Hello,
having read the message by Andrew Taylor I just want to communicate a short
comment on the reduced tidal variation caused by land. I realize this posting
comes quite far from the topic of birding-aus but I thought it might have some
interest to you considering the recent discussion on tides.
I live here in Finland on the shores of the Baltic Sea which has many
peculiarities because of the geography as some of you probably know (reduced
salinity causing quite low species diversity etc.). One of these strange things
is the virtual lack of any tidal variation even though the Baltic is connected
to the North Sea. The waterway connecting the Baltic to the ocean is very
narrow and shallow which reduces tidal variation to only a couple of
centimetres (I´m not aware of the exact figures as this is not my expertise).
So, main fluctuations in the sea level are caused by atmospheric pressure
gradients and not by tides. However, in extreme cases these fluctuations can
have serious consequences as the changes in sea level can reach even several
metres in the St.Petersburg region. This is the reason why Russians are
building the dam to protect St.Petersburg (or at least were, I´m not sure of
the current situation as the dam will / would have some vey unpleasant
consequences itself)...
Cheers,
Turkka Korvenpää
Finland
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