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Hi Steve & All, Mar 7, 2007
There is an article (perhaps a bit out of date) on Maritime
submergence in Proc. N.S. Inst. Sci 27, Supplement 3, 83-102, 1975 by D.
R. Grant. In round numbers, the rate of sea level rise in N.S. over the
last 5000 years, relative to land, has been constant at about 1 foot per
century. Having rebounded after glacial retreat we appear to have
started going down about 9000 years BP.
One must read some figures and text with care because metric
measurements are sometimes out by an order of magnitude (e.g. cm when dm
was intended on p. 97 and mm when cm was intended on p. 88) but all in
all a very good article I think.
Yt, Dave Webster, Kentville
Steve Shaw wrote:
> For detailed discussion of land sinking/rising, and of determining
> actual mean sea level (MSL) changes over time as a result of
> measurements that largely originate from multiple tide gauges, try
> this (1995) review:
>
> http://www.agu.org/revgeophys/dougla01/node3.html
>
> According to this site, local sea level is rising rapidly by 3.5 mm
> per year near Baltimore because the local land is sinking. Because of
> a sort of amplification effect explained in the article, a change of 1
> mm can result in devastating effects 50-200 times larger, as has
> happened in nearby Chesapeake Bay. Oppositely, local sea level is
> falling rapidly by 4 mm per year at Stockholm because of continuing
> post-glacial rebound (the land is rising after a heavy ice-age
> load). Nothing is mentioned in the article on the situation further
> north from Baltimore in NS, but presumably NS is more like Sweden.
> The more reliable tide gauge data are said to indicate a rise of 1.8
> mm per year in MSL, averaged worldwide. At least in 1995, this guy
> seemed to think this rate of rise was not obviously accelerating, but
> I suspect that this conclusion may be out of date.
>
> On 7-Mar-07, at 3:52 PM, Gerald Ruderman wrote:
>
>> Paul,
>> I am curious where you learned that GPS uses atmospheric pressure for
>> altitude.
>>
>> My GPS gives me altitude when it has good signals from 4 satellites.
>> When it only has 3 it only give me position on the geoid. GPS receivers
>> have no way to send anything to the satellites.
>>
>> Atmospheric pressure is important at airports because planes most basic
>> altitude measurement is by pressure.
>> Gerald
>
>
>
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