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    Currents & Streams, was: DR thread from Nov-Dec '04
    From: Trevor Kenchington
    Date: 2005 Jan 24, 09:11 -0400

    Jared,
    
    You have completely missed my point.
    
    The horizontal water movement associated with the tides is correctly
    termed the "tidal stream", and specifically _not_ a "current" of any
    kind. That was correct usage historically [though if you go all the way
    back to the 1850s, this movement was just called "tide" (though still
    explicitly not "current") and "stream" meant the fast-moving core of any
    horizontal flow]. It remains the correct usage in Britain, Canada and, I
    would guess, most of the English-speaking world, even though the
    ignorant often speak of "tidal current".
    
    U.S. English is, as so often, different. "Tidal current" has gone from
    being a neologism into being the accepted term. Bowditch (1995) and the
    NOS glossary both recognize only "tidal current" as U.S. usage, while
    also noting the British use of "tidal stream". I _think_ I have seen
    earlier U.S. authorities note the common use of "tidal current" while
    also acknowledging that "tidal stream" is correct. However, I
    immediately cannot place my hand on an example.
    
    So once again, if we are being pedantic, the term is "tidal stream".
    
    
    
    As to your "Slack tide and slack current usually do not coincide,
    either": As I have pointed out before, the term is "slack water" (and on
    that one, U.S. and British usage agree). The phenomenon that, I suspect,
    you are meaning by "slack tide" is the moment when the rising tide stops
    momentarily before beginning to go down again (or vice versa). If so,
    that is the "stand of tide" and not a "slack" of any kind.
    
    But you are right that slack water and the stand of tide do not usually
    exactly coincide. They would if the tides were perfect standing waves
    (and if there were no freshwater outflows to confuse things). They must
    at the heads of inlets (again, if no freshwater flow). But the closer
    that the tides get to a perfect progressive wave, the further out of
    phase the stream and the vertical movement get, until (as in a
    deep-water swell) they are 90 degrees out.
    
    
    Trevor Kenchington
    
    
    You wrote:
    
    > Trevor-
    >   are defined to be more-or-less steady flows.>
    >
    >  Currents are steady? I have to disagree. In coastal areas, the currents of
    > most concern are often tidal currents, as basins and inlets fill then
    > discharge with the rise and fall of the tide. Shinnecock Inlet, Jones Inlet,
    > the entire body of Long Island Sound, all are subject to Tidal Currents and
    > NOAA even published/es a Tidal Current chart set for mariners, so they can
    > figure out the local currents based on the state of the tide. Slack tide and
    > slack current usually do not coincide, either.
    >
    >  Ocean currents may be steady--but not "currents" aren't exclusive to
    > bluewater sailors.
    >
    
    
    --
    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
                          http://home.istar.ca/~gadus
    
    
    

       
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