Next message: George Huxtable: "Re: on finding Pitcairn Island"
Trevor,
I think that for the most part a wave will not feel the bottom until the
depth of water is less then ½ of the wavelength. At that point you will
begin to see some difference in the wave pattern.
All the best,
Robert Gainer
>From: "Trevor J. Kenchington" <>
>Reply-To: Navigation Mailing List <>
>To:
>Subject: Re: on finding Pitcairn Island
>Date: Tue, 21 Sep 2004 11:45:56 +0000
>
>Peter Fogg wrote:
>
>>What is found between New Zealand and Australia are a number of underwater
>>sea mounts, mountains
>>that rise from the sea floor about 4000 metres below to within a
>>comparitively short distance, some of
>>them, from the surface. When the sea is agitated the area above the mounts
>>has a different characterisitic
>>compared to the open ocean, and could lead to speculation; such as land
>>being near.
>
>
>Could Peter elaborate on his sources for the contention that the sea
>surface gets a detectably different "characteristic" above a seamount?
>
>I have a very little experience fishing over seamounts in the general
>area in question, though rather further south (around 49 degrees
>latitude). We certainly had times down there when the sea was agitated,
>as would be expected, but nothing that suggested to me that land was
>anywhere near. [In my case, the summits of the seamounts were around 700
>metres depth. They stand on the South Tasman Rise at around 1400, while
>the surrounding area is 4000 metres or so in depth. Clearly, a seamount
>which comes very much closer to the surface would be more likely to have
>effects visible to a surface observer.]
>
>Of course, we had SatNav and charts to tell us that land wasn't close,
>plus a powerful sounder to tell us just how deep the water was, and thus
>were not looking for subtle signs. Add in an enclosed wheelhouse and
>work to do that kept me from watching the sea all day long: Maybe there
>were features in the wave patterns that a sailing-ship master, running
>his easting down across the same area, would have observed.
>
>
>Trevor Kenchington
>
>
>--
>Trevor J. Kenchington PhD
>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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