Low Tide expands the “Public Trust” area:
Use our tide calendar to help plan your beach visits

October 2018.JPG

Download Calendar

 

Among the most important issues we will confront through our site, is to educate the dog guardian community— AND the non-dog guardian community at-large— about the Public Trust Doctrine, and how it impacts beach access at Town of Fairfield beaches. 

This has been a major focus of our efforts and critical to our guiding mission since we decided to form a group of responsible dog guardians coalesced around this issue.  We can't plan the tides, of course; but if convenient, it can be advantageous to visit the beach at low tide, since this expands the Public Trust area considerably: sometimes by hundreds of feet laterally.  Since the leash requirement (at all beaches other than Jennings Beach) is not enforceable in this area, it provides significantly more space to responsibly walk or exercise with your dog.

 


In order to support and maintain long-term stability in Fairfield's beach access metrics, it is critical to represent the dog guardian community positively, and as such, important to understand the doctrine and concepts of what constitutes legitimate and reasonable public access.  We encourage you to review our essay on this topic, and invite your participation
in the dialog.

 

Public Trust area available to us for walking with our dogs is the result of gravitational forces of the moon (augmented by the sun);— and conjoined with effects of the earth's rotation and the bathymetry[1] of the ocean. 

What we know as high tides are “tidal bulges” which occur simultaneously on opposite sides of the earth.  As the earth rotates on its own axis the tidal bulges wash back and forth causing us to perceive high and low tides. 

The daily pattern holds about six hours between high and low tide, with generally two high tides and two low tides every 25 (24.84) hours.[2] 

As the moon orbits the earth, its gravitational pull is intensified (or challenged) by the pull from the sun: when the moon is pulling at an angle to the sun, the tidal bulges are weak (small); when the two are aligned, that force is increased, and the bulges are more forceful (a higher or lower tide).   This produces the monthly pattern[3] that can be mapped in advance.

 

The Tides

0121083318823_imageeditor_public_domain_moon_face[1].jpg

The moon phase is called lunar phase and refers to the appearance of the illuminated portion of the moon as seen from earth. 

As the brightness of the moon increases, it is said to “wax,” and to “wane” as it decreases

Contrary to what we often understand, lunar phases[4] are not caused by shadows of the earth on the moon (such as that occurring during a lunar eclipse[5]); but rather the result of looking at the illuminated half of the moon from different viewing geometries.  The moon exhibits different phases as the relative geometry of the sun, earth, and moon alter: appearing as a full moon when the sun and moon are on opposite sides of the earth, and as a new moon[6] when they are on the same side.

The phases of full moon and new moon are known as “syzygies,” occurring when the earth, moon, and sun rest (generally) in a straight line.

 
 
moonphases-4.png
 

Even though it takes the moon 27.3 days to go around the earth once (the sidereal month: the time it takes the moon to make one orbit about the earth related to the fixed stars), by the time it gets back to its original position, the position of the sun has changed; slightly altering the visible phase of the moon.  Because of this, a lunar month (lunation,[7] the time between two full moons; and between successive occurrences of the same phase) takes slightly longer: 29.53 days (the synodic month: 29 days, 12 hours, 44 minutes).

 
 
 
 Vintage astrology/lunar map

Vintage astrology/lunar map

As such, the timing of the moon's phases shifts by an average of about one day for each successive month; but the general concept is known as a “monthly” timeframe.

The difference is caused by the fact that the earth-moon coordination is orbiting about the sun at the same time the moon is orbiting about the earth.  

The actual time between two syzygies is variable because the orbit of the moon is elliptic and subject to various periodic perturbations (deviation from a regular orbit around its primary), which change the velocity of the moon.  Also affecting the moon’s visible appearance and gravitational pull is the earth’s “wobble,”" (the angle of the earth’s tilt on its axis —like a spinning top— or obliquity, varies with regard to the plane of the earth’s orbit), involving the fluid nature of the earth’s core, and recently discovered to be influenced by fluctuating pressure on the bottom of the ocean, caused by wind driven changes which alter temperature
and salinity.[7]

 A vintage lunar map

A vintage lunar map

 

“Spring tides” and the Public Trust area

 Aligned gravitational forces...

Aligned gravitational forces...

 


Tides in Fairfield are generally semidiurnal, with two high waters and two low waters each day, (but in some locations can be diurnal, or one tidal cycle per day)[8].  The moment that the tidal current ceases, is called slack water or slack tide (most readily observed at the boat basin adjacent to Jennings Beach, where it is often nearest to high water and low water); it then reverses direction and is said to be turning.  Since the sun and moon both are producing tides, they work both with and against each other, which affects the amount of public trust area we can expect in Fairfield.  As we’ve learned, under the new moon and full moon phases, the lunar tides line up with the solar tides (the sun, moon and earth line up in "syzgy"), so that the tidal forces of the sun reinforce those of the moon (the “bulge” is increased). Under these conditions, the tidal range is then maximized by about 20%, called spring tides, (“spring” used in the context: “to jump” or “to leap up”) creating high tides that are extra high and low tides that are lower.

Spring tides can yield hundreds of extra lateral feet of Public Trust area to walk with your dog off-leash: as noted on our Tide Calendar, spring tides occur on the 16th and (March) 1st of this month.

"Neap Tides" and the Public Trust Area

Likewise, under first and last quarter moon, the solar high tide is located at the lunar low tide (the sun and moon are separated by 90° when viewed from the earth); and the solar low tide is at the lunar high tide.  The lunar tides are larger than the solar tides, and so dominate, but are moderated (since the forces induced by the sun
partially cancel those of the moon). 

At these stages of the lunation, the tide's range is at its minimum (smaller than normal tides), referred to as “neap tides” (and perhaps, for our purposes, are not quite as much appreciated!);
and are also generally twice a month.

 
 

"Perigee" and "Apogee"

 The relationships that affect gravitational pull and the tides.

The relationships that affect gravitational pull and the tides.

Other phenomena influence the tidal range: most particularly, that the moon and earth do not have circular orbits, but slightly elliptical trajectories.  This means that at certain times the moon is closer to the earth than other times: referred to as perigee, the effect of the moon's gravity on the tides is most stalwart.  In like way, when the moon is farthest (apogee), its effect is consequently weakened. 

Concurrently, the earth's orbit is also elliptical: when it is closest to the sun (perihelion, occurring in early January), the solar tides are bigger than normal; and when farthest from the sun (aphelion, in early July) the solar tides are correspondingly weaker than normal.[9]

 Competing gravitational forces...

Competing gravitational forces...

 

Endnotes


 Billie: the gaze of a courser...

Billie: the gaze of a courser...

[1]  Bathymetry refers to the study of underwater depth of the 3rd dimension of ocean floors; data used to make bathymetric maps is acquired through echosounder (sonar) apparatus.

[2]  Among the reasons why, on some days (approximately every two weeks), there is only one low tide in a given day.

[3]  There is also a yearly pattern: An equinox occurs twice a year (March 21st and September 21st), when the tilt of the earth's axis is neutral (inclined neither away from nor towards) the sun, which is directly above the equator.  At this time the spring tides (see, discussion above) are extreme: the highs are exceptionally high and the lows are exceptionally low. 

In parallel, twice a year (June 21st and December 21st) the tilt of the earth's axis is most inclined toward or away from the sun: causing the sun's apparent position in the sky to reach its northernmost or southernmost soverign. This is referred to as solstice, (derived from the latin sol- [sun] and sistere [stand still]; since at the solstices, the sun stands still in declination, wherein the ostensible movement of the sun's path north or south comes to a stop before reversing direction.  As such, augmentation of the tides should be understood as influenced by the proximity of the earth, moon and sun to each other; but also affected by the angle of the moon's orbit about the earth.

[4] As the brightness (lighted portion) of the moon increases, it is said to “wax,” hence: waxing crescent→ first quarter→ waxing gibbous→ full moon; and as the visible face of the moon begins to decrease, it “wanes,” thereby: waning gibbous → third quarter→ waning crescent→ new moon (not visible).

5] It might be expected that once every month when the moon passes between earth and the sun during a new moon, its shadow would fall on earth causing a solar eclipse; (likewise, during every full moon, we might anticipate a lunar eclipse as the earth's shadow falls on the moon). Neither happens, because the plane of the moon's orbit around the earth is tilted by about 5 degrees with respect to the plane of earth's orbit around the sun.  Whether full or new, the moon is positioned near enough to the intersection of earth's orbit plane about the sun and the moon's orbit plane about the earth (called nodes) only twice a year: so there are between 2 and 5 eclipses in a calendar year, mostly partial; a true eclipse (in a given location) being rare.

[6] The new moon may be referred to as dark moon, (not visible at night).  Originally this term referred to the crescent on the first night it is visible: 19th century maritime records distinguish the dark moon (no moon) from the new moon (young crescent).  

vintage_astrology_plate-png.png

[7]  The Earth is not a perfect sphere but an oblate spheroid; that is, it bulges at the equator, and as such, the pulls of the sun and moon cause it to slowly wobble.  As it rotates on its axis, it precesses like a wobbly spinning top, but it also nutates, or wobbles along the circular precession path.  Thus, axial precession is a gravity-induced, slow, and continuous change in the orientation of an astronomical body's rotational axis.  It was first explained by Sir Isaac Newton.  The position of the Earth in its orbit around the sun at the solstices, equinoxes, or other time defined relative to the seasons, thereby slowly changes.*

 The earth rotates with a wobble, like a spinning top, known as "axial precession"

The earth rotates with a wobble, like a spinning top, known as "axial precession"

[8]  Because of the diurnal augmentation (that is: when there is only one cycle of tide in the 24.84 hours in a “tidal day”), there is a difference in height (the daily inequality) between the two high waters on a given day: tide tables differentiate the these as the higher high water and the lower high water; (likewise, the two low waters are referred to as the higher low water and the lower low water). The daily inequality changes over the two-week cycle, and is generally lessened when the moon is over the equator.  See: “What is a Tidal Datum” on this site.

 

[9]  Lunation number: lunation is the period of a synodic revolution of the moon, or the time from one new moon to the next, which varies in length at different times from about 29¼ to 29-5/6 days.  The average length is 29 days, 12 hours, 44 minutes, and 2.9 seconds; (lunation numbers are noted on our Low Tide Calendar: download above).

[10] Every 7½ lunations (about three times a year), lunar perigee (the moon is closest to the earth within its eliptical orbit) coincides with either a new or full moon, and produces the perigean spring tide (the moon is closest to the Earth during the spring tide) with the largest tidal range.  If a storm moves onshore at this time the consequences can be especially dramatic.

*It takes about 26,000 years for Earth’s axis to complete one circle of precession. As a result of this motion, the point where our axis points in the sky changes as time goes on.  While Polaris is the star closest to the north celestial pole today (it will reach its closest point around the year 2100), about 5,000 years ago it was close to a star called Thuban.  In 14,000 years the star Vega in the constellation of Lyra will be the North Star.

 
 
 Harley: surfside sportsman...

Harley: surfside sportsman...

 
 
Pumpernickle was a total surprise. I didn’t expect to be changed constitutionally by a dog. But it quickly became apparent that the description of “a dog” didn’t capture the astounding abundance of facets to her, the depth of her experience, and the possibilities of a lifetime of knowing her... (continued)
— Alexadra Horowitz: Inside of a Dog; What Dogs See, Smell, and Know
 
 
 James: staging an (affectionate) attack!

James: staging an (affectionate) attack!

 

Before long, I felt pleasure simply at her company and pride at watching her act. 
She was spirited, patient, willful, and disarming all in one great furry bundle.

Every dog owner would agree with me, I suspect, about the specialness of his own dog.  Reason argues that everyone must be wrong:
by definition, not every dog can be the special dog—else special becomes ordinary. 
But it is reason that is wrong: what is special is the life story that each dog owner creates with and knows about his own dog.

When Pump was nearly at the end of her life,
undeniably old, she lost weight, her muzzle grayed, she slowed sometimes to a stop on walks.
I saw her frustrations, her resignations, her impulses pursued or abandoned;
I saw her considerations, her control, her calm. 

But when I looked at her face, and into her eyes, she was a puppy again.

I saw glimpses of that unnamed dog who so cooperatively let us plop a too-big collar around her neck
and walk her out of the shelter and thirty blocks home. 
And then thousands of miles since.”
—Alexadra Horowitz: Inside of a Dog; What Dogs See, Smell, and Know

 
 ICHA: Snow (woman)

ICHA: Snow (woman)