Re: [Paddlewise] Fresh water vs. seawater for cooking?

Philip Torrens wrote:

> I have not tried this myself, but I've read that as sea-ice melts, the
> saltier areas melt first(think of salt scattered on an icy road), so that
> older ice that has been melted and frozen a few times becomes purer and
> purer. It supposedly can be identified because the near "fresh" stuff is
> clear and blue; the salty areas are milky white.

Digging back to my ice mechanics research days*:

As I understand it, you don't need a thaw cycle to desalinate the ice.  When sea
ice forms, it forms in long thin crystals that are oriented vertically.  These look
like the crystals in a Popsicle that radiate out from the centre.

The ice isn't particularly strong and the voids between the crystals contains salt
water and some air.  As time goes by, some of the salt water in the voids drains
out and the rest freezes and connects the existing ice crystals into a consolidated
mass.  The elimination of voids, which gave the ice its white appearance, results
in dark, clear, black ice.  You can tell the age of sea ice in aerial and satellite
photographs from its color.  The ice that results has a lower salt level than new ice
with water in the voids.  It is also somewhat stronger.

So if you want to cook with sea ice, take the clearest stuff.  If you want to ram it
with your kayak, choose the white stuff.

Mike

*I worked for a company that would do towing tank tests of icebreakers and stuff.
The whole room was kept below freezing most of the time and they'd grow the
ice cover to the thickness required for a test.  It always amazed me that the crystals
always grew vertically.    Most of my research was on artificial islands and oil exploration
platforms in the Arctic (Beaufort Sea).   I got stuck working with artificial ice, made
of a urea compound and wax mix.   Not as much fun, but a lot warmer.  We were about the
only people in Ottawa that wore parkas in July.

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