions Research and Engineering Laboratory. He answers Ray's question.

Sea water is around 32 ppt (Parts per thousand) salinity.
When sea ice first grows it is dark gray and the salinity of the ice is around 15 ppt.
As the ice gets older the salts in the ice drain out from it especially in the summer time when the ice warms up. Therefore ice that has been through a summer melting period will have salinities of 8ppt or less. Due to the loss of the salt, the older ice apears more blue. There is no way to know exactly whether ice is 1,2,3or more years old.
We can only say that the ice is "new ice" ice that has just formed and is thin, "First year ice" ice that is usually less than 2meters thick and is still quite salty, or that it is "multi-year ice" which is ice that has survived one or more summer melt seasonss. Multi-year ice starts off the freezing season with some thickness such that it grows even thicker over the winter. (2-5meters thick) Therfore if the ice is >2meters thick it is probably mulit-year ice. We use a combination of these basic observations to estimate the age of the ice but there is no way to know exactly how old it is, just an educated guess.

Bruce Elder
Sea Ice Researcher
Cold Regions Research and Engineering Laboratory.
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