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Interesting original question from Paul, so I looked it up in (where
else but?) Wikipedia -> sea level -> mean sea level (MSL), where
there's a readable but somewhat technical explanation. Conceptually,
MSL is defined apparently by a 3-dimensional imaginary geometric
surface hovering around the earth, a geoid, at which sea level would
equilibrate if there were no variations in air pressure etc, but from
which there are real departures of up to +/- 2 meters. It also says
that an ellipsoid surface is easier to model than a geoid in order to
tie into the GPS system for aircraft navigation, for aviators who wish
to land on aircraft carriers, etc, and is increasingly used. Changes
in MSL over geological time are also covered a bit.
The article also mentions apparent changes in sea level caused by
land sinking or rising locally, but you'd need to look elsewhere for
specifics. I also thought that NS overall was still rebounding slowly
from the oppressive weight of the last ice age, but it would need a
geologist to tell us whether such changes are bigger or smaller than
the projected rise in overall sea level caused by such things as
current and future melting of ice on land, and sea water warming.
Steve, Halifax
On 7-Mar-07, at 1:34 PM, Gerald Ruderman wrote:
> Heather Drope wrote:
> . . . .
>> I have heard that the province is sinking and the oceans are
>> raising. If
>> that is the case I wonder what they do then about their bench
>> marks?Will
>> they be adjusted or is this something we don't have to worry about in
>> my
>> generation. Heather
>
> Sinking! I thought it was still springing back up after being pushed
> down during the ice age. I do agree about the oceans rising.
>
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