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    Re: Big Full Moon and Perigee Spring Tides
    From: John Huth
    Date: 2011 Mar 20, 17:47 -0400
    Frank - 

    Now that you mention it, maybe you could help me with with some terminology.

    I'd thought that what you describe is the 'age of the tide', while the difference between the meridian passage of the moon and high tide is what we call 'tide lag'.   Is this incorrect?

    A curious effect on what I'm calling lag:  in Boston Harbor, the high tide is nearly coincident with the meridian passage of the moon, while in Newport Rhode Island, it's nearly coincident with low tide.   The latter has to do with the way the ebb and flood fills both Long Island Sound and Nantucket Sound/Buzzard's Bay.

    As long as we're on tides, here's something curious I stumbled upon.   In 1906, while exploring Axel Heiberg Island, Peary thought he saw land out in the ice pack.   He named it Crocker Land and put it around 83 N, 100 W.    

    In 1911, a guy named Rollin Arthur Harris published a book, titled Arctic Tides (Robert Eno's post reminded me of this).   Harris presented an exhaustive compilation of data on tides in the Arctic Ocean from various sources, Peary included.   In his analysis, Harris concluded that the pattern of tides and currents in the Arctic basin could only be explained by the presence of a huge land-mass in the unexplored regions of the basin.       

    It turns out Crocker Land is on top of 3500 of ocean - a mirage.   


    John H. 

    On Sun, Mar 20, 2011 at 7:22 AM, Frank Reed <FrankReed{at}historicalatlas.com> wrote:

    John H, you wrote:
    "I'm at Cape Cod today, and we do have some big tides today, so that much is interesting."

    Also note that there is a lag of about a day for Spring Tides on the Atlantic coast of the US. The ocean tides are like a big set of coupled, driven harmonic oscillators. The driving force has numerous frequencies. The most important frequencies, of course, are the daily rates for the Sun and the Moon to pass over any point on the Earth. Since they're different frequencies, they generate different responses in the driven oscillators with slightly different phases. That yields the delay in the Spring Tides. This delay is different in different parts of the world. As I said, here on the Atlantic coast of the US, it's about a day. In northwest Europe, two days or more. On the Pacific coast of the US, close to zero, and there are even a few spots around the globe where the Spring Tides lead the phase of the Moon by a couple of days. This lag was one of the first things that I brought up on NavList way back in December of 2003. I was interested because early editions of Bowditch still described European conditions and back then there were ZERO 19th century editions of Bowditch available online. Now there are dozens.

    -FER


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