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    Re: New Moon, Perigee, and Solstice
    From: Trevor Kenchington
    Date: 2003 Dec 24, 21:16 +0000

    While I am pointing out errors, your earlier message supplied a few. You
    Reed wrote:
     > Trevor K you wrote:
     > "On the effects of a tidal barrage at the head of Fundy: I'm not sure
     > that anyone really knows what it would do to amplitudes elsewhere."
     > Then you would be pleasantly surprised. These calculations were do-able
     > even thirty or forty years ago.
    I wasn't around here when Fundy tidal power was being seriously
    considered but I was in England for the parallel debates on a tidal
    barrage in the Severn Estuary. That would have been circa 1975, hence
    some 30 years ago. Very clearly, the calculations were NOT "do-able".
    Among the rage of answers produced would that there would only be a
    negligible increase in tidal range as close as Milford Haven and that
    there would be a major increase as far away as Liverpool. I really doubt
    that the estimates for the proposed Fundy project were any more precise.
    Nor am I aware that anyone has made such estimations subsequently. I
    have some passing involvement with the tidal modellers at the Bedford
    Institute of Oceanography who, with colleagues in New England, have gone
    far to understand the Fundy/Gulf of Maine/Georges Bank tidal system. (I
    work on a number of fisheries situated in that region.) I have not heard
    any of them speak on the topic of alterations to the tides that would be
    caused by anthropogenic changes in basin morphology.
    You continued:
     > And:
     > " I can say that the marine geologists here have recently found active
     > erosion
     > of the seabed in the Bay. One possible explanation is that the system is
     > gradually getting nearer to perfect resonance with the semi-diurnal
     > lunar tide (the likely cause being isostatic rebound, which is lifting
     > the New Brunswick side of the bay, while dipping the Atlantic coast
     > of Nova Scotia into the sea -- though the blockage of various tidal
     > rivers by road causeways might be contributing)."
     > Also, don't forget that the tides themselves are a massive force of
     > erosion. A situation like the Bay of Fundy does not last long on a
     > geological time scale.
    The sedimentologists who are studying this issue seem confident that the
    seabed would be in equilibrium with the existing tidal streams, if those
    were themselves steady and if human actions did not disturb the balance.
     > The tides will slice right through that isthmus
     > in New Brunswick (?? pardon my ignorance of Canadian province
     > boundaries) in a few thousand years.
    Hardly. New Brunswick is rising out of the ocean quite quickly. Unless
    the ice caps hurry up and melt, raising sea level even faster than the
    land is rising, the Tantramar marshes are more likely to dry up than get
    eroded away. Anyway, tidal streams at the head of a narrow embayment are
    necessarily negligible: there is nowhere for the water to go once it
    reaches the head of the bay. Unless someone cuts a canal through, or the
    sea rises enough to flood over the top, there isn't any flow to slice
    through anything.
     > Seabed biota.... Drool....  I love that stuff. Do you get Limulus
     > (horseshoe crabs) up there?
    I think you will find that Limulus peters out north of Cape Cod. I have
    a vague memory of it being recorded off Nova Scotia but it certainly
    isn't normally found here.
    Trevor Kenchington
    Trevor J. Kenchington PhD                         Gadus{at}iStar.ca
    Gadus Associates,                                 Office(902) 889-9250
    R.R.#1, Musquodoboit Harbour,                     Fax   (902) 889-9251
    Nova Scotia  B0J 2L0, CANADA                      Home  (902) 889-3555
                          Science Serving the Fisheries

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