There are many different Lunar Cycles. I think they are involved in how the weather cycles over various time frames. So I’m just going to be ‘taking some notes’ here, so that I don’t have to keep running all over the place when I want to see if some other thing matches one of these lunar cycles.
The first, and most basic, is just that the Moon orbits the Earth so we have phases of the moon. Though even that isn’t quite as simple as it sounds. “Why?” is interesting. See, the Moon never goes “retrograde”. It’s always moving forward, but just goes slower on one side than on the other. The Earth and Moon are in a ‘one way dance’ speeding up and slowing down, but always moving forward. That, btw, is also part of why I think we are really a “two planet system” rather than a planet and moon.
So while we are used to thinking of the Moon as doing laps around the Earth, the reality is more that we co-orbit the Sun and do a little ‘speed up / slow down’ dance relative to each other and with some ‘inward – outward’ and ‘up – down’ wiggles. This has interesting implications very long term as we ‘lose the Moon’ and it’s orbit “around” us gets larger. What happens when it is swinging each side of OUR solar orbit in larger loops, but not centered on us? It’s not like it will be escaping from this particular Solar orbit fast. Hopefully we go into some kind of resonance orbit so we don’t try to be in the ‘same place and time’… But that’s billions of years away and who knows what might mess things up before then. Like the sun surface coming out to about this orbit as the sun ages.
For now, just remember that it’s more of a ‘co orbit’ than a ‘circles us’, even though we’ll be talking about things as though it really does just do laps around us.
Some notes from the wiki:
They use “orbit of the moon” and reserve “lunar orbit” for the path taken by spacecraft to get to the moon. I’m going to use both to mean “orbit of the moon” as I don’t see anyone being confused about that ‘issue’ here.
The Moon completes its orbit around the Earth in approximately 29.5 days (a synodic month). The Earth and Moon orbit about their barycentre (common centre of mass), which lies about 4600 km from Earth’s centre (about three quarters of the Earth’s radius). On average, the Moon is at a distance of about 385000 km from the centre of the Earth, which corresponds to about 60 Earth radii. With a mean orbital velocity of 1,023 m/s, the Moon moves relative to the stars each hour by an amount roughly equal to its angular diameter, or by about 0.5°. The Moon differs from most satellites of other planets in that its orbit is close to the plane of the ecliptic, and not to the Earth’s equatorial plane. The lunar orbit plane is inclined to the ecliptic by about 5.1°, whereas the Moon’s spin axis is inclined by only 1.5°.
Why is the lunar orbit close to the plane of the ecliptic and not the Earth equatorial plane? Remember that “twin planets both orbiting the Sun” point above?…. Planets orbit in the ecliptic, or very close to it. Think about that for a minute.
Yes, it’s a slightly different plane. The invariable plane.
Most of the bodies of the Solar System orbit the Sun in nearly the same plane. This is likely due to the way in which the Solar System formed from a protoplanetary disk. Probably the closest current representation of the disk is known as the invariable plane of the Solar System. The Earth’s orbit, and hence, the ecliptic, is inclined a little more than 1° to the invariable plane, and the other major planets are also within about 6° of it. Because of this, most Solar System bodies appear very close to the ecliptic in the sky.
We have a ‘synodic month’ that is one circle of the moon around the earth relative to the sun. It gives us the phases of the moon. So from one full moon to the next (or one new moon to the next). As the Earth is moving relative to the Sun also, there are several other kinds of month as well.
Month type Length in days anomalistic 27.554549878 − 0.000000010390 × Y sidereal 27.321661547 + 0.000000001857 × Y tropical 27.321582241 + 0.000000001506 × Y draconic 27.212220817 + 0.000000003833 × Y synodic 29.530588853 + 0.000000002162 × Y
These all wander a little bit in actual length. Giving the measurement to so many digits of precision is a bit silly, really, given that “things move” up there. Notice that the first 4 are all almost the same.
Sidereal month is measured against the fixed stars. This is in some ways the most basic and consistent month.
Tropical month is measured against the Equinox. This month includes precession artifacts ( or perhaps that orbit of a paired star that we call precession having not found the star yet…)
The Draconic month measures against the ‘node’ where the orbit of the moon swaps from above to below the ecliptic. The lunar orbit is slightly inclined (about 5 degrees). We can only have eclipses when it is on one of those ‘nodes’ and thus is in line with the Sun – Earth line. The precession of the orbit changes where those ‘nodes’ are around the Earth, and when they line up, we get an eclipse. That cycle is about 18.6 years (sometimes I’ll talk about a ’19 year lunar cycle’, that’s this one.)
Because the moon’s orbit is inclined with respect to the ecliptic, the sun, moon, and earth are in line only when the moon is at one of the nodes. Whenever this happens a solar or lunar eclipse is possible. The name “draconic” refers to a mythical dragon, said to live in the nodes and eat the sun or moon during an eclipse.
So the difference between the sidereal, tropical, and draconic months all come down to very long cycle things having an effect, or not. The synodic is changed by a very fast moving thing, the Earth, racing around the Sun, and how long it takes the Moon to get far enough ahead on that orbit, again, to line up with the Sun.
So that leaves “anomalistic” month. I’m just going to quote the wiki here as it’s a bit complex.
The Moon’s orbit approximates an ellipse rather than a circle. However, the orientation (as well as the shape) of this orbit is not fixed. In particular, the position of the extreme points (the line of the apsides: perigee and apogee), makes a full circle (lunar precession) in about nine years. It takes the Moon longer to return to the same apsis because it moved ahead during one revolution. This longer period is called the anomalistic month, and has an average length of 27.554551 days (27 d 13 h 18 min 33.2 s). The apparent diameter of the Moon varies with this period, and therefore this type has some relevance for the prediction of eclipses (see Saros), whose extent, duration, and appearance (whether total or annular) depend on the exact apparent diameter of the Moon. The apparent diameter of the full moon varies with the full moon cycle which is the beat period of the synodic and anomalistic month, and also the period after which the apsides point to the Sun again.
So basically it is measured relative to the end of the “loop” rather than relative to the crossing of the zero line (ecliptic). As this precesses, it takes more time to get back to that extreme end in the new position. We also start to see where some of the other odd cycles come from. Beat frequencies. So the beat frequency between this anomalistic month and the synodic phase of the moon month gives use the varying sizes of the full moon.
A Druid on the ground with a Henge will be observing these various cyclical changes and trying to figure out how to predict them, and what they mean. A Sailor trying to predict the tides will be dealing with these beat frequency effects, too, as they add up to the total pull of the Sun and Moon on the seas. Not all ‘full moon tides’ will be the same size, even though the sun and moon are in a straight line.
That’s the basics. The various changes of orbit interacting, each with their own period, make a bunch of other cycles and beat frequencies that actually change things on earth. From tides to darkness of night to eclipses and, IMHO, weather cycles as well.
Sidebar on Henges and Agriculture
I think that is only a part of what the Druids were doing with their Henges. Figuring out these cycles, exactly, and how to predict everything from eclipses to longer term weather cycles. Being able to say “we will now have a bad rain year” would be of great advantage. We see the same thing in the Maya writings. They predicted what years would be good years, and bad years, for crops and weather.
There are a whole lot of other interesting things about various months on that link, and several are religious calendar oriented. It is one of the few universal things seen across cultures, centuries, millenia, continents, etc. Folks make calendars, often based on the moon, and have dedicated, honored, folks who’s duty is to keep it right. This has clearly been a ‘big deal’ for ancient societies. Is it just superstition that the phase of the moon affects plant growth and germination? Well, no.
During both the full and new moons there is higher moisture content in the soil. The seeds absorb the higher water content, which causes germination to occur more rapidly.
At Northwestern University, Dr. Frank Brown conducted a 10-year study showing that during a full moon, plants absorb more water. The study was conducted in a laboratory setting, and even though the plants were out of sight of the moon, its gravitational pull still influenced the plant’s absorptive qualities.
Further studies regarding the effects of the moon’s phases on plant germination involved root crops–one conducted by Lili Kolisko in 1939 and another by Maria Thun in 1956. Both showed that root crops achieved maximum germination in the days just prior to a full moon
Yes, tides in the ground water. Think that might “lubricate” some fault lines too? Just sayin’…
Now some folks do make it sound a bit like “magical thinking”, except that plants have been evolving to eek out any advantage they can over their neighbors and knowing when to concentrate on roots vs leaves can be easily done with hormones that have a gravity gradient that moves ‘with the tides’, so maybe it’s not so “magical”.
John Jeavons, author of “How to grow more vegetables…” adds the influence of the increasing or decreasing moonlight on the growth of plants. When the moon is in it’s waxing phases the ” increasing amount of moonlight stimulates leaf growth”, and ” as the moonlight decreases the above ground leaf growth slows down. The root is stimulated again.” (3)
Further tests have been conducted, most notably by Frau Dr. Kolisko in Germany in 1939, and by Maria Thun in 1956. They primarily experimented with root crops, showing the effect of lunar phases on seed germination. They found maximum germination on the days before the Full moon. Crop yields were reported by weight.
Thun was surprised to discover that the signs of the zodiac played its’ part as well. Thun experimented with a variety of crops: carrots and parsnips represented root crops; lettuce, spinach and corn salad as leaf types; beans, peas, cucumbers and tomatoes as fruit seed types; zinnias, snapdragons and asters were air crops. Crops responded well when planted in the appropriate sign for their type of plant. There were some exceptions, however. Some plants seemed to favor signs other than what would appear to be logical; for instance the brassica family, (broccoli, cauliflower, etc.) which one might consider flowering types, seemed to favor water signs. Cucumbers sown on leaf days had strong leafy growth, but did not produce many flowers. Their tests also seemed to indicate that responses to lunar planting were heightened when planted in organic soil that had not been treated with chemical fertilizer or pesticides.
Ute York, in her book “Living by the Moon” says
“The old-time gardeners say, “With the waxing of the moon, the earth exhales. ” When the sap in the plants rise, the force first goes into the growth above ground. Thus, you should do all activities with plants that bear fruit above ground during a waxing moon. With the waning of the moon, the earth inhales. Then, the sap primarily goes down toward the roots. Thus, the waning moon is a good time for pruning, multiplying, fertilizing, watering, harvesting, and controlling parasites and weeds”
Plants sown in the correct combination of the best lunar phase and sign show increased vigor, due to having all the best influences. They are growing at an optimum rate and are not as prone to setbacks that would affect less healthy plants. Harvests are often quicker, larger and crops don’t go to seed as fast.
How much of that is the result of generations of observation and how much is just a crock? I have no idea. But it looks pretty easy to test, and at least some of it has been tested and found to have an effect. (Though picking out which parts might take a while).
My Father once shared with me the ‘folk wisdom’ of when to plant potatoes. It was dated off of a full moon after a particular holiday. That would be a solar calendar and a lunar phase. Sadly, I didn’t bother to remember the specifics as it was “unscientific”… But we can say that exactly that kind of ‘planting calendar’ was used historically by farmers. Generally speaking, farmers are not prone to doing too many silly things, and especially not if it actually hurts productivity.
So all in all, I think that means that folks 5000 years ago were likely aware of solar and lunar calendars, and were looking at longer cycles too. Among the ‘holes’ at StoneHenge are a set of 19 that look ideal for counting a longer cycle of the Moon. The Aubry Holes around the outside, with a sun and moon stone counter in them, make a decent eclipse predictor / tracker. Taken together, they let you find the equinox, track the cycles of the moon, predict eclipses, and even compare siderial, tropical, draconic, synodic and likely even anomalistic months. The “why” would be if those are useful for long term planning. I think they clearly do have benefit / advantage.
For astronomy and calendar studies, the Metonic cycle or Enneadecaeteris (from Ancient Greek: εννεαδεκαετηρις, “nineteen years”) is a period of very close to 19 years which is remarkable for being nearly a common multiple of the solar year and the synodic (lunar) month. The Greek astronomer Meton of Athens (fifth century BC) observed that a period of 19 years is almost exactly equal to 235 synodic months, and rounded to full days counts 6940 days. The difference between the two periods (of 19 years and 235 synodic months) is only a few hours, depending on the definition of the year.
Considering a year to be 1⁄19 of this 6940-day cycle gives a year length of 365 + 1⁄4 + 1⁄76 days (the unrounded cycle is much more accurate), which is slightly more than 12 synodic months. To keep a 12-month lunar year in pace with the solar year, an intercalary 13th month would have to be added on seven occasions during the nineteen-year period (235 = 19 × 12 + 7). Meton introduced the cycle in circa 432 BC, but it was actually known earlier by Babylonian astronomers.
Mechanical computation of the cycle is built into the Antikythera mechanism.
The cycle was used in the Babylonian calendar, ancient Chinese calendar systems (the ‘Rule Cycle’ 章), the medieval computus (i.e. the calculation of the date of Easter) and still regulates the 19-year cycle of intercalary months of the Hebrew calendar.
This is the basic 19 year lunar cycle found all over the globe and found in ancient artifacts. Stonehenge has a 19 hole counter that IMHO was used to keep track of the Metonic Cycle.
This is similar to the Metonic cycle, yet not the same. The Metonic cycle compares phase of the moon to years (position of moon and earth relative to the sun) and finds a repeating interval of almost exactly 19 years. This cycle pays attention to the alignment of the sun, moon, and earth at the time of crossing the ecliptic ( when an eclipse an happen).
Fortunately for early astronomers lunar and solar eclipses repeat every 18 years 11 days and 8 hours in a “Saros” cycle. The earliest eclipse record is over 4000 years old: for failing to predict the solar eclipse of Oct. 22, 2134 BC, the Chinese emperor, caught unprepared, ordered his royal astronomers beheaded. Early eclipse reports from Babylon in 1375 BC, China in 1063 BC and Assyria in 763 BC (in the Bible: Amos 8:9), along with Herodotus’ report that Thales of Miletus predicted the solar eclipse of 585 BC ending a five-year war between the Medes and Lydians, suggest the Babylonians knew of the Saros cycle by the 5th or 4th century BC (see tablet below).
I would assert that Stonehenge shows that the Saros Cycle was being ‘researched’ about 3000 BC. The device is capable of it, and the method has been worked out. The 19 lunar holes let you track, over the years, the stage of the orbit; while the Aubry Holes let you model the sun / moon / earth interaction. The inner 19 holes let you track the Metonic cycle while the Aubry Ring lets you track eclipses, so models the Saros Cycle indirectly.
The saros] is a period of 223 synodic months (approximately 6585.3213 days, or nearly 18 years 11 days), that can be used to predict eclipses of the Sun and Moon. One saros after an eclipse, the Sun, Earth, and Moon return to approximately the same relative geometry, and a nearly identical eclipse will occur, in what is referred to as an eclipse cycle. A sar is one half of a saros.
A series of eclipses that are separated by one saros is called a saros series.
So one simple method of tracking a Saros Cycle would just be to count 223 Synodic Months. Several ancient calendars are based on Synodic Months. To get the exact eclipse dates takes a bit more work, though.
The earliest discovered historical record of the saros is by the Chaldeans (ancient Babylonian astronomers) in the last several centuries BC. It was later known to Hipparchus, Pliny and Ptolemy, but under different names. The Sumerian/Babylonian word “šár” was one of the ancient Mesopotamian units of measurement and as a number appears to have had a value of 3600. The name “saros” (Greek: σάρος) was first given to the eclipse cycle by Edmond Halley in 1691, who took it from the Suda, a Byzantine lexicon of the 11th century. The information in the Suda in turn was derived directly or otherwise from the Chronicle of Eusebius of Caesarea, which quoted Berossus. Although Halley’s naming error was pointed out by Guillaume Le Gentil in 1756, the name continues to be used.
Mechanical calculation of the cycle is built into the Antikythera mechanism.
I’d just add to that: the ancient builders of Henges.
But clearly “folks new” and for a very long time. This mattered to them. I think it very unlikely to have been only due to superstition. I’d point out, for example, that the PDO cycle looks to be about 3 x Saros. The “Polar See-Saw” may also be a related cycle. Remember that the eclipse is just an indication of the cycle, it is also shifting the global tides, and through that, the oceans and weather. Lunar on the ascending vs descending will shift the north vs south pull on water and where the water “piles up” more. North or south of the equator.
The saros, a period of 6585.322 days (14 normal years + 4 leap years + 11.322 days, or 13 normal years + 5 leap years + 10.322 days), is useful for predicting the times at which nearly identical eclipses will occur, and derives from three periodicities of the lunar orbit: the synodic month, the draconic month, and the anomalistic month.
Position relative to the sun, the state of the precession vs ecliptic, and the position of the end of the orbit in space. In other words, exactly where the moon is in it’s orbital pattern. But wait, there’s more…
A complication with the saros is that its period is not an integer number of days, but contains a multiple of ⅓ of a day. Thus, as a result of the Earth’s rotation, for each successive saros, an eclipse will occur about 8 hours later in the day. In the case of an eclipse of the Sun, this means that the region of visibility will shift westward by 120°, or one third of the way around the globe, and the two eclipses will thus not be visible from the same place on Earth. In the case of an eclipse of the Moon, the next eclipse might still be visible from the same location as long as the Moon is above the horizon. However, if one waits three saroses, the local time of day of an eclipse will be nearly the same. This period of three saroses (54 years 1 month, or almost 19756 full days), is known as a triple saros or exeligmos (Greek: “turn of the wheel”).
So the exact spot over the surface of the earth for that peak effect (both the eclipse and the associated tidal forces) changes on a 54 year cycle. Gee, that’s looking rather close to that “nearly 60 year” slow part of the PDO cycle… Anything else that’s at some subharmonic or direct 18 year (ish) period?
Some Weather Talk & Longer Saros Series
Fig 4B. (above right) The two leading eigenfunctions (EOFs) of reconstructed PDO form an oscillatory pair (thick line: first EFO) that accounts for 28.5% of variance. The combined amplitude of those two components has a ~23 year period, and represents the time-varying strength of the bidecadal oscillation.
Fig 4C. (below) Evolutive spectrum of reconstructed PDO, showing a prominent bidecadal mode whose strength was less intense from the late 1700s to the mid-1800s. Lower frequencies (from multidecadal to centennial and longer) in the PDO time series are restricted to the twentieth century
Yeah, 18 isn’t the same as 23, but it’s suspiciously close. The actual PDO changes are somewhat stochastic jerks back and forth, so I’d not be surprised to find many other drivers interacting and causing various lags and beats. But a “bidecadal mode” sure looks like something that could be lunar tidal influenced.
Depending on who looks at what proxy for the PDO, some folks find a 60 year cycle, and other folks don’t. I’m not so much interested in the PDO per se as in the 60 year (ish) cycle of weather. It would be even more interesting if folks tried looking for a 54 year period instead of 60 (and that might even explain some of the lack of finding for some proxies).
The coefficient of determination (R²) for this regression is 88 percent. This means that 88 percent of the variation in average global temperature is explained by a long term trend of 0.5°C per century and a cycle which consists of an approximately thirty-year upswings and downswings.
A 30 (ish) year cycle implies that an 18 year stimulus has to be interacting with something else to create a harmonic result. I’d guess that would be some natural frequency of motion of water in or between the various oceans. It would be interesting to find out if long duration tide charts show a 30 year period in any locations, and / or a 18-19 year period in other.
But even that does not capture the longer cycle effects from the Saros Cycle. Each Saros Cycle runs on a slightly different alignment with the earth. Saros Cycles come in a series.
The saros is based on the recognition that 223 synodic months approximately equal to 242 draconic months and 239 anomalistic months. However, as this relationship is not perfect, the geometry of two eclipses separated by one saros will differ slightly. In particular, the place where the Sun and Moon come in conjunction shifts westward by about 0.5° with respect to the Moon’s nodes every saros, and this gives rise to a series of eclipses, called a saros series, that slowly change in appearance.
And with those moving eclipses there is also a movement of where the maximum tidal forces are applied.
Each saros series starts with a partial eclipse (Sun first enters the end of the node), and each successive saros the path of the Moon is shifted either northward (when near the descending node) or southward (when near the ascending node). At some point, eclipses are no longer possible and the series terminates (Sun leaves the beginning of the node). Arbitrary dates were established by compilers of eclipse statistics. These extreme dates are 2000 BCE and 3000 CE. Saros series, of course, went on before and will continue after these dates. Since the first eclipse of 2000 BCE was not the first in its saros, it is necessary to extend the saros series numbers backwards beyond 0 to negative numbers to accommodate eclipses occurring in the years following 2000 BCE. The saros -13 is the first saros to appear in these data. For solar eclipses the statistics for the complete saros series within the era between 2000 BCE and 3000 CE are given in this article’s references. It takes between 1226 and 1550 years for the members of a saros series to traverse the Earth’s surface from north to south (or vice-versa). These extremes allow from 69 to 87 eclipses in each series (most series have 71 or 72 eclipses). From 39 to 59 (mostly about 43) eclipses in a given series will be central (that is, total, annular, or hybrid annular-total). At any given time, approximately 40 different saros series will be in progress.
Gee… where have I seen a 1500 ish year cycle before… Can you say “Bond Event”? Could there be a mode where, for just a little while in geologic time, the shift of tidal forces cause the Gulf Stream to dramatically slow while things ‘readjust’? Yes, it’s speculative, but say you spent 800 years getting the water moved into the Arctic / Atlantic and then the moon starts pulling it all back into the Pacific? It will take some time to equalize the global oceans and during that time I could easily see less pressure to push the Gulf Stream all the way up north. Yes, just a random speculation. Yet “water moves”… so something must happen.
When oscillating tidal currents in the stratified ocean flow over uneven bottom topography, they generate internal waves with tidal frequencies. Such waves are called internal tides.
Shallow areas in otherwise open water can experience rotary tidal currents, flowing in directions that continually change and thus the flow direction (not the flow) completes a full rotation in 12½ hours (for example, the Nantucket Shoals.
Clearly tidal forces can change what happens in the oceans away from land and ought to be able to influence the Gulf Stream and related types of currents. The Gulf, in particular, has a bottom topology that would lend itself to modification of water flows.
Also, in some places at least, longer term tide changes have been correlated with lunar cycles.
9 Year Cycle
Whether large bores occur after new moons or full moons varies due to the fact that there is a nine-year cycle. The cycle runs as follows:
– highest tides occur following a new moon
– the highest tides at new and full moons are approximately equal
– highest tides occur following a full moon
– the highest tides at new and full moons are approximately equal
There’s a lot in this link, but I’m going to focus just on the tide anaysis:
A 2012 paper (Chambers et al, “Is there a 60-year oscillation in global mean sea level?”, Geophysical Research Letters Vol 39 [ http://www.agu.org/pubs/crossref/2012/2012GL052885.shtml ] ) states: “We examine long tide gauge records in every ocean basin to examine whether a quasi 60-year oscillation observed in global mean sea level (GMSL) reconstructions reflects a true global oscillation, or an artifact associated with a small number of gauges. We find that there is a significant oscillation with a period around 60-years in the majority of the tide gauges examined during the 20th Century, and that it appears in every ocean basin. Averaging of tide gauges over regions shows that the phase and amplitude of the fluctuations are similar in the North Atlantic, western North Pacific, and Indian Oceans, while the signal is shifted by 10 years in the western South Pacific. The only sampled region with no apparent 60-year fluctuation is the Central/Eastern North Pacific. The phase of the 60-year oscillation found in the tide gauge records is such that sea level in the North Atlantic, western North Pacific, Indian Ocean, and western South Pacific has been increasing since 1985–1990. Although the tide gauge data are still too limited, both in time and space, to determine conclusively that there is a 60-year oscillation in GMSL, the possibility should be considered when attempting to interpret the acceleration in the rate of global and regional mean sea level rise.”
The following figure from that paper shows the approximately 60-year cycle in the sea level data.
So, in my opinion, there is ample evidence for a lunar tidal cycle of at least 18 years (and half that of 9 years) along with a longer term ‘near 60′ year cycle. That, then, would argue that the same physics ought to cause the 1500 (ish) year lunar tidal changes to also be reflected in ocean tide cycles. It is my opinion that moving that much water around the planet, and changing the depths and mixing of the ocean, will also cause changes in the temperature profile of the waters and the resultant weather.
1800 year, 5000 year, even 23,000 year tidal cycles
Claims to find just such a tidal pattern ( though at the period of 1800 years):
The 1,800-year oceanic tidal cycle: A possible cause of rapid climate change
Charles D. Keeling* and Timothy P. Whorf
Variations in solar irradiance are widely believed to explain climatic change on 20,000- to 100,000-year time-scales in accordance with the Milankovitch theory of the ice ages, but there is no conclusive evidence that variable irradiance can be the cause of abrupt fluctuations in climate on time-scales as short as 1,000 years. We propose that such abrupt millennial changes, seen in ice and sedimentary core records, were produced in part by well characterized, almost periodic variations in the strength of the global oceanic tide-raising forces caused by resonances in the periodic motions of the earth and moon. A well defined 1,800-year tidal cycle is associated with gradually shifting lunar declination from one episode of maximum tidal forcing on the centennial time-scale to the next. An amplitude modulation of this cycle occurs with an average period of about 5,000 years, associated with gradually shifting separation-intervals between perihelion and syzygy at maxima of the 1,800-year cycle. We propose that strong tidal forcing causes cooling at the sea surface by increasing vertical mixing in the oceans. On the millennial time-scale, this tidal hypothesis is supported by findings, from sedimentary records of ice-rafting debris, that ocean waters cooled close to the times predicted for strong tidal forcing.
High resolution ice-core and deep-sea sediment-core records over the past million years show evidence of abrupt changes in climate superimposed on slow alternations of ice-ages and interglacial warm periods. In general these abrupt changes are spaced irregularly, but a distinct subset of recurring cold periods, on the millennial time-scale, appears to be almost periodic. Such events, however, are not clearly apparent in ice-core data after the termination of the most recent glaciation, about eleven thousand years (11 kyr) BP (kyr before A.D. 2000). This absence of recent events has led to the hypothesis that their underlying cause is related to internal ice-sheet dynamics (ref. 1, p. 35). Interpretations of sediment-cores by Bond et al. (1, 2) indicate, however, that a 1- to 2-kyr periodicity persisted almost to the present, characterized by distinct cooling events, including the Little Ice Age that climaxed near A.D. 1600. Although evidence that cooling was more intense during glacial times may be explained by some aspect of ice-dynamics, a continuation of cooling events throughout the postglacial Holocene era suggests an alternative underlying mechanism.
The paper goes on from there and is well worth the read. The key “take away” from this abstract is just that there are tidal mechanisms that have periods of 1800 and 5000 years. Very close to specific patterns seen in the weather / climate data. The Bond Cycle has been characterized as 1470 or 1500 years, but when the data are carefully inspected it appears to be bi-modal with that 1500 years being the average of two modes, one of which is 1800 years.
Then there is the “how”. Mixing cold water to the surface. As we saw a ‘tongue of blue cold’ shoot out into the Pacific just a couple of years back on the shift of the PDO, that sure looks plausible to me. Add in that the whole ocean is going cold right now and it fits.
We propose that variations in the strength of oceanic tides cause periodic cooling of surface ocean water by modulating the intensity of vertical mixing that brings to the surface colder water from below. The tides provide more than half of the total power for vertical mixing, 3.5 terawatts (4), compared with about 2.0 terawatts from wind drag (3), making this hypothesis plausible. Moreover, the tidal mixing process is strongly nonlinear, so that vertical mixing caused by tidal forcing must vary in intensity interannually even though the annual rate of power generation is constant (3). As a consequence, periodicities in strong forcing, that we will now characterize by identifying the peak forcing events of sequences of strong tides, may so strongly modulate vertical mixing and sea-surface temperature as to explain cyclical cooling even on the millennial time-scale.
So while the winds do cause mixing and can cause ENSO et. al., the tides matter too. Perhaps even more so.
They then go on to talk about how they calculate the tidal energy with various ways of handling long term estimates of synodic and anomalistic et. al. months. Eventually arriving at:
A time-series plot of Wood’s values of γ (Fig. 1) reveals a complex cyclic pattern. On the decadal time-scale the most important periodicity is the Saros cycle, seen as sequences of events, spaced 18.03 years apart. Prominent sequences are made obvious in the plot by connected line-segments that form a series of overlapping arcs. The maxima, labeled A, B, C, D, of the most prominent sequences, all at full moon, are spaced about 180 years apart. The maxima, labeled a, b, c, of the next most prominent sequences, all at new moon, are also spaced about 180 years apart. The two sets of maxima together produce strong tidal forcing at approximately 90-year intervals.
Gee, haven’t we seen a 180 ish year cyclical from time to time? Often attributed to the solar cycle. But as the lunar orbital motions are modulated by the same planetary / orbital resonances as move and modulate the sun, these “come together when they come”. Now we have a mechanism for that “solar driven cycle”. Yes, variations in TSI are too low, but variations in clouds and tides are not. Especially when they work in tandem.
The caption says:
Varying strength in an estimate of the tide raising forces, derived from Wood (ref. 5, Table 16). Each event, shown by a vertical line, gives a measure of the forcing in terms of the angular velocity of the moon, γ, in arc degrees per day, at the time of the event. Arcs connect events of strong 18.03-year tidal sequences. Centennial maxima are labeled, with the final one, “D”, occurring in A.D. 2151.
The peaks on that chart ought to match cold times, and the valleys warm times. In 1710-20 it was relatively warm in Sweden. It then got very cold into the late 1700s and early 1800s. We gradually warmed out of that period, hitting a peak warmth just about the bottom of that dip in the darker bottom bars in 1930s. Cooled into about the mid 1970s, and then warmed to the present, with the hottest being at 1998, just about at that other bottom in the darker bottom lines where it is almost white to the 2000 mark. Now we’re headed back up the next set of rising lines in that bottom dark series.
So as I read that graph, it sure looks like it tracks pretty well with the known history of weather. 1974 wasn’t as cold as 1816, but we didn’t have a major volcano blow off either. It DID snow on the valley floor of the Central Valley in the mid ’70s. The year it snowed was the year I decided to see if I could go bare foot for an entire year… so I strongly remember all the folks talking about how unusual it was to have snow while contemplating the metal pedals on my bike… Glaciers were growing, the New Ice Age was in all the magazines. It was cold.
So looks to me like Lunar Cycles pretty much call the tune (though likely with a solar forcing ‘kicker’ as they do move together when they move). If that is the case, this chart says we get colder for the next 35 years (to the little ‘c’ point) then have a bit of warming. The authors place more emphasis on the peak dates, but I’m looking at a ‘visual weighting’ of the mass of ink at the bottom. I think that the total integrated tide forces are likely to matter more than a given peak event. (Though I think that peak event likely manifests as a particularly bad / cold / snowy year or three…)
The paper goes on to find and illustrate 5000 year and even a 23,000 year tidal force cycle. That could explain some details such as why we had a shorter term cold spell in the 1970s but not a full on Little Ice Age. It would also explain all of the modern warming as being via a confluence of a few of those cycles that gives us the ‘stair steps up’ shape we’ve seen in the data. The 180 year period being relatively flat in the above graph, but in reality laid on top of a 5000 year cycle
Here is a look at the 1800 year cycle over a longer time period (Click for bigger version):
Comparison of late-glacial and Holocene sedimentary core chronology of the North Atlantic Ocean basin with the times of tidal forcing. Tidal events are shown as in Figs. 1 and 2 with times of 1,800-year climactic events (in kyr BP) listed below. These climactic events are connected by line segments. Those that contribute to the 5,000-year tidal cycle are marked with asterisks. Immediately above this plot are vertical lines indicating cool periods inferred from the deep-sea core records, labeled as in Fig. 5. Their timing is derived from Fig. 5, except for Event 1 and Events 3–8, which are dates quoted in the text of ref. 2, and Event 2, inferred from Bond et al. (ref. 1, Fig. 14). Plotted as arrows are the times of dust layers in Elk Lake, Minnesota, the beginning of the Akkadian drought [as reported by Kerr (9)], the Little Ice Age, and the end of the Younger Dryas (YD) [Bond et al. (2)]. Events consistent with the hypothesis of tidal forcing of climate are shown as solid lines, exceptions as dashed lines.
Looks like it’s pretty much “spot on” for major known climate cold disasters. As I’m pretty sure that the Younger Dryas was an impact event into the ice sheet, I’m not bothered that it shows up as a ‘miss’ on tidal driven cycles. Note that this graph is in ‘years before present’, so we are at about the “0” point on the graph (depending on when ‘present’ was when they made it). That’s pretty much the bottom of a warm dip.
It looks to me like, going forward in time past zero, we have about a 1500 year plunge into cold staring us in the face. Worse than the Little Ice Age (higher peak and greater ink density in the middle). The really good bit, though, is that it looks like we’re somewhat warm for a couple of hundred years until it gets really rolling. So “not my problem”…
That’s all just based on lunar tidal effects, though, so we will find out if a Sleepy Sun has a big enough impact to gives us a cold 30 years even if that doesn’t show up on this long duration time scale… It’s hard to read, but that first chart looks like it has a spike that goes up to touch the line ‘c’ at about ‘now’. So perhaps a cold decade then some relief.
We also have to keep in mind that this is in the context of a constantly changing insolation pattern and that we’re ‘on the edge’ of the flip into the next glacial, so at some point that shift in the ocean currents will happen. It is possible that the next “dip” into cold in 1500 years or so will be unrecoverable to our present level of warmth and that we’ll be on our way to glaciation about then.
At this point I think I’ve reached the end of the lunar cycles on various time scales. If I run into any more, I’ll add them. I would only note that the 23,000 year cycle they mention in the paper is remarkably similar to the precession period of the Earth (or the potential orbital period of our Sun about a companion star) and thus is also the Maya calendar cycle. I suspect that what the Maya calendar cycle was saying was not that this is ‘the end’, but rather that this is as good as it gets and the next many thousands start a long slow slide into cold. My read on the 23,000 year cycle chart looks like we’re about at the turn to the other direction. Add that to a 5000 year cycle turn and an 1800 year peak warmth spot, well, lets just say I’d not be moving to Alaska any time soon. Florida and Texas would be better choices.
As those cold spikes also were times of droughts in the north (Minnesota lake sediments) or Egypt / Mesopotamia (Akkadian empire fell, and Egyptians had a great famine then too in the 4.2 ky event IIRC) while in the L.I.A. Europe was soaked in cold rains; expect some ‘re-arranging’ of where the water goes in the next centuries. (At least, I hope it is centuries away… and the Sleepy Sun doesn’t give us a ‘taster’ sooner…)
All in all, it looks like the world of about 3500 AD “has issues”. Then again, I’m hoping we make it that far, and if we do, are already living on other planets and in orbital colonies. We really do need to start getting off this rock. It’s just not all that safe and stable a place…
Until that time, though, it looks to me like the Moon matters as much as the Sun, and that watching both the Moon and Sun can explain pretty much all of the weather cycles that “climate scientists” like to pretend is climate.