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TIDAL CYCLES & CLIMATE CHANGE

Posted on: August 5, 2018

THE HOLOCENE

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RELATED POST ON HOLOCENE TEMPERATURE DYNAMICS [LINK]

 

Schematic chart about the spring-neap tidal variation in a lunar ...

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SYZYGY ALIGNMENT 

Figure 7

Figure 6

 

FIGURE 5: Glacial-Holocene deep-sea core record of ice-rafted debris, petrology, and isotopes of the North Atlantic Ocean basin which shows evidence of pervasive millennial-scale fluctuations in climate. Overlaid in red are times of peak forcing in the 1,800-year tidal cycle.

Figure 5

FIGURE 4: Multitaper spectral analysis of glacial-Holocene petrologic events from cores VM 29–191 and VM 23–81 compared with periodicities in tidal forcing. Overlain in red are the averages of the 1,800- and 5,000-year tidal periods (A) and times of peak forcing of the former cycle (B). Tidal timing and periodicity assume invariant orbital parameters, except for the 5,800-year period that is based on assuming secular variability of climatic precession, as described in the “Secular Variations in Tidal Forcing”

Figure 4

FIGURE 3: Varying strength of the global tide raising forces with parameters that reveal the basis for the 1,800- and 5,000-year tidal cycles, as described in the text. The plots are for a hypothetical 110-kyr sequence of tidal events beginning with the moon, sun, and earth in perfect alignment and closest approach (zero separation-intervals), producing a maximum γ of 17.165° per day never again attained. Tidal events occurring near peaks in the 5,000-year cycle (near zero crossings of top plot) are connected by straight lines to reveal their pattern (which includes a 23-kyr cycle not discussed in the text).Figure 3

FIGURE 2: Millennial periodicity in tide raising forces since 500 B.C. The angular velocity, γ, was computed from functions listed in Table 2. Events of a 180-year cycle, all at full moon, are labeled with times of occurrence (B.C. or A.D.). The 1,800-year cycle is evident as a progression of solar-lunar declination difference, listed at the top of the figure in degrees of arc of the moon above (or below) the ecliptic.Figure 2

FIGURE 1: Varying strength in tide raising forces. 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.Figure 1

 

 

 

TIDAL CYCLES AND GLOBAL WARMING

  1. THE TIDAL CYCLE THEORY OF CLIMATE CHANGE EXPLAINS THE 12,000 YEAR HISTORY OF MILLENNIAL SCALE WARMING AND COOLING CYCLES SEEN IN THE HOLOCENE [LINK] . IN CONTRAST, THE CLIMATE SCIENCE AGW CLIMATE CHANGE THEORY EXPLAINS THE POST LIA WARMING BUT HAS NO EXPLANATION FOR THE OTHER WARMING AND COOLING CYCLES OF THE HOLOCENE [LINK] .
  2. HERE WE PRESENT A BIBLIOGRAPHY ON THIS SUBJECT OF TIDAL CYCLE RESONANCE. THE KEELING AND WHORF 2000 PAPER THAT CONSIDERS THE CLIMATE EFFECTS OF GRAVITATIONAL INTERACTIONS AMONG SUN, EARTH, AND MOON ONLY IS DESCRIBED IN SOME DETAIL BELOW. IT IS NOTED THAT OTHER PAPERS IN THE BIBLIOGRAPHY BELOW, VOISIN 2020 IN PARTICULAR, ALSO INCLUDE GRAVITATIONAL INTERACTIONS AMONG THE PLANETS – SPECIFICALLY THAT BETWEEN EARTH AND VENUS. 
  3. Tides are the creation of the gravitational interactions among earth, sun, and moon. This interaction is able to create the energy required to form tides on earth’s oceans. This energy is eventually released into the earth system and the gravitational interactions can also act as a perturbation of the earth’s internal geothermal heat in the mantle (Voisin 2020). Various papers by Keeling and Whorf and a few other authors (see Bibiography below) propose a mechanism in which periodic resonance in the gravitational interaction among earth, moon, and sun explains the cycles of millennial scale warming and cooling events over the 12,000 years of the Holocene that are described in a related post [LINK] . In that context, it is proposed by authors of tidal cycle papers that a study of the current warming period since the Little Ice Age should not exclude a role for tidal cycles.
  4. We now present a recent Keeling and Whorf paper [LINK] in some detail. The citation and abstract of the paper are as follows: CITATION: The 1,800-year oceanic tidal cycle: A possible cause of rapid climate change, Charles D. Keeling, WTimothy P. Whorf, May 2000, Proceedings of the National Academy of Sciences 97(8):3814-9, DOI: 10.1073/pnas.070047197, ABSTRACT: 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.
  5. THE FULL TEXT OF THE KEELING AND WHORF 2000 PAPER: A Proposed Tidal Mechanism for Periodic Oceanic Cooling. In a previous study (3) we proposed a tidal mechanism to explain approximately 6- and 9-year oscillations in global surface temperature, discernable in meteorological and oceanographic observations. We first briefly restate this mechanism. The reader is referred to our earlier presentation for more details. We then invoke this mechanism in an attempt to explain millennial variations in temperature. 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. As a measure of the global tide raising forces (ref. 5, p. 201.33), we adopt the angular velocity, γ, of the moon with respect to perigee, in degrees of arc per day, computed from the known motions of the sun, moon, and earth. This angular velocity, for strong tidal events, from A.D. 1,600 to 2,140, is listed in a treatise by Wood (ref. 5, Table 16). We extended the calculation of γ back to the glacial age by a multiple regression analysis that related Wood’s values to four factors that determine the timing of strong tides: the periods of the three lunar months (the synodic, the anomalistic, and the nodical), and the anomalistic year, defined below. Our computations of γ first assume that all four of these periods are invariant, with values appropriate to the present epoch, as shown in Table 1. We later address secular variations. Although the assumption of invariance is a simplification of the true motions of the earth and moon, we have verified that this method of computing γ (see Table 2) produces values nearly identical to those listed by Wood, the most serious shortcoming being occasional shifts of 9 or 18 years in peak values of γ. 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.As an indication that tidal forcing might influence temperature, Keeling and Whorf (3) found that times of cool surface temperature, on pentadal to decadal time-scales, tended to occur at 9-year intervals near events b and C of Fig. 1: thus, at times of strong 18.03-year Saros cycle tidal events. They occurred, however, at 6-year intervals midway between events b and C, when the Saros cycle events were weak and 6-year tidal forcing was more prominent than 9-year forcing. They also noted a general tendency for interdecadal warming near 1930, when Saros cycle forcing was weak, and a lack of warming when this forcing was strong near 1880 and 1970, as though cooling near times of strong forcing lingered for several decades, despite the identified events being only single tides.
  6. THE 1,800-YEAR TIDAL CYCLE: When the time-interval of computed strong global tidal forcing is extended to include all events from 500 B.C. to A.D. 4000 (Fig. 2), two longer periodicities become evident, defined by extensions of the maxima, labeled A–D and a–c, as in Fig. 1. First, near the beginning and end of the 4,000 years plotted, every second 180-year maximum is stronger, producing a periodicity of about 360 years. More striking is a well defined millennial cycle with maxima at 398 B.C., A.D. 1425, and A.D. 3107. The latter maximum is almost matched in strength, however, by one in A.D. 3452 such that a lesser intermediate event in A.D. 3248 appears to define the repeat period of the cycle as 1,823 years. The actual maximum in A.D. 3107, however, would define an interval of only 1,682 years.The existence of tidal forcing at intervals of about 1,800 years was proposed by Otto Petersson in 1914 and 1930 [cited by Lamb (ref. 6, p. 220)]. Cartwright (7) identified events similar to those plotted in Fig. 2, consisting of strong tidal forcing 93 years apart from A.D. 1340 to 1619 and again from 3182 to 3461: thus, an average interval between clusters of 1,842 years. Keeling and Whorf (3) briefly discussed the astronomical basis for an 1,800-year tidal cycle. Computations of γ over many millennia show this 1,800-year cycle and demonstrate that the spacing of maximum events is irregular. As we will show next, the cycle is well defined, however, with an exact average period when computed for the present epoch. The greatest possible astronomical tide raising forces would occur if the moon and the sun were to come into exact mutual alignment with the earth at their closest respective distances (7). If we only consider motions as they exist today (the present epoch) we can determine departures from this reference event as simple functions of the separation-intervals between four orbital conditions that determine these alignments and distances. The most critical condition is closeness in time to syzygy, a term that refers to either new moon or full moon. The return period of either lunar phase defines the 29.5-day synodic month. Maxima in tidal strength occur at both new and full moon: i.e., “fortnightly.” The next most critical condition of tidal forcing is the closeness of the moon to perigee, the point of the moon’s elliptical orbit closest to the earth. The fortnightly tides vary in strength as a function of the time-separation of perigee and syzygy. The moon is at perigee on average once every 27.6-day anomalistic month. When it is close to both perigee and syzygy, perigean tides occur. For each moon, new or full, this happens on average every 411.78 days, the beat period of the synodic and anomalistic months. A third important condition is the closeness of the moon to a node, either of two points in its orbit that lie on the ecliptic, the plane of the earth’s orbit around the sun. The moon crosses the ecliptic twice every 27.2-day nodical month. Maxima in perigean tides occur when the moon is close to the ecliptic, as well as to perigee and syzygy. This happens, on average, every 2.99847 calendar years to create the perigean eclipse cycle, equal to twice the beat period of the nodical and anomalistic months. The 6-year and 9-year tidal events that tend to correlate with times of cool global temperatures (3) are synchronous with every second or third perigean eclipse cycle, respectively. A fourth condition necessary for determining maximal tidal forcing is the closeness of the earth to perihelion, the point on the earth’s elliptical orbit closest to the sun, occupied every anomalistic year of 365.2596 days. When an analysis is made to find the times when all four conditions are most closely met, the 1,800-year cycle becomes apparent as a slow progression of solar-lunar declinational differences that coincide with progressive weakening and then strengthening of successive centennial maxima in tidal forcing (Fig. 2). The 1,800-year cycle thus represents the time for the recurrence of perigean eclipses closely matched to the time of perihelion. Progressively less close matching of perigee, node, and perihelion with syzygy occur, on average, at intervals of 360, 180, 90, 18, and 9 years. The long term average period of the 1,800-year cycle can be computed from the circumstance that the period of the perigean eclipse cycle falls 0.610061 days short of 3 anomalistic years. Independent of the condition of syzygy, the long term period is 1795.26 years (2.99847 × 365.2596/0.610061), equal to the beat period of the anomalistic year with one-third of the period of the perigean eclipse cycle. The actual timing of specific maximum events of the 1,800-year cycle depends, however, also on the timing of syzygy. This additional requirement causes the intervals between specific maxima to occur at intervals of 1,682, 1,823, or 2,045 years, or even occasionally ± 18.03 years from these three principal intervals. (An example is the 1,682-year interval from A.D. 1425 to 3107, noted above.) The maxima of the centennial cycles are also irregular. The 360-year cycle has principal intervals of 345, 363, and 407 years, plus occasionally others. The 180-year cycle has a wide range of intervals, in 9-year increments, from 141 to 204 years. The 90-year tidal interval can be either 84 or 93 years.
  7. A 5,000-YEAR MODULATION of the 1,800-YEAR CYCLE . A further millennial cycle arises from variability in the strengths of the maxima of the 1,800-year cycle. In the lowest plot of Fig. 3 is shown a hypothetical sequence of tidal events assuming, as a starting point, zero separation-intervals of syzygy from perigee, lunar node, and perihelion. The calculations assume that the lunar months and anomalistic year have constant periods appropriate to the present epoch. The γ value of all tidal events above a threshold of 17.150° per day are plotted. Every second or third 1,800-year maximum in γ is seen to be more prominent. The cause of this pattern can be understood by viewing the top plot of Fig. 3, which shows the separation-interval of syzygy from perihelion, in days, for all tidal events in the 360-year centennial cycle. This time-difference describes a pattern consisting of a generally declining difference interrupted by an abrupt upward shift that occurs 61 times in a simulation of 283,674 kyr (not all plotted): hence, an average period of 4,650 years. Shown in the middle plot of Fig. 3 is the departure, in arc degrees, of the moon from the plane of the ecliptic for the same events as shown in the upper plot. This angular difference describes a similar pattern to that of the upper plot, but with the average period of the 1,800-year cycle. The separation-interval of syzygy from perigee (not shown) remains small (less than 2 hr) for all of the maximum millennial events shown in Fig. 3. Thus, the 1,800-year cycle arises from progressive mismatches of syzygy and lunar node, the 4,650-year cycle from progressive mismatches of syzygy and perihelion. These two cycles are incommensurate even though both are expressed by recurring maxima of the 1,800-year cycle.
  8. Observational Tests of Millennial Tidal Climatic Forcing. Time-series of ice-rafted debris (IRD) from sedimentary cores in the North Atlantic ocean (1, 2), and associated temperature proxy data, show evidence of repeated rapid cooling events in the Northern Hemisphere, as summarized in “The 1- to 2-kyr IRD Cycle” section above. We now show, from results of both spectral analysis and direct comparisons of events, that strong oceanic tidal forcing may have occurred in association with IRD events. Spectral analysis of the IRD records, from 1- to 31-kyr BP, reproduced in Fig. 4 from Bond et al. (2), show broad peaks centered at 1,800 and 4,670 years (Fig. 4A), in contrast to an average pacing between IRD events of 1,470 ± 532 years. The peak periods agree closely with the 1,800-year and 5,000-year tidal cycle periods, shown by added vertical red lines. Bond et al. (2) also determined the phasing of the 1,800-year IRD band by filtering their data with a bandpass centered at 1,800 years (Fig. 4B). Cold periods, indicated by high filter values, nearly coincide with 1,800-year tidal events, shown by added horizontal red lines. A possible explanation for the disparity between the pacing of about 1,500 years, and the spectral period of about 1,800 years in the IRD data, is provided in Fig. 5 by a direct comparison of IRD cold events (dashed black lines) with times of strong tidal forcing (solid red lines). Between 0.6 and 31.2 kyr BP, 18 IRD events collectively exhibit an average spacing of 1,800 years while 4 others (“7”, “YD,” and one each near 14 kyr BP and 1.4 kyr BP) are spaced nearly midway between events of the first subset, 3 of these in a cluster near 12 kyr BP. The resulting bimodal pacing accounts for finding a broad spectral peak near 1,800 years, despite an average pacing of 1,470 years. Furthermore, the 1,800-year spectral peak is again found when the IRD record is extended back to 80 kyr BP (ref. 1, Fig. 8), with similar phasing of the associated bandpass. Additional clusters of events with about half the pacing of the majority again suggests a bimodal distribution in pacing.
  9. CONCLUSION OF THE KEELING AND WHORF PAPER: The details of the tidal hypothesis are complex. There is much about tidal forcing that we do not know, and there is not space here to discuss all that we do know that could contribute to proving whether it is the underlying cause of some, or all, of the events of rapid climate change. We are convinced, however, that, if the hypothesis is to a considerable degree valid, the consequences to our understanding of the ice-ages, and of possible future climates, are far from trivial. Should the tidal hypothesis of quasi-periodic cooling of the oceans turn out to be correct, a prevailing view that the earth’s postglacial climate responds mainly to random and unpredictable processes would be modified or abandoned. The 1,800-year tidal cycle would be recognized as a principal driver of climate change in the Holocene, causing shifts in climate more prominent and extensive than hitherto realized. The Little Ice Age would be seen to be only a lesser cooling episode in a series of such episodes. Viewed today as of “possibly global significance” (14), it would probably be confirmed as such, being linked to global tidal forcing. Other major climatic events since the glacial period, such as drought near the time of collapse of the Akkadian empire, might also be found to be linked to a global process.Looking ahead, a prediction of “pronounced global warming” over the next few decades by Broecker (15), presumed to be triggered by the warm phase of an 80-year climatic cycle of unidentified origin, would be reinterpreted as the continuation of natural warming in roughly centennial increments that began at the end of the Little Ice Age, and will continue in spurts for several hundred years. Even without further warming brought about by increasing concentrations of greenhouse gases, this natural warming at its greatest intensity would be expected to exceed any that has occurred since the first millennium of the Christian era, as the 1,800-year tidal cycle progresses from climactic cooling during the 15th century to the next such episode in the 32nd century.

WHORF2

[LINK TO FULL TEXT OF THE KEELING AND WHORF PAPER]

 

QUESTION: IS THIS THE SAME KEELING AS IN THE KEELING CURVE THAT AGW CLIMATE SCIENCE IS BUILT ON? ANSWER: YES

THE LATE GREAT KEELING AND THE LATE GREAT WHORF WERE CLIMATE DENIERS BECAUSE THEY HAD WRITTEN THAT WHILE AGW CLIMATE CHANGE EXPLAINS ONLY THE POST LIA WARMING, TIDAL CYCLES EXPLAIN ALL THE WARMING AND COOLING CYCLES OF THE HOLOCENE DESCRIBED IN A RELATED POST [LINK]   

 

 

 

 

Schematic chart about the spring-neap tidal variation in a lunar ...

TIDAL CYCLES  AND CLIMATE CHANGE BIBLIOGRAPHY

  1. 2020: Ronald Voisin, An Engineer’s Theory of Climate Change, [PDF DOWNLOAD]ABSTRACT: General Circulation Models of the climate have been developed by several countries of the world. These enormously expensive endeavors are alleged to include every imaginable climate forcing function. The authors of the Models assume that the Sun is the sole energy provider to the Earth climate system. And while the exothermic nature of the Earth is well recognized, it is further assumed that Earth’s internal heat generation is both temporally and spatially averaged to an inconsequentially small level, so as to be appropriately disregarded as a climatic issue. This misstep has led to the “CO2 is the climate control knob” meme. This essay re-asserts that constructive interference of gravitationally induced resonant modulations to the surface release of Earth’s internal heat generation are, in fact, the climate control knob on many, if not all, time scales. This essay further points to new Modeling directions that might more readily predict future climate events than current efforts are capable. IntroductionBroadly speaking, Earth’s climate alternates between two different states. One recurring state is commonly known as an Interglacial. It might well be considered a solar-albedo high-temperature latch. The Earth has been in this state for the last 11.5ky or so and this current interglacial is commonly known as the Holocene. These interglacials are relatively short lived periods characterized by relatively high solar absorption. Intrinsically these higher temperature periods are lower in entropy and therefore more difficult to achieve and sustain. But the relatively high solar absorption does, in fact, create a “latch” to this state, such that it should not be easily changed. The other recurring state is commonly known as glaciation. These relatively longer periods are characterized by relatively low solar absorption. Here too the relatively low solar absorption creates a “latch” such that this state should not be easily changed either. The causations to force transitions between these two “latched” states are of great interest. The down-temperature transition from interglacial to glaciation is lengthy and characterized by stair-stepping of a few degrees each step. This behavior is very difficult to explain in solar-radiative terms. However, the up-temperature transitions from glaciation to an interglacial are truly remarkable. These transitions are commonly known as de-glaciations (or glacial terminations) and they occur fantastically quickly in geologic terms. And as they occur, large solar-radiative forcing has to be overcome. To date, attempted explanations for these transitions have been almost entirely pursued in the solar- radiative domain only. This direction seems an impossible task. A new and very powerful climate driver is re-introduced herein called bulk-Earth-resonance. And this climate theory not only explains climate change on centennial and much longer time scales, but also on the most politically relevant decadal and annual time scales.
  2. 1989: Kvale, Erik P., Allen W. Archer, and Hollis R. Johnson. “Daily, monthly, and yearly tidal cycles within laminated siltstones of the Mansfield Formation (Pennsylvanian) of Indiana.” Geology17.4 (1989): 365-368. Whetstones (laminated siltstones) within the Mansfield Formation of Orange County, Indiana, are Lower Pennsylvanian (Morrowan) tidal deposits characterized by rhythmic laminations. Laminae thicknesses vary systematically in a vertical sequence and reflect tidal events of a mixed tidal regime. So complete is the record of tidal deposition that daily and monthly tidal cycles can be delineated. Neap-spring tides (related to the phases of the moon) and equatorial-tropical tides (related to the declination of the moon) are recognizable within the sequence.
  3. 1997: Keeling, Charles D., and Timothy P. Whorf. “Possible forcing of global temperature by the oceanic tides.” Proceedings of the National Academy of Sciences 94.16 (1997): 8321-8328. An approximately decadal periodicity in surface air temperature is discernable in global observations from A.D. 1855 to 1900 and since A.D. 1945, but with a periodicity of only about 6 years during the intervening period. Changes in solar irradiance related to the sunspot cycle have been proposed to account for the former, but cannot account for the latter. To explain both by a single mechanism, we propose that extreme oceanic tides may produce changes in sea surface temperature at repeat periods, which alternate between approximately one-third and one-half of the lunar nodal cycle of 18.6 years. These alternations, recurring at nearly 90-year intervals, reflect varying slight degrees of misalignment and departures from the closest approach of the Earth with the Moon and Sun at times of extreme tide raising forces. Strong forcing, consistent with observed temperature periodicities, occurred at 9-year intervals close to perihelion (solar perigee) for several decades centered on A.D. 1881 and 1974, but at 6-year intervals for several decades centered on A.D. 1923. As a physical explanation for tidal forcing of temperature we propose that the dissipation of extreme tides increases vertical mixing of sea water, thereby causing episodic cooling near the sea surface. If this mechanism correctly explains near-decadal temperature periodicities, it may also apply to variability in temperature and climate on other times-scales, even millennial and longer.
  4. 1999: Clark, Peter U., Robert S. Webb, and Lloyd D. Keigwin. Mechanisms of global climate change at millennial time scales. American geophysical union, 1999. Contributors describe the current understanding of abrupt climate variations that have occurred at millennial to submillennial time scales, events now recognized as characteristics of the global climate during the last glaciation. Subjects covered include analysis of modern climate and ocean dynamics, paleoclimate reconstructions derived from the marine, terrestrial and ice core records, and paleoclimate modeling studies. The breadth of global paleoclimate knowledge presented here provides information required to answer manypertinent questions related to climate change.
  5. 2000: Keeling, Charles D., and Timothy P. Whorf. “The 1,800-year oceanic tidal cycle: A possible cause of rapid climate change.” Proceedings of the National Academy of Sciences 97.8 (2000): 3814-3819. 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.
  6. 2001: Cerveny, Randall S., and John A. Shaffer. “The moon and El Nino.” Geophysical research letters 28.1 (2001): 25-28. Regional climates around the world display cycles corresponding to the 18.61‐year maximum lunar declination (MLD) periodicity. We suggest that these cycles are created by a relationship between MLD and El Niño / Southern Oscillation (ENSO). Both equatorial Pacific sea‐surface temperature and South Pacific atmospheric pressure significantly correlate with maximum lunar declination. Low MLDs are associated with warmer equatorial Pacific sea‐surface temperatures and negative values of the Southern Oscillation Index. A lunar‐influenced change in the Pacific gyre circulation presents a viable physical mechanism for explaining these relationships. We suggest that the gyre is enhanced by tidal forces under high MLDs, inducing cold‐water advection into the equatorial region but is restricted by the weak tidal forcing of low MLDs thereby favoring El Niño episodes. An astronomical model utilizing this relationship produces a forecast of increased non‐El Niño (either La Niña or neutral) activity for the early part of this decade.
  7. 2002: Munk, Walter, Matthew Dzieciuch, and Steven Jayne. “Millennial climate variability: Is there a tidal connection?.” Journal of climate 15.4 (2002): 370-385.Orbital forcing has long been the subject of two quite separate communities: the tide community is concerned with the relatively rapid gravitational forces (periods up to 18.6 yr) and the climate community with the long-period Milankovitch insolation terms (exceeding 20 000 yr). The wide gap notwithstanding, the two subjects have much in common. Keeling and Whorf have proposed that the millennial climate variability is associated with high-frequency tidal forcing extending into the 10-octave gap by some nonlinear process. Here, the authors distinguish between two quite distinct processes for generating low frequencies: (i) the “traditional” analogy with eclipse cycles associated with near coincidence of the appropriate orbital alignment of the Sun, the Moon, and Earth, and (ii) sum and differences of tidal frequencies and their harmonics producing low beat frequencies. The first process is associated with long time intervals between extreme tides, but the events are of short duration and only marginally higher than conventional high tides. With proper nonlinearities, (ii) can lead to low-frequency tidal forcing. A few candidate frequencies in the centurial and millennial band are found, which prominently include the Keeling and Whorf forcing at 1795 yr. This is confirmed by a numerical experiment with a computer-generated tidal time series of 275 000 yr. Tidal forcing is very weak and an unlikely candidate for millennial variability; the Keeling and Whorf proposal is considered as the most likely among unlikely candidates. Corresponding author address: Prof. Walter Munk, Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, University of California, San Diego
  8. 2002: Treloar, Norman C. “Luni‐solar tidal influences on climate variability.” International Journal of Climatology 22.12 (2002): 1527-1542. A possible exogenous cause of some terrestrial climate variability on time scales of 1 to 100 years is examined. Luni‐solar effects, and especially the coincidences of New Moon with small perigee distance, produce important tidal perturbations. These influences have been resolved in two orthogonal directions, and the variability in the southern oscillation and sea‐surface temperature anomalies may be at least partly understandable as a reflection of these tidal components. The correlation between tidal components and these climate factors is significant. The predictability of tidal effects may make a contribution to improving the accuracy and lead time of climate forecasting. Copyright © 2002 Royal Meteorological Society.
  9. 2002: Helmuth, Brian, et al. “Climate change and latitudinal patterns of intertidal thermal stress.” Science 298.5595 (2002): 1015-1017. The interaction of climate and the timing of low tides along the West Coast of the United States creates a complex mosaic of thermal environments, in which northern sites can be more thermally stressful than southern sites. Thus, climate change may not lead to a poleward shift in the distribution of intertidal organisms, as has been proposed, but instead will likely cause localized extinctions at a series of “hot spots.” Patterns of exposure to extreme climatic conditions are temporally variable, and tidal predictions suggest that in the next 3 to 5 years “hot spots” are likely to appear at several northern sites.
  10. 2003: Yndestad, Harald. “A lunar-nodal spectrum in Arctic time series.” ICES CM (2003). Spectral analysis shows that long time series of Arctic sea ice extent, te Kola temperature, and the NAO winter index show the signature of the 18.6-year lunar nodal cycle.
  11. 2004: Yndestad, Harald. “The lunar nodal cycle influence on the Barents Sea.” (2004). The Barents Sea contains one of the most productive marine areas in the world. For centuries, Northeast Arctic cod and Norwegian spring spawning herring have been of vital importance for the Norwegian fish export industry and hence economic growth in Norway. It has been common knowledge that the biomass of different Barents Sea species experiences both shortand long-term fluctuations. These fluctuations have been explained by changes in herring cycles and cod cycles, or by the introduction of new fishing equipment, and more. Norwegian marine research began in earnest at the beginning of the 19th century. The main task for researchers was to discover how nature influenced cod stocks and the effects these fluctuations had on the lives of people who depended on fishing for a living. Nearly 100 years later, scientists still disagree over the causes for the biomass fluctuations in the Barents Sea. At the same time, marine research has produced long time series, which can now be analyzed using new methods. This thesis represents an investigation of a number of long time series of Arctic climate indicators and biomasses in the Barents Sea. The purpose of this analysis has been to identify a potential stationary cycle in the biomasses. A stationary cycle in the biomass allows for expanded possibilities for better long-term biomass forecasting. The methods are based on general systems theory, analysis of systems dynamics and a wavelet analysis of time series. The wavelet analysis has identified the cycle time and the cycle phase of the dominant cycles in the time series. The phase-relation between the identified cycles contains information abort the dynamic chain of events between climate indicators and the biomasses in the Barents Sea. The investigation has identified harmonic and sub-harmonic cycles of the 18.6-year lunar nodal cycle in all analyzed time series. The identified lunar nodal spectrum is explained by a gravity force from the 18.6-year lunar nodal cycle as the First Cause. The energy from the 18.6-year gravity force from the moon introduces a chain of oscillating events. The oscillating gravity introduces a lunar nodal spectrum in the lunar nodal tide and the polar position. A wavelet analysis of time series indicates that movement of the polar position introduces a new lunar nodal spectrum of circulating water in the Arctic Ocean. This circulation water interacts with the 18.6-year lunar nodal tide in the Atlantic Ocean and introduces an oscillation in the extent of Arctic ice, and an oscillation in the inflow of the Atlantic Ocean to the Barents Sea. The lunar nodal spectrum of Atlantic inflow introduces a lunar nodal spectrum in the Barents Sea ecology system. Analysis of the biomass in the Barents Sea shows that long-term growth, reduction and collapse are associated with the phase-relation between the biomass eigen dynamics and the lunar nodal spectrum of Atlantic inflow.
  12. 2006: Yasuda, Ichiro, Satoshi Osafune, and Hiroaki Tatebe. “Possible explanation linking 18.6‐year period nodal tidal cycle with bi‐decadal variations of ocean and climate in the North Pacific.” Geophysical Research Letters 33.8 (2006). Bi‐decadal climate variation is dominant over the North Pacific on inter‐decadal timescale; however the mechanism has not been fully understood. We here find that the bi‐decadal variations in the North Pacific climate and intermediate waters possibly relate to the 18.6‐year period modulation of diurnal tide. In the period of strong diurnal tide, tide‐induced diapycnal mixing makes surface salinity and density higher and the upper‐layer shallower along the Kuril Islands and the east coast of Japan. Simple model results suggest that the coastal depth adjustment by baroclinic Kelvin waves enhances the thermohaline circulation, the upper‐layer poleward western boundary current and associated heat transport by about 0.05PW. This could also explain the warmer SST in the Kuroshio‐Oyashio Extension regions, where positive feedback with Aleutian Low might amplify the bidecadal variations. The 18.6‐year tidal cycle hence could play a role as a basic forcing for the bi‐decadal ocean and climate variations.
  13. 2006: Yndestad, Harald. “The influence of the lunar nodal cycle on Arctic climate.” ICES Journal of Marine Science 63.3 (2006): 401-420. The Arctic Ocean is a substantial energy sink for the northern hemisphere. Fluctuations in its energy budget will have a major influence on the Arctic climate. The paper presents an analysis of the time-series for the polar position, the extent of Arctic ice, sea level at Hammerfest, Kola section sea temperature, Røst winter air temperature, and the NAO winter index as a way to identify a source of dominant cycles. The investigation uses wavelet transformation to identify the period and the phase in these Arctic time-series. System dynamics are identified by studying the phase relationship between the dominant cycles in all time-series. A harmonic spectrum from the 18.6-year lunar nodal cycle in the Arctic time-series has been identified. The cycles in this harmonic spectrum have a stationary period, but not stationary amplitude and phase. A sub-harmonic cycle of about 74 years may introduce a phase reversal of the 18.6-year cycle. The signal-to-noise ratio between the lunar nodal spectrum and other sources changes from 1.6 to 3.2. A lunar nodal cycle in all time-series indicates that there is a forced Arctic oscillating system controlled by the pull of gravity from the moon, a system that influences long-term fluctuations in the extent of Arctic ice. The phase relation between the identified cycles indicates a possible chain of events from lunar nodal gravity cycles, to long-term tides, polar motions, Arctic ice extent, the NAO winter index, weather, and climate.
  14. 2006: Osafune, S., and I. Yasuda. “Bidecadal variability in the intermediate waters of the northwestern subarctic Pacific and the Okhotsk Sea in relation to 18.6‐year period nodal tidal cycle.” Journal of Geophysical Research: Oceans 111.C5 (2006). On the basis of historical oceanographic data, we investigated the long‐term variations of the intermediate waters in the four regions in the northwestern subarctic Pacific: Oyashio, Okhotsk Sea Mode Water, Upstream Oyashio and East Kamchatka Current. We found bidecadal oscillations in these water properties that are synchronized with the 18.6‐year period nodal cycle. In periods when the diurnal tide is strong, the following characteristics are found: Apparent oxygen utilization and phosphate are low in Oyashio and Okhotsk Sea Mode Water. The thickness of the intermediate layers is large, and thus potential vorticity is correspondingly low, in Oyashio, Okhotsk Sea Mode Water, and Upstream Oyashio. Around the mesothermal (temperature maximum) water, isopycnal potential temperature are low in the areas on the Pacific side, and high in the intermediate layer of Okhotsk Sea Mode Water. The mixing ratio of Okhotsk Sea Mode Water in the Upstream Oyashio water is high. These bidecadal oscillations can be explained by changes in the vertical mixing around the Kuril Straits induced by the diurnal tide whose amplitude is modulated with the 18.6‐year nodal cycle. Higher sea surface salinity water around the Kuril Straits caused by stronger tidal mixing is possibly transported northward along the cyclonic Okhotsk Sea Gyre, and possibly enhances the formation of the dense shelf water. This makes apparent oxygen utilization, phosphate, and potential vorticity lower in Okhotsk Sea Mode Water and Oyashio.
  15. 2007: Yndestad, Harald. “The Arctic Ocean as a coupled oscillating system to the forced 18.6 year lunar gravity cycle.” Nonlinear Dynamics in Geosciences. Springer, New York, NY, 2007. 281-290. The Arctic Ocean is a substantial energy sink for the Earth’s Northern Hemisphere. Future fluctuations in its energy budget will have a major influence on the Arctic climate. A wavelet spectrum analysis of an extensive historical Arctic data series concludes that we may be able to understand Arctic climate dynamics as an oscillation system coupled to the forced 18.6 yr lunar nodal gravity cycle. This paper presents the results from a wavelet spectrum analysis of the data series which included polar movement, Arctic ice extent and the inflow of North Atlantic Water to the Norwegian Sea. The investigation shows a correlation better than R = 0.6 between the astronomic 18.6 yr lunar nodal gravity cycle and identified 18 yr dominant cycles in the data series. The identified 18 yr cycles have phase – reversals synchronized to a 74 yr sub – harmonic lunar nodal cycle.
  16. 2007: McKinnell, Stewart M., and William R. Crawford. “The 18.6‐year lunar nodal cycle and surface temperature variability in the northeast Pacific.” Journal of Geophysical Research: Oceans 112.C2 (2007). The 18.6‐year lunar nodal cycle (LNC) is a significant feature of winter (January) air and sea temperatures along the North American west coast over a 400‐year period. Yet much of the recent temperature variation can also be explained by wind patterns associated with the PNA teleconnection. At Sitka, Alaska, (57°N) and nearby stations in northern British Columbia, the January PNA index accounts for over 70% of average January air temperatures in lengthy meteorological records. It appears that the LNC signal in January air temperatures in this region is not independent of the PNA, but is a component of it. The Sitka air temperature record, along with SSTs along the British Columbia coast and the PNA index have significant cross‐correlations with the LNC that appear at a 2‐year lag, LNC leading. The influence of the PNA pattern declines in winter with decreasing latitude but the LNC component does not. It appears as a significant feature of long‐term SST variation at Scripps Pier and the California Current System. The LNC also appears over centennial‐scales in proxy temperatures along western North America. The linkage of LNC‐moderated surface temperatures to processes involving basin‐scale teleconnections expands the possibility that the proximate mechanism may be located remotely from its expression in the northeast Pacific. Some of the largest potential sources of a diurnal tidal signal in the atmosphere are located in the western Pacific; the Sea of Okhotsk and the Indonesian archipelago.
  17. 2008: Yndestad, Harald, William R. Turrell, and Vladimir Ozhigin. “Lunar nodal tide effects on variability of sea level, temperature, and salinity in the Faroe-Shetland Channel and the Barents Sea.” Deep Sea Research Part I: Oceanographic Research Papers 55.10 (2008): 1201-1217. The Faroe-Shetland Channel and the Kola Section hydrographic time-series cover a time period of more than 100 years and represent two of the longest oceanographic time-series in the world. Relationships between the temperature and salinity of Atlantic water from these two areas are examined in this paper, which also presents for the first time comparisons between them and annual mean sea levels in the region. The investigation was based on a wavelet spectrum analysis used to identify the dominant cycle periods and cycle phases in all time-series. The water-property time-series show mean variability correlated to a sub-harmonic cycle of the nodal tide of about 74 years, with an advective delay between the Faroe-Shetland Channel and the Barents Sea of about 2 years. In addition, correlations better than R=0.7 were found between dominant Atlantic water temperature cycles and the 18.6-year lunar nodal tide, and better than R=0.4 for the 18.6/2=9.3-year lunar nodal phase tide. The correlation between the lunar nodal tides and the ocean temperature variability suggests that deterministic lunar nodal tides are important regional climate indicators that should be included when future regional climate variability is considered. The present analysis suggests that Atlantic water temperature and salinity fluctuations in the Nordic Seas are influenced by forced tidal mixing modulated by harmonics of the nodal tide and influencing the water mass characteristics at some point “down stream” from the Faroe-Shetland Channel. The effects of the modulated oceanic mixing are subsequently distributed as complex coupled lunar nodal sub-harmonic spectra in the thermohaline circulation.
  18. 2008: Hasumi, Hiroyasu, et al. “Pacific bidecadal climate variability regulated by tidal mixing around the Kuril Islands.” Geophysical Research Letters 35.14 (2008). 18.6‐year period variability has been detected in various aspects of the climate, especially in and around the Pacific Ocean. Although it is believed to be caused by 18.6‐year period tidal cycle, no study has directly shown how the tidal cycle regulates such variability. Using a state‐of‐the‐art climate model, we show that the 18.6‐year cycle in strong tidal mixing localized around the Kuril Islands induces 18.6‐year periodicity in El Nino‐Southern Oscillation‐like Pacific climate variability. Influence of the tidal mixing propagates along the Pacific western rim as coastally trapped waves. Temperature anomaly is generated in the subsurface western equatorial Pacific, which propagates along the equatorial thermocline and eventually excites 18.6‐year periodicity in the equatorial sea surface temperature.
  19. 2009: Yndestad, Harald. “The influence of long tides on ecosystem dynamics in the Barents Sea.” Deep Sea Research Part II: Topical Studies in Oceanography 56.21-22 (2009): 2108-2116. The Barents Sea ecosystem has been associated with large biomass fluctuations. If there is a hidden deterministic process behind the Barents Sea ecosystem, we may forecast the biomass in order to control it. This presentation concludes, for the first time, investigations of a long data series from North Atlantic water and the Barents Sea ecosystem. The analysis is based on a wavelet spectrum analysis from the data series of annual mean Atlantic sea level, North Atlantic water temperature, the Kola section water temperature, and species from the Barents Sea ecosystem. The investigation has identified dominant fluctuations correlated with the 9.3-yr phase tide, the 18.6-yr amplitude tide, and a 74-yr superharmonic cycle in the North Atlantic water, Barents Sea water, and Arctic data series. The correlation between the tidal cycles and dominant Barents Sea ecosystem cycles is estimated to be R=0.6 or better. The long-term mean fluctuations correlate with the 74-yr superharmonic cycle. The wavelets analysis shows that the long-term 74-yr cycle may introduce a phase reversal in the identified 18-yr periods of temperature and salinity. The present analysis suggests that forced vertical and horizontal nodal tides influence the ocean’s thermohaline circulation, and that they behave as a coupled non-linear oscillation system. The Barents Sea ecosystem analysis shows that the biomass life cycle and the long-term fluctuations correlate better than R=0.5 to the lunar nodal tide spectrum. Barents Sea capelin has a life cycle related to a third harmonic of the 9.3-yr tide. The life cycles of shrimp, cod, herring, and haddock are related to a third harmonic of the 18.6-yr tide. Biomass growth was synchronized to the lunar nodal tide. The biomass growth of zooplankton and shrimp correlates with the current aspect of lunar nodal tidal inflow to the Barents Sea. The long-term biomass fluctuation of cod and herring is correlated with a cycle period of about 3×18.6=55.8 yr. This analysis suggests that we may understand the Barents Sea ecosystem dynamic as a free-coupled oscillating system to the forced lunar nodal tides. This free-coupled oscillating system has a resonance related to the oscillating long tides and the third harmonic and superharmonic cycles.
  20. 2009: Yasuda, Ichiro. “The 18.6‐year period moon‐tidal cycle in Pacific Decadal Oscillation reconstructed from tree‐rings in western North America.” Geophysical Research Letters 36.5 (2009). Time‐series of Pacific Decadal Oscillation (PDO) reconstructed from tree‐rings in Western North America is found to have a statistically significant periodicity of 18.6‐year period lunar nodal tidal cycle; negative (positive) PDO tends to occur in the period of strong (weak) diurnal tide. In the 3rd and 5th (10th, 11th and 13rd) year after the maximum diurnal tide, mean‐PDO takes significant negative (positive) value, suggesting that the Aleutian Low is weak (strong), western‐central North Pacific in 30–50°N is warm (cool) and equator‐eastern rim of the Pacific is cool (warm). This contributes to climate predictability with a time‐table from the astronomical tidal cycle.
  21. 2010: Osafune, S., and I. Yasuda. “Bidecadal variability in the Bering Sea and the relation with 18.6 year period nodal tidal cycle.” Journal of Geophysical Research: Oceans 115.C2 (2010). Bidecadal variations are investigated in the Bering Sea, especially in the southeastern basin adjacent to the Aleutian passes, where vertical mixing may be strong because of the diurnal tide. Those variations found in this region are synchronized with the 18.6 year period nodal tidal cycle, and the temporal patterns are similar to ones around the northwestern subarctic Pacific near the Kuril Straits reported by a previous study. Salinity and density in the upper layer are high in the periods when the diurnal tide is strong. In the intermediate layer, layer thickness is large, and isopycnal potential temperature and apparent oxygen utilization are low in the same periods. It is shown that these variations are consistent with the patterns expected from the nodal modulation of vertical mixing, and a simple two‐dimensional model, assuming a balance between anomalous vertical mixing and advection of anomaly by the mean current, succeeds to some extent in explaining the variations of the upper layer salinity and isopycnal temperature and apparent oxygen utilization in the intermediate layer.
  22. 2012: Tanaka, Yuki, et al. “Effects of the 18.6-yr modulation of tidal mixing on the North Pacific bidecadal climate variability in a coupled climate model.” Journal of Climate 25.21 (2012): 7625-7642. Diapycnal mixing induced by tide–topography interaction, one of the essential factors maintaining the global ocean circulation and hence the global climate, is modulated by the 18.6-yr period oscillation of the lunar orbital inclination, and has therefore been hypothesized to influence bidecadal climate variability. In this study, the spatial distribution of diapycnal diffusivity together with its 18.6-yr oscillation estimated from a global tide model is incorporated into a state-of-the-art numerical coupled climate model to investigate its effects on climate variability over the North Pacific and to understand the underlying physical mechanism. It is shown that a significant sea surface temperature (SST) anomaly with a period of 18.6 years appears in the Kuroshio–Oyashio Extension region; a positive (negative) SST anomaly tends to occur during strong (weak) tidal mixing. This is first induced by anomalous horizontal circulation localized around the Kuril Straits, where enhanced modulation of tidal mixing exists, and then amplified through a positive feedback due to midlatitude air–sea interactions. The resulting SST and sea level pressure variability patterns are reminiscent of those associated with one of the most prominent modes of climate variability in the North Pacific known as the Pacific decadal oscillation, suggesting the potential for improving climate predictability by taking into account the 18.6-yr modulation of tidal mixing.

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