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Quasi-equilibrium in Holocene climatic change
Quaternary International, Vol. 2, pp. 83-89, 1989. Printed in Great Britain.
1040-6182/89 $0.00 + .50 1989 INQUA/Pergamon Press plc
QUASI-EQUILIBRIUM
IN H O L O C E N E
CLIMATIC CHANGE
R h o d e s W. Fairbridge
Department of Geological Sciences, Columbia University and NASA-Goddard Institute for Space Research, 2880 Broadway, New York 10025, U.S.A. To understand man's impact on the environment we should consider the long-term record. Within the Holocene epoch (approximately the last 10 ka), often regarded as having a uniformly mild 'interglacial-type' of climate, infrequent but violent fluctuations have disturbed this uniformitarian ideal. A quasi-equilibrium is maintained, however, by powerful feedback mechanisms. The precise nature of both the disturbance-forcing functions and the recovery mechanisms urgently requires study on an interdisciplinary basis, calling for a common-front approach by historians (for the best time scale), by geologists (for establishing the paleoecologlcai and paleogeographical conditions by means of isotopic, sedimentological and stratigraphic studies), and by climatologists (for modelling the meteorological, synoptic conditions that characterize the varied events). Five non-linear forcing agents may be considered in a framework of working hypotheses to help explain the climatic departures: (1) Volcanic eruptions (dust veils and aerosols); (2) lunar and iuni-solar tidal effects (variable standing waves in atmospheric pressure, modulation of ocean tides and currents); (3) terrestrial spin-rate and axial tilt (with secular change in precession, the 18.6 year axial rotation and the 1.2 year Chandler wobble); (4) oceanographic and glacial lag factors (influencing the chronology of latitudinal heat transfer; (5) solar radiation modulation of two principal types affecting the corpuscular pulses (solar flares), and the electromagnetic radiation (sunspot and Gieissberg cycles). This paper addresses particularly the last variable because this is the most neglected, and because new information has now become available thanks to new computer-based data sources.
INTRODUCTION The International Council of Scientific Unions has endorsed the concept of an International GeosphereBiosphere Programe (IGBP) with its first objective focussed on Global Change. This objective is outlined in a volume of the same name edited by Malone and Roederer (1984). Malone wrote about the origin of the program and Roederer about the main thrust of the anticipated research. In particular, the latter stressed linkage between terrestrial climate systems and (a) the biosphere and (b) the sun. Whereas present-day meteorological systems are habitually seen as random, dynamic fluctuations about a steady-state system, Roederer emphasized the non-linearity nature of the interactions and evolution. He remarked specifically upon the 'subtle perturbations introduced by the variability of solar corpuscular and short-wavelength radiation'. The first symposium of this program was held in Ottawa, in September 1984. This served as a forum for 'state-of-the-art' reviews which serve as a spring-board for the new research directions. Somewhat earlier in the same year (May 1984) another interdisciplinary symposium had been called together in New York City, at Columbia University, ostensibly to celebrate the writer's 70th birthday. The 'Festschrift' volume entitled Climate Change (edited by Rampino et al., 1987) brings together a wide selection of papers that mainly concentrate on the events and processes of the last 10 ka. If for no other reason, the volume may be useful for a 66 page bibliography. For the inquiring reader, interested in the history and philosophy of science, it may be seen from the citations that most fundamental ideas were already postulated more than a century ago. 83
Many of these ideas have been set aside in the twentieth century preoccupation with data acquisition, an activity that has been facilitated by the development of practical electronics, the computer, and space vehicles, This thrust of human energy and funds, while dazzling in its conceptual impact, has not been without drawbacks. In a recent article about the vast proliferation of data processing, generating information without digestion, H.R. Pagels (executive director of the New York Academy of Sciences) remarked: Information tends to drive out knowledge. Information is just signs and numbers, while knowledge involves their m e a n i n g . . .
The geologists enjoy a luxury that is not generally shared by physicists and chemists. They enjoy historical perspective - - over four billion years of it. This perspective has generated a favorite aphorism: 'What has happened, can happen!' This knowledge should not lull us into a sense of false security, allowing us to say 'We've seen it all before'. Quite the contrary, 'Time's Arrow' flies forever forward. It never goes back. But it flies up the central axis of a spiral staircase, the steps of which are the graduations of geological time, the punctuations of evolutionary history as recognized by Eldredge and Gould (1972). Seen in mathematical terms, this historical spiral is a cyclic sequence. In connection with an international conference on the disposal of radioactive waste the writer was once asked to spell out the fundamental laws that the earth's history has to contribute to the world of science. After much cogitation, whittling and consultation, we came up with only four 'Earth Laws' each of which carries various axioms and corollaries (Fairbridge, 1980). These laws, in a nutshell, state: 1. Law of Finite Existence. Our galaxy, solar sytem,
84
R.W. Fairbridge
Major planetary conjunctions are also observable with the naked eye, e.g. Chinese references to 'five stars in a line appeared like polished jade beads', apparently in the year -916 (917 BC) when Mercury, Venus, Mars, Jupiter, and Saturn were in very close alignment (also Uranus and Neptune, but these would hardly count as 'bright stars'). The weakness of such time markers is their scatter (incompleteness) and their verbal basis (liable to mistranslation). Recent papers by Stuiver, Pearson, Becker and colleagues (1986) now provide a dendrochronologic annual record and an internationally confirmed data bank of terrestrial signals of the radiocarbon flux-rate variations that permit sun--earth correlations (Eddy, 1977) to an accuracy of +10 years, the sample-interval of 14C analyses. Episodes of sun history when emission and radiation values fluctuated wildly can now be correlated with the dynamic conditions set up by certain planetary alignments. Those configurations have now been chronologically determined for about 12 ka. Calibration of radiocarbon-dated geological and cultural materials can now be made with respect to certain epochs, with an accuracy of better than 50 years. At other times (due to strongly fluctuating 14C flux) precision deteriorates badly, and dates obtained for those time-intervals must be treated with caution (Schove, 1987). Nevertheless, the main trends of Ho|ocene climatically related events can now be set within a fixed astronomic framework. A joint project by Fairbridge and Shirley (1987) undertakes to prepare relevant computer software for economically available disks that can be employed for general scientific use. The various planetary time series and solar orbital calculations, as well as the radiocarA TEN-THOUSAND-YEAR CLIMATE bon flux record, can all be supplied on standard 13 cm Geologists,climatologists and archaeologists are find- (51/4 inch) or 8.75 cm (31/2 inch) 'floppy' diskettes. ing themselves increasingly in need of a precise chronological framework for establishing stratigraphic, paleoANNUAL TIME SERIES climatic, and cultural events during the present geoBesides the long dendrochonoiogical series, there are logical time-unit, the Holocene epoch. The writer, with the aid of many colleagues, has now established an several types of year-by-year records in nature that can astronomical foundation for this calendar, based on the be used as terrestrial proxies of climatic fluctuations. In NASA-JPL long ephemeris (DE-102) of Newhall et al. certain favored locations the width and density of the (1983) and cross-checked against the ephemeris formu- tree-ring wood can be correlated with the solar lae of the U.S. Naval Observatory and of the European periodicities (Sonett and Suess, 1983), but more standard (Meeus and Victor, 1983). Preliminary papers frequently, though with fluctuating intensity, with the have been published (Fairbridge and Sanders, 1987; 18.6 year lunar declination cycle (Currie, 1987; Currie Fairbridge and Shirley, 1987). Dynamic analyses have and Fairbridge, 1985). been made by Jose (1965). Continuously counted, annually layered ice cores To be useful in archaeological or geological dating, an display cycles of oxygen-isotope variability, reflecting astronomical calendar requires certain clearly identifi- water-temperature changes in the snow's evaporation able marker dates, apart from the annual periodicity source areas (Johnsen et al., 1972). Those cycles which is clearly established (outside of equatorial strikingly correspond to the principal periodicities of latitudes) by seasonal change, and length of day and the major planets. Klaus (1980) has shown that for night. Such dates are observable, as in the periodicities several centuries the decades of 'cold' oxygen isotopes of Venus which were employed in a sophisticated way exactly matched those marked by droughts in West by the Mayans of Mexico. Eclipses of sun and moon Africa, and other studies show a relationship to were widely observed in the past and can be used to precipitation patterns in northeastern North America. An approximately 20-year periodicity in both the latter establish certain dates, provided the location is known. sun, planets, earth and moon are all constrained in terms of mass, size and time. Energy is exchanged between them in terms of electromagnetic radiation, particle transfer and angular momentum. When the sun eventually burns up, several billion years in the future, life on earth will terminate (but not before). 2. Law of Physical Evolution. In its 4.6 billion-year history planet earth has progressively evolved, mainly in threshold steps, and in complex cycles, but never exactly repeating itself. Its organized record in rocks grows more complicated throug h time, while retaining innumerable vestiges of past events. 3. Law o f Biological Evolution. Since the first self-~ reproducing molecule appeared about 4 billion years ago, no interruption has ever occurred in a progressively branching and more complex biota. No major phylum ever became extinct. 4. Law of Equilibrium. During the 4 billion years the mean global temperature has remained at 18 + 5°C and the equatorial sea-surface temperature stays at 30 + I°C, while the climate is constantly changing in complex cycles (from 1 day to several million years) but always maintained by positive and negative feedback mechanisms. This 'credo' is virtually unknown either by the physicists or the man-in-the-street. It thus seems appropriate to use it as an introduction to this essay, which will attempt to bring out two themes: (a) the need for an accurate year-by-year chronology in order to establish our historical record of the last 10 ka in a precise framework; and (b) to point the way towards future research into the astronomical basis for such a chronology.
Quasi-Equilibrium in HoloceneClimaticChange and the Greenland ice cores (Mook and Hibler, 1976) seems seductively close to the 19.85 year SaturnJupiter Lap, a s~,nodic 'metronome' that is dubbed 'the Pulse of the Solar System' (Fairbridge and Sanders, 1987), although a linkage mechanism is not yet established. With additional data on West African droughts, the writer has been able to extend the Klaus correlation with the Greenland isotopic record by several more centuries. Another type of annual layering that displays climatic cycles of oxygen isotope variations is found in the seasonal banding of stalactite accretion, but no cave appears to carry a continuous record spanning the whole of the Holocene. Furthermore, this type of study is difficult to pursue because the integrity of the stalactites is usually jealously defended by the guardians of the various caves. After the tree rings, the most important annual layerings are those found in lacustrine varved clays. These are widespread in formerly glaciated regions, but require an enormous investment in time and money in boring the various lake basins and closely measuring the layer thickness. This investigation, begun nearly a century ago in Sweden by the Baron de Geer, has recently been rechecked and coordinated to the contemporary dates by Cato (1985). As climatic proxies the varves only reflect events within the limits of a particular basin, and then generally provide only an indication of the spring melt of the preceding winter's snow. Nevertheless, cycle analysis and correlations with tree-ring thicknesses carried out in Finland (Sirrn and Hari, 1971), show an approximate uniformity in northeast Scandinavia. The most important cycles are the luni-solar beat frequencies (such as the 93 year frequency). Marine varves are known, but only in certain favored areas. Normally, in well oxygenated basins, the bottom life will plough up the sediment of the sea floor ('bioturbation') in a way that tends to homogenize the signal. The result is usually a biogenic 'smoothing' over an interval of 1-3 ka, which is exactly in the zone of signals we are seeking to discover. In some favored basins, however, the bottom environment is anoxic and biologic scavengers are thus excluded. High latitude sites are contaminated and disturbed by 'ice rafting' (boulders and debris dropped from melting icebergs or sea ice). Intermediate latitudes marked by strong seasonality are ideal. Anoxic basins of this sort have been found off southern California and in the Gulf of California (Mexico). Calibration problems exist, but the work published so far is very promising (Pisias, 1978). COASTAL RADIOCARBON SAMPLES
A large number of studies have been made of coastal marine areas where a rich variety of different sediments can be subjected to various paleotemperature and other types of analysis, including radiocarbon dating. If the information needed is limited to a precision about +500 years there is little problem with the laboratory
85
'age'. The appraisal of the sample, its potential contamination, and the calibration to 'calendar' (sidereal or astronomical) years requires great care, however Literally thousands of dates are published that purport to represent the age of a high sea level in the range of 15-35 ka BP. Almost all of these, alas, reflect varying degrees of minor contamination, and there is today strong evidence that throughout that period the world sea level was in the range of 50-135 m below that of today. Neotectonics, including glacioisostatic crustal recovery, leads to widespread elevation anomalies but in the latitudes from which most of the samples are collected the implied rate of sustained vertical crustal motion (5-10 mm/year) would be distinctly unusual. Frequently in the same area there are also coastal formations of Eemian (Tyrrhenian) age, i.e. around 80-130 ka, that display little evidence of tectonic disturbance and are commonly quite horizontal over large distance at elevations in the range of 3-8 m above present MSL. If these late Pleistocene formations are not greatly displaced, then the younger, lac dated littoral facies cannot have suffered great vertical disturbances. It is quite illogical to claim Holocene crustal adjustments if Pleistocene rocks are undisturbed. As regards the materials sampled in these Holocene coastal assemblages, the most reliable are generally charcoals associated with coastal middens. They also provide an opportunity for controlling the midden shell dates. If the latter are of marine mollusca, there is always the possibility of their contamination by 'old water' brought to the surface by upwelling (particularly common in the Arctic, Peru and California). In such events the dates may be 300--600 years too old. Shells from the top of the midden may have been added over the centuries and correspondingly may give ages that are too young with respect to the shoreline. In barrier beach (beachridge) sequences, the shells and especially shell debris may be reworked from older beaches; where multiple dates are available in such cases, the youngest in any series is most likely to be correct. Driftwood samples in beach sequences are often too old, especially from the Arctic. Peat and wood samples (especially mangrove roots) from back-beach swamps and lagoons are likely to give reliable dates, except that care is needed to assess potential contamination by younger roots. Articulated shells from lagoons are clearly in growth positions and generally provide useful dates. When it comes to calibration, from radiocarbon years (often best indicated with Schove's convention 'year BP') to calendar years, reference should be made to the chronological diagrams in the papers by Stuiver and several others (in Radiocarbon, 28, 1986). It will be seen that in certain time spans the indicated date is likely to be accurate in the range of _ 10-20 years. At other times, due to protracted periods of strongly oscillatingl4C flux values, there may be an interval of 200 years or more when a wide range Of error (several centuries) must be expected. When attempting to reconstruct an astronomical chronology a large number
86
R.W. Fairbridge
of these dates should be set aside at first; after the chronological framework is built up from a very small number of closely screened (and hopefully 'accurate') dates, then the dates from the isotopically disturbed periods can be added to the record with the proviso that they are 'not incompatible' with the model presented. In no circumstances should dates of different samples be averaged; indeed, different molluscan species should not be mixed. A half-dozen 'good' dates are worth more than a hundred dubious ones. Sophisticated statistical procedures are often no better than computational electronic 'muscle-flexing'. MARINE STRATIGRAPHIC MODEL
Presented here is a very preliminary model of a Holocene chronology based upon three assumptions, or working hypotheses: (a) that major planetary fluctuating conjunctions determine episodes of low or strongly fluctuating solar emissions and radiation; (b) that these episodes are recorded on earth by high 14C flux interval.s as identified in tree-rings; and (c) that the incoming particulate solar energy is partly screened by the body of the moon and is modulated by the earth's magnetic field, short-time variations of which are believed to be caused by declination variables of the moon, the Chandler wobble and fluctuations in the terrestrial spin rate. Three extra-terrestrial forcing functions are thus envisaged, two from the sun and one relating to motions of the moon. The chronologies involved can be accurately calculated, but the amplitudes of the postulated effects can only be stated in generalized terms at the present juncture. The sun's electromagnetic radiation, in the optical and infrared wavelengths, is close to being constant, although a small variance through the ll-year sunspot cycle may be expected. In contrast a large variance through this same period is observed with respect to the extremely high UV spectrum. This is responsible for generating ozone in the stratosphere, where it is the principal 'greenhouse' agent, affecting the thermal conditions and the physical height of the stratopause in low latitudes. Ozone concentration, measured by rockets over the last 3 decades or so, shows a marked fluctuation with the sunspot cycle, but during the last solar minimum it appears to have fallen appreciably more than expected, due to anthropogenic pollution. Nevertheless, from observations in the high Alps at Arosa (Switzerland), in spite of large fluctuation, there is no overall change (e.g. Diitseh, 1979). As concerns the partiele radiation (maximum during solar flares), high-latitude disturbances to the general circulation are triggered (Bucha, 1984). Both flares and the earth's spin and Chandler wobble relate to planetary dynamics, notably the Jupiter--earth-Venus alignments, every 5.55 years. ENHANCEMENT YEARS AND ACTIVITY SPIKES Most of the proxy climatic series mentioned earlier
disclose a condition approaching that of a steady state. Departure from that mean is engendered by varied agencies, the astronomically based ones being predictable (see Table 1)0 The principal disturbing processes include: (1) Catastrophic type events, such as volcanic eruptions that generate dust veils and aerosols (each one differing from the last in terms of dimensions, material, latitude, season and so on) and, although expectable, they are-hardly predictable in an exact chronological sense. Another catastrophic type of disturbance is the threshold-type outbreak of flooding due to glacierdam withdrawal or tilting. (2) Lunar and luni-solar tidal effects, both atmospheric and oceanic, are reasonably predictable. Due to crustal loading (by tidal, shelf waters), as well as earth tides, some earthquakes and volcanic eruptions are also affected by these influences. Through tidally influenced ocean-current variations, sea-surface temperatures (SSTs) are sometimes subject to quite large changes; the associated steric (thermal, water-volume) effect is demonstrated by tide gauges. (3) The spin axis of the earth undergoes a wellknown 1.2 year nutation, known as the Chandler Wobble. As noted by Currie and Fairbridge (1985) a beat frequency of 6.2 years develops that is recorded in almost all climatic proxies. Furthermore, there are frequent short-term changes of spin rate, some of which are clearly related to climate and some to the solar wind or other exogenetic agencies. Long-term ('secular') change in the earth's axial orientation, affecting the seasons and thus the entire global climate, is related to the precession of the perihelion (20,969 years). This periodicity is an exact multiple of the various shortterm astronomic variables (e.g. 16 x 19.859 years Saturn-Jupiter Lap; 66 x 317.7 year Solar Angular Velocity Cycle; 1112 x 18.613 year Lunar Nodal Cycle). (4) Short-term or abrupt departures tend to be spread out or delayed by multiple oceanographic and glacial lag factors and enhanced or retarded by dynamic feedback mechanisms. As the mean oceanic turnover time is of the order of 500 years or more, some of the latitudinal heat exchanges on the globe tend to exceed in length many of the cyclic changes that initiate them. (5) Until recently the concept of a cyclic variance of solar radiation was opposed by the 'establishment', and so far only the present solar cycle values have been measured beyond any reasonable doubt. Nevertheless, it may now be assumed that such variance must also have been true for earlier cycles, and in varying degrees, depending upon a range of potential indicators. In the historical era, documentary evidence of auroras is generally accepted as persuasive. For the Holocene in general the radiocarbon flux rate obtained from dendrochronological series seems to be a reasonably consistent indicator of solar activity. In the course of each solar cycle the interaction between the solar wind and the earth's magnetic field modulates the galactic cosmic ray flux in such a way that the high solar
87
Quasi-Equilibrium in Holocene Climatic Change TABLE 1. Holocene astrophysical chronology {1)
C-14 FLUX MAX.
=low SOL act) [¢10 yr]
MIN, (=high sol. act.) [-+10 yr]
(2) PLANETARY
SOLAR FACTORS
Major Conjunctions 317,7 yr 45.37 etc
Saturn-Jupiter Lunar C. 997.8 yr
(3)
LUNAR TIDAL
(8) 111 yr,
ANO
LUN I-SOLAR FACTORS
(b) 18.6 yr.
(c) 16.03 yr
1615
1749 1623
(4)
Marine Stratigraphy Riae - Fall
TERRESTRIAL PROXIES
C - 14
Pollen Zones "Ages" B.P
A.D 2 kyr
1 ky
1751
1761 1626 1530
1630
1624
1370
1442 1306"
1452
1306
1125
1155
8O9
857
990 900 807
1447
1443 1298 1154 1118
<
) •
<
1
SA-2 < )
865 812
-1100 ±150
685 560
560
555 498
563 491
3
34 -4 -143
256 166 36 -17 -144
491
430
)
390 261
260 173 30
AD -143 -250
173 35 -6 -140
-35
SA-1
-2100
-210 -334
-342 -468
-462 -550 -600 -780
-642 -778
-632
-916" -1096
-646
-649 -744
-929
-926
-918 -1098
-1227
-1242
-1242
-774
-870 1 kyl
-960 -1095
> SB-2
-1170 -1370 -1416 -1662
-1670 -1790
-1733
-2010 -2120 *2260
-1735
-1728 -1918
-2052
-2054 -2124 -2178 -2358 -2412 -2557
-1823
-1850 -2 kyl
-1422 -1530
-1525
-1530
-2150
-2050 -2187
-2121
-2366 -2450 -2550
-2419 -2510
-2554
-2716
-2790
-2719 -2864
-2865
-2850 - 3ky
-2560
-2548
-3010
-3050
-3003 -3131
-3015
-3280 -3320
-3390
-3321"
-3312
-3328
-3002
-3009 -3136
-3316
-3316
-3610
-3602
-3908
-3819 -3910
-3818 -3940 -4050
- 4 kyr -4280
-4136
-4135 -4274
-4206
-4454 -4591
-4504
-4350 -4450 -4600
-4630
-4930
-4950
-4452
-4127 -4213 -4269 -4409 -4593 -4819
- 5kyl
-4863 -4953 -5090
-4802
.9. -----~
SB-1
> -5200
>
AT-2
-4806 -4901
-5100
-5190 -5230 -5360
~3800
-5104
-5103
-5100
-5698
-5695 -5730 -5857
-5397 6600 :250
-5405 -5695 -5720 -5900
- 6 kyr
-5950
-5728 -5863 -5993
-5993
AT-1
-6001
NOTES: " -NUSJ Lap (2222 yr - 49 x 45.37 - 7 x 317; 24505 y r . 53 x 45.37) Period 317.7 - 7 x 45.37 (HudSon Bay ato~0~sa cy~e) Period 297 8 - 6.2 (Chandler Wobt~4 beet: 9enmal climate t i t l e ) Period 111 = { Luni-Sotgr - Pehhelion Tide). 9g x 1132 - 20 • S,5S (JEV Lap)
Column 1. High and low peaks of radiocarbon flux in tree rings (Stuiver and others, 1986). Samples generally reflect a precision of _+ 5-10 years. Actualistic significance is suggested by the peak episodes (low solar radiation and weak geomagnetic field) corresponding to El Nifio years, by catastrophic droughts in the Sahel andby monsoon failure in India. In mid-latitudes the solar weakness is reflected by abrupt and extreme climatic fluctuations (higher and lower than normal; tree rings alternatively very wide and very narrow). Column 2. Planetary-solar cycle correlations. Although the variance of most of the planetary cycles is less than _+ 1 year, most of the synodic (lap) rates of the major planets are greater than 10 years and tend to alternate in length, so that exact coincidences are not expected. The longitudinal shift of the outermost planets is only a few degrees a year. Column 3. Principal lunar periodicities (see Table 2 for typical phase relationships and correlations with the planetary-solar periods). Column 4. General transgressive or regressive trends in marine coastal stratigraphy. Transgressions are marked by superposition over paleosols, fluvial or lagoonal sediments; regressions generally by deltaic progradation, often associated with widespread (slightly diachronons, peat layers. This stratigraphy is best preserved in tectonicaily negative, subsiding situations. In uplift areas, the evidence is generally limited to beach ridges. Pollen zones are designated SA (sub-Atlantic), SB (sub-Boreal), and AT (Atlantic).
88
R . W . Fairbridge
activity phase is reflected by low radiocarbon production. Tree-ring growth widths, in favored living areas, are now found to vary in phase with the sun's activity cycles, showing that climate is directly modified by those variations. From the above summary, it is clear that certain days, months, years, or decades are characterized by particular events, 'spikes', or fluctuations, and from study of appropriate astronomical data those events are
predictable. Such predictions can be tested against the historical and geological records. Table 2 illustrates how certain epochs are characterized by clusters of planetary, solar and lunar events. They may be called 'enhancement years' which recognize that solar and terrestrial stresses are brought to bear, enhancing the usual reactions. It should be emphasized that these studies are still in their infancy, and at the present juncture, the author's role is merely exploratory.
T A B L E 2. E n h a n c e m e n t years A D 835-2001, integrating solar and lunar periodicities
A-1 SUNSPOT MAX.
A-2 CYCLE MIN.
[2001] 1987 1969 1913 1894 1856 1838 1784 1727 1689 1650 1633 1615 1578 1558 1466 1450 1430 1411 1392 1356 "1340" 1318 1297 1281 1261 "1246" "1227" "1 209" 1168 1149 1111 1093 "1 036" 1003 981 962 946 925 910 872 851 835
B-1 B-2 LUNAR CYCLES Nodal Aplldes 18.6 y r . 8.647 yr.
B-3 Chandler 6.2
yr.
2006.5 1987.8 1969.2 1913.4 1894.8 1857.6 .1838.9 1783.1 1727.3 1690.0 1652.8 1634.2 1615.6 1578.4 1559.7 1466.7 1448.0 1429.4
2005.3 1987.6 1969.9 1916.8 1890.2 1854.9 1837.2 1784.0 1730.9 1686.7 1651.4 1633.7 1615.9 1580.6 1582.9 1465.6 1447.9 1430.2
2004.9 1986.4 1967.7 1911.9 1893.3 1856.1 1837.5 1781.7 1725.8 1688.6 1651.4 1632.8 1614.2 1576.9 1558.3 1465.3 1446.7 1428.1
1410.8 1392.2 1354.9 1336.4 1317.7 1299.1 1280.5 1261.9 1243.3 1224.7 1206.1 1188.9 1150.3 1113.0 1094.4 1038.5 1001.4 982.7 964.1 945.5 926.9 908.3 871.1 852.4 833.8
1412.5 1394.8 1359.4 1341.7 1315.2 1297.5 1279.8 1262.1 1244.4 1226.7 1209.0 1164.8 1147.1 1111.7 1093.9 1032.1 1005.5 978.9 961.8 943.6 925.9 908.2 872.8 855.1 837.4
1409.5 1390.9 1359.9 1335.1 1316.5 1297.9 1279.3 1260.7 1242.1 1223.5 1204.9 1167.7 1149.1 1111.9 1093.3 1037.5 1000.3 981.7 963.1 944.5 925.9 907.3 870.1 851.5 832.9
C1, 83
2, 3, 4, 5 PLANETARY- SOLAR 93 111 178 297
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e
N o te : " d a t e s uncertain; square brackets-phase reversal
Explanation: Selected years (mostly at _+ ! year precision) are presented here to illustrate the m a n y ways in which a particular interval in the astronomic chronology m a y be subject to multiple influences. A modest stress is thus liable to accumulate by successive feedbacks and e n h a n c e m e n t processes; these stresses are applied to the sun by the planets (86% of their angular m o m e n t u m is clue to Jupiter and Saturn), and by the sun and m o o n to the earth. In columns A-1 and 2 (sunspot maxima and minima) the precision drops off for years earlier than the 15th century, and dubious dates are indicated by parentheses. In c o l u m n s B-1-3 (lunar cycles) the nodal a n d apsides values are very regular, but the Chandler wobble beat frequency (6.4 years; 3 x 6.2 = 18.6) has an intercycle variance of _+ 1 year. in c o l u m n s C-1-6 all the periods are ultimately commensurable: e.g. 83.3 years (heliomagnetic a n d flare cycle = 7 x 11.86, 15 x J E V lap; 2 x 83.3 = 9 x 18.6 - 1112 years - 56 SJL -- 24.5 U S L = 87 N J L = 200 J E V L ) ; 93 years (perigee-syzygy-perihelion cycle b 5 x 18.6 = 10.5 x 8.847 = 15 x 6.2 = 3.31); 111 years (extreme PSP cycle = 20 x 5.55, J E V L = 10 x 11.1 sunspot cycle = 100 x 1.1 lunar tide); 178.71 years (sun's orbital s y m m e t r y progression a n d 'All Planet Synod' ,= 9 x 19.859 S.IL = 9.6 x 18.61); three examples of 297.2 year (luni-solar-Jupiter-Saturn beat: 18.61/19.859; 297.85 -- 16 x 19.859 = 17 x 18.61); two examples of 317.71 years ( m e a n U r a n u s - S a t u r n - J u p i t e r Lap; s u n ' s angular velocity max./min./period -- 7 x 45.37 U S L = 16 x 19.859 S,IL). C o l u m n D - - illustrates examples of the luni-solar combination of the "All C o m p o n e n t ' Gabriel Cycle of 744.5 years (40 x 18.6, 8 x 93; 18 x 744.5 -- 13.403 = 75 x 187.7 = 45 x 297.85 = 5 x 2680.7, the ' J u p i t e r - S a t u r n R e s o n a n c e Drift').
Quasi-Equilibrium in Holocene Climatic Change
89
Fairbridge, R.W. and Sanders, J.E. (1987). The sun's orbit, AD 7502050: basis for new perspectives on planetary dynamics and earthmoon linkage. In: Rampino, M.R., Sander, J.E., Newman, W.S. A few, but very important people have inspired and encouraged and Krnigsson, L.-K. (eds), Climate: History, Periodicity and the author in this work. They include the late Derek Schove (West Predictability, pp. 446--471 (with extended bibliography, pp. 475Wickham, U.K.), who pioneered the sunspot-aurora-weather story; 541). Van Nostrand Reinhold, New York, U.S.A. John Sanders (Columbia University, New York) who started me Fairbridge, R.W. and Shirley, J.H. (1987). Prolonged minima and plotting solar orbits; Eric Olausson (Gothenburg, Sweden) who the 179-year cycle of the solar inertial motion. Solar Physics, !10, introduced me to the tidal work of Otto Pettersson; Bob Currie 191-220. (Stony Brook, New York) who showed me the 18.6 year cycle in Johnsen, S.J., Dansgaard, W., Clausen, H.B. and Langway, C.C. Jr. multiple proxy series; Fergus Wood (San Diego) who demonstrated (1972). Oxygen isotope profiles through the Antarctic and Greenthat coastal flooding was tidally predictable; and not least, Jim land ice sheets. Nature, 235, 429--434. Hanson, who invited me to enjoy the facilities and inspiration of Jose, P.D. (1965). Sun's motion and sunspots. The Astronomical NASA's Goddard Institute for Space Studies. Journal, 70, 193-200. This study was partly supported by an N.S.F. grant CES - 8618525, Klaus, D. (1980). Paleoecology of Africa, 12, 315. 'Operation Noah'. Malone, T.F. and Roederer, J.G. (1984). Global Change, 512 pp. Cambridge University Press, Cambridge, U.K. Meeus, J. and Victor, R.C. (1983). Astronomical Tables of the Sun, Moon and Planets. Willmann-Bell, Richmond, Virginia, U.S.A. REFERENCES Mook, S.J. and Hibler, W.D. (1976). The 20-year oscillation in eastern North America temperature records. Nature, 261,484--486. Bucha, V. (1984). Mechanisms for linking solar activity to weather- Newhall, X.X., Standish, E.M. Jr. and Williams, J.G. (1983). DE102: a numerically integrated ephemeris of the Moon and scale effects, climatic changes and glaciations in the northern planets spanning forty four centuries. Astronomy and Astrophyhemisphere. In: Mrrner, N.-A. and Karlrn, W. (eds), Climatic sics, 125, 150-167. Changes on a Yearly to Millennial Basis, pp. 415 448. D. Reidel Pearson, G.W. and Stuiver, M. (1986). High-precision calibration of Publishing Company, Dordrecht, The Netherlands. the radiocarbon time scale, 500-2500 BC. Radiocarbon, 28, 839Cato, I. (1985). The definitive connection of the Swedish geochrono862. logical time scale with the present, and the new date of the zero Pisias, N.G. (1978). Paleoceanography of the Santa Barbara Basin year in D6viken, northern Sweden. Boreas, 12, 117-122. during the last 8,000 years. Quaternary Research, 10, 366-384. Currie, R.G. (1987). Examples and implications of 18.6- and ll-year Rampino, M.R., Sanders, J.E., Newman, W.S. and K6nigsson, L.terms in world weather records. In: Rampino, M.R., Sanders, K. (eds) (1987). Climate: History, Periodicity and Predictability. J.E., Newman, W.S. and K6nigsson, L.-K. (eds), Climate: 588 pp. Van Nostrand Reinhold, New York, U.S.A. History, Periodicity and Predictability, pp. 378--403. Van Nostrand Rhodes, F.H.T. (1983). Gradualism, punctuated equilibrium and the Reinhold, New York, U.S.A. Origin of species, Nature, 305, 269-272. Currie, R.G. and Fairbridge, R.W. (1985). Periodic 18.6 year and Schove, D.J. (1987). Sunspot cycles and weather history. In: cyclic I 1-year induced drought and flood in northeastern China and Rampino, M.R., Sanders, J.E., Newman, W.S. and K6nigsson, some global implications. Quaternary Science Reviews, 4, 109-134. L.-K. (eds), Climate: History, Periodicity and Predictability, pp. Diitsch, H.U. (1979). The search for solar cycle--ozone relationships. 355-377. Van Nostrand Reinhold, New York, U.S.A. Journal of Atmospheric and Terrestrial Physics, 41,771-785. Eddy, J.A. (1977). Historical evidence for the existence of the solar Sirrn, G. and Hari, P. (1971). Coinciding periodicity in recent tree rings and glacial clay sediments. Finland, Kevo Subarctic Research cycle. In: White, O.R. (ed.), The Solar Output and its Variation, Station, Reports, 8, 348-352. pp. 51-71. Colorado Associated University Press, Boulder, ColoSonett, C.P. and Suess, H.E. (1983). Correlation of bristlecone pine rado, U.S.A. ring widths with atmospheric ~4C variations: a climate-sun relaEddy, J.A., Gilliland, R.L. and Hoyt, D.V. (1982). Changes in the tion. Nature, 307, 141-143. solar constant and climatic effects. Nature, 300, 689--693. Stuiver, M. (1980). Solar variability and climatic change during the EIdredge, N. and Gould, S.J. (1972). In: Schopf, T.J.M. (ed.), current millennium. Nature, 285, 868-871. Models in Paleobiology, pp. 82-115. Freeman Cooper, San Stuiver, M. and Pearson, G.W. (1986). High precision calibration of Francisco, California, U.S.A. the radiocarbon time scale, AD 1950-500 BC. Radiocarbon, 28, Fairbridge, R.W. (1980). Prediction of long-term geologic and 8O5-838. climatic changes that might effect the insolation of radioactive waste. In: Anon. (ed.), Underground Disposal of Radioactive Stuiver, M., Pearson, G.W. and Braziunas, T.F. (1986). Radiocarbon age calibratio, i of marine samples back to 9000 cal. year BP. Waste, Vol. 2, pp. 385--405. International Atomic Energy Agency , Radiocarbon, 28, 980-1021. (IAEA-SM 243143), Vienna, Austria. ACKNOWLEDGMENTS
1040-6182/89 $0.00 + .50 1989 INQUA/Pergamon Press plc
QUASI-EQUILIBRIUM
IN H O L O C E N E
CLIMATIC CHANGE
R h o d e s W. Fairbridge
Department of Geological Sciences, Columbia University and NASA-Goddard Institute for Space Research, 2880 Broadway, New York 10025, U.S.A. To understand man's impact on the environment we should consider the long-term record. Within the Holocene epoch (approximately the last 10 ka), often regarded as having a uniformly mild 'interglacial-type' of climate, infrequent but violent fluctuations have disturbed this uniformitarian ideal. A quasi-equilibrium is maintained, however, by powerful feedback mechanisms. The precise nature of both the disturbance-forcing functions and the recovery mechanisms urgently requires study on an interdisciplinary basis, calling for a common-front approach by historians (for the best time scale), by geologists (for establishing the paleoecologlcai and paleogeographical conditions by means of isotopic, sedimentological and stratigraphic studies), and by climatologists (for modelling the meteorological, synoptic conditions that characterize the varied events). Five non-linear forcing agents may be considered in a framework of working hypotheses to help explain the climatic departures: (1) Volcanic eruptions (dust veils and aerosols); (2) lunar and iuni-solar tidal effects (variable standing waves in atmospheric pressure, modulation of ocean tides and currents); (3) terrestrial spin-rate and axial tilt (with secular change in precession, the 18.6 year axial rotation and the 1.2 year Chandler wobble); (4) oceanographic and glacial lag factors (influencing the chronology of latitudinal heat transfer; (5) solar radiation modulation of two principal types affecting the corpuscular pulses (solar flares), and the electromagnetic radiation (sunspot and Gieissberg cycles). This paper addresses particularly the last variable because this is the most neglected, and because new information has now become available thanks to new computer-based data sources.
INTRODUCTION The International Council of Scientific Unions has endorsed the concept of an International GeosphereBiosphere Programe (IGBP) with its first objective focussed on Global Change. This objective is outlined in a volume of the same name edited by Malone and Roederer (1984). Malone wrote about the origin of the program and Roederer about the main thrust of the anticipated research. In particular, the latter stressed linkage between terrestrial climate systems and (a) the biosphere and (b) the sun. Whereas present-day meteorological systems are habitually seen as random, dynamic fluctuations about a steady-state system, Roederer emphasized the non-linearity nature of the interactions and evolution. He remarked specifically upon the 'subtle perturbations introduced by the variability of solar corpuscular and short-wavelength radiation'. The first symposium of this program was held in Ottawa, in September 1984. This served as a forum for 'state-of-the-art' reviews which serve as a spring-board for the new research directions. Somewhat earlier in the same year (May 1984) another interdisciplinary symposium had been called together in New York City, at Columbia University, ostensibly to celebrate the writer's 70th birthday. The 'Festschrift' volume entitled Climate Change (edited by Rampino et al., 1987) brings together a wide selection of papers that mainly concentrate on the events and processes of the last 10 ka. If for no other reason, the volume may be useful for a 66 page bibliography. For the inquiring reader, interested in the history and philosophy of science, it may be seen from the citations that most fundamental ideas were already postulated more than a century ago. 83
Many of these ideas have been set aside in the twentieth century preoccupation with data acquisition, an activity that has been facilitated by the development of practical electronics, the computer, and space vehicles, This thrust of human energy and funds, while dazzling in its conceptual impact, has not been without drawbacks. In a recent article about the vast proliferation of data processing, generating information without digestion, H.R. Pagels (executive director of the New York Academy of Sciences) remarked: Information tends to drive out knowledge. Information is just signs and numbers, while knowledge involves their m e a n i n g . . .
The geologists enjoy a luxury that is not generally shared by physicists and chemists. They enjoy historical perspective - - over four billion years of it. This perspective has generated a favorite aphorism: 'What has happened, can happen!' This knowledge should not lull us into a sense of false security, allowing us to say 'We've seen it all before'. Quite the contrary, 'Time's Arrow' flies forever forward. It never goes back. But it flies up the central axis of a spiral staircase, the steps of which are the graduations of geological time, the punctuations of evolutionary history as recognized by Eldredge and Gould (1972). Seen in mathematical terms, this historical spiral is a cyclic sequence. In connection with an international conference on the disposal of radioactive waste the writer was once asked to spell out the fundamental laws that the earth's history has to contribute to the world of science. After much cogitation, whittling and consultation, we came up with only four 'Earth Laws' each of which carries various axioms and corollaries (Fairbridge, 1980). These laws, in a nutshell, state: 1. Law of Finite Existence. Our galaxy, solar sytem,
84
R.W. Fairbridge
Major planetary conjunctions are also observable with the naked eye, e.g. Chinese references to 'five stars in a line appeared like polished jade beads', apparently in the year -916 (917 BC) when Mercury, Venus, Mars, Jupiter, and Saturn were in very close alignment (also Uranus and Neptune, but these would hardly count as 'bright stars'). The weakness of such time markers is their scatter (incompleteness) and their verbal basis (liable to mistranslation). Recent papers by Stuiver, Pearson, Becker and colleagues (1986) now provide a dendrochronologic annual record and an internationally confirmed data bank of terrestrial signals of the radiocarbon flux-rate variations that permit sun--earth correlations (Eddy, 1977) to an accuracy of +10 years, the sample-interval of 14C analyses. Episodes of sun history when emission and radiation values fluctuated wildly can now be correlated with the dynamic conditions set up by certain planetary alignments. Those configurations have now been chronologically determined for about 12 ka. Calibration of radiocarbon-dated geological and cultural materials can now be made with respect to certain epochs, with an accuracy of better than 50 years. At other times (due to strongly fluctuating 14C flux) precision deteriorates badly, and dates obtained for those time-intervals must be treated with caution (Schove, 1987). Nevertheless, the main trends of Ho|ocene climatically related events can now be set within a fixed astronomic framework. A joint project by Fairbridge and Shirley (1987) undertakes to prepare relevant computer software for economically available disks that can be employed for general scientific use. The various planetary time series and solar orbital calculations, as well as the radiocarA TEN-THOUSAND-YEAR CLIMATE bon flux record, can all be supplied on standard 13 cm Geologists,climatologists and archaeologists are find- (51/4 inch) or 8.75 cm (31/2 inch) 'floppy' diskettes. ing themselves increasingly in need of a precise chronological framework for establishing stratigraphic, paleoANNUAL TIME SERIES climatic, and cultural events during the present geoBesides the long dendrochonoiogical series, there are logical time-unit, the Holocene epoch. The writer, with the aid of many colleagues, has now established an several types of year-by-year records in nature that can astronomical foundation for this calendar, based on the be used as terrestrial proxies of climatic fluctuations. In NASA-JPL long ephemeris (DE-102) of Newhall et al. certain favored locations the width and density of the (1983) and cross-checked against the ephemeris formu- tree-ring wood can be correlated with the solar lae of the U.S. Naval Observatory and of the European periodicities (Sonett and Suess, 1983), but more standard (Meeus and Victor, 1983). Preliminary papers frequently, though with fluctuating intensity, with the have been published (Fairbridge and Sanders, 1987; 18.6 year lunar declination cycle (Currie, 1987; Currie Fairbridge and Shirley, 1987). Dynamic analyses have and Fairbridge, 1985). been made by Jose (1965). Continuously counted, annually layered ice cores To be useful in archaeological or geological dating, an display cycles of oxygen-isotope variability, reflecting astronomical calendar requires certain clearly identifi- water-temperature changes in the snow's evaporation able marker dates, apart from the annual periodicity source areas (Johnsen et al., 1972). Those cycles which is clearly established (outside of equatorial strikingly correspond to the principal periodicities of latitudes) by seasonal change, and length of day and the major planets. Klaus (1980) has shown that for night. Such dates are observable, as in the periodicities several centuries the decades of 'cold' oxygen isotopes of Venus which were employed in a sophisticated way exactly matched those marked by droughts in West by the Mayans of Mexico. Eclipses of sun and moon Africa, and other studies show a relationship to were widely observed in the past and can be used to precipitation patterns in northeastern North America. An approximately 20-year periodicity in both the latter establish certain dates, provided the location is known. sun, planets, earth and moon are all constrained in terms of mass, size and time. Energy is exchanged between them in terms of electromagnetic radiation, particle transfer and angular momentum. When the sun eventually burns up, several billion years in the future, life on earth will terminate (but not before). 2. Law of Physical Evolution. In its 4.6 billion-year history planet earth has progressively evolved, mainly in threshold steps, and in complex cycles, but never exactly repeating itself. Its organized record in rocks grows more complicated throug h time, while retaining innumerable vestiges of past events. 3. Law o f Biological Evolution. Since the first self-~ reproducing molecule appeared about 4 billion years ago, no interruption has ever occurred in a progressively branching and more complex biota. No major phylum ever became extinct. 4. Law of Equilibrium. During the 4 billion years the mean global temperature has remained at 18 + 5°C and the equatorial sea-surface temperature stays at 30 + I°C, while the climate is constantly changing in complex cycles (from 1 day to several million years) but always maintained by positive and negative feedback mechanisms. This 'credo' is virtually unknown either by the physicists or the man-in-the-street. It thus seems appropriate to use it as an introduction to this essay, which will attempt to bring out two themes: (a) the need for an accurate year-by-year chronology in order to establish our historical record of the last 10 ka in a precise framework; and (b) to point the way towards future research into the astronomical basis for such a chronology.
Quasi-Equilibrium in HoloceneClimaticChange and the Greenland ice cores (Mook and Hibler, 1976) seems seductively close to the 19.85 year SaturnJupiter Lap, a s~,nodic 'metronome' that is dubbed 'the Pulse of the Solar System' (Fairbridge and Sanders, 1987), although a linkage mechanism is not yet established. With additional data on West African droughts, the writer has been able to extend the Klaus correlation with the Greenland isotopic record by several more centuries. Another type of annual layering that displays climatic cycles of oxygen isotope variations is found in the seasonal banding of stalactite accretion, but no cave appears to carry a continuous record spanning the whole of the Holocene. Furthermore, this type of study is difficult to pursue because the integrity of the stalactites is usually jealously defended by the guardians of the various caves. After the tree rings, the most important annual layerings are those found in lacustrine varved clays. These are widespread in formerly glaciated regions, but require an enormous investment in time and money in boring the various lake basins and closely measuring the layer thickness. This investigation, begun nearly a century ago in Sweden by the Baron de Geer, has recently been rechecked and coordinated to the contemporary dates by Cato (1985). As climatic proxies the varves only reflect events within the limits of a particular basin, and then generally provide only an indication of the spring melt of the preceding winter's snow. Nevertheless, cycle analysis and correlations with tree-ring thicknesses carried out in Finland (Sirrn and Hari, 1971), show an approximate uniformity in northeast Scandinavia. The most important cycles are the luni-solar beat frequencies (such as the 93 year frequency). Marine varves are known, but only in certain favored areas. Normally, in well oxygenated basins, the bottom life will plough up the sediment of the sea floor ('bioturbation') in a way that tends to homogenize the signal. The result is usually a biogenic 'smoothing' over an interval of 1-3 ka, which is exactly in the zone of signals we are seeking to discover. In some favored basins, however, the bottom environment is anoxic and biologic scavengers are thus excluded. High latitude sites are contaminated and disturbed by 'ice rafting' (boulders and debris dropped from melting icebergs or sea ice). Intermediate latitudes marked by strong seasonality are ideal. Anoxic basins of this sort have been found off southern California and in the Gulf of California (Mexico). Calibration problems exist, but the work published so far is very promising (Pisias, 1978). COASTAL RADIOCARBON SAMPLES
A large number of studies have been made of coastal marine areas where a rich variety of different sediments can be subjected to various paleotemperature and other types of analysis, including radiocarbon dating. If the information needed is limited to a precision about +500 years there is little problem with the laboratory
85
'age'. The appraisal of the sample, its potential contamination, and the calibration to 'calendar' (sidereal or astronomical) years requires great care, however Literally thousands of dates are published that purport to represent the age of a high sea level in the range of 15-35 ka BP. Almost all of these, alas, reflect varying degrees of minor contamination, and there is today strong evidence that throughout that period the world sea level was in the range of 50-135 m below that of today. Neotectonics, including glacioisostatic crustal recovery, leads to widespread elevation anomalies but in the latitudes from which most of the samples are collected the implied rate of sustained vertical crustal motion (5-10 mm/year) would be distinctly unusual. Frequently in the same area there are also coastal formations of Eemian (Tyrrhenian) age, i.e. around 80-130 ka, that display little evidence of tectonic disturbance and are commonly quite horizontal over large distance at elevations in the range of 3-8 m above present MSL. If these late Pleistocene formations are not greatly displaced, then the younger, lac dated littoral facies cannot have suffered great vertical disturbances. It is quite illogical to claim Holocene crustal adjustments if Pleistocene rocks are undisturbed. As regards the materials sampled in these Holocene coastal assemblages, the most reliable are generally charcoals associated with coastal middens. They also provide an opportunity for controlling the midden shell dates. If the latter are of marine mollusca, there is always the possibility of their contamination by 'old water' brought to the surface by upwelling (particularly common in the Arctic, Peru and California). In such events the dates may be 300--600 years too old. Shells from the top of the midden may have been added over the centuries and correspondingly may give ages that are too young with respect to the shoreline. In barrier beach (beachridge) sequences, the shells and especially shell debris may be reworked from older beaches; where multiple dates are available in such cases, the youngest in any series is most likely to be correct. Driftwood samples in beach sequences are often too old, especially from the Arctic. Peat and wood samples (especially mangrove roots) from back-beach swamps and lagoons are likely to give reliable dates, except that care is needed to assess potential contamination by younger roots. Articulated shells from lagoons are clearly in growth positions and generally provide useful dates. When it comes to calibration, from radiocarbon years (often best indicated with Schove's convention 'year BP') to calendar years, reference should be made to the chronological diagrams in the papers by Stuiver and several others (in Radiocarbon, 28, 1986). It will be seen that in certain time spans the indicated date is likely to be accurate in the range of _ 10-20 years. At other times, due to protracted periods of strongly oscillatingl4C flux values, there may be an interval of 200 years or more when a wide range Of error (several centuries) must be expected. When attempting to reconstruct an astronomical chronology a large number
86
R.W. Fairbridge
of these dates should be set aside at first; after the chronological framework is built up from a very small number of closely screened (and hopefully 'accurate') dates, then the dates from the isotopically disturbed periods can be added to the record with the proviso that they are 'not incompatible' with the model presented. In no circumstances should dates of different samples be averaged; indeed, different molluscan species should not be mixed. A half-dozen 'good' dates are worth more than a hundred dubious ones. Sophisticated statistical procedures are often no better than computational electronic 'muscle-flexing'. MARINE STRATIGRAPHIC MODEL
Presented here is a very preliminary model of a Holocene chronology based upon three assumptions, or working hypotheses: (a) that major planetary fluctuating conjunctions determine episodes of low or strongly fluctuating solar emissions and radiation; (b) that these episodes are recorded on earth by high 14C flux interval.s as identified in tree-rings; and (c) that the incoming particulate solar energy is partly screened by the body of the moon and is modulated by the earth's magnetic field, short-time variations of which are believed to be caused by declination variables of the moon, the Chandler wobble and fluctuations in the terrestrial spin rate. Three extra-terrestrial forcing functions are thus envisaged, two from the sun and one relating to motions of the moon. The chronologies involved can be accurately calculated, but the amplitudes of the postulated effects can only be stated in generalized terms at the present juncture. The sun's electromagnetic radiation, in the optical and infrared wavelengths, is close to being constant, although a small variance through the ll-year sunspot cycle may be expected. In contrast a large variance through this same period is observed with respect to the extremely high UV spectrum. This is responsible for generating ozone in the stratosphere, where it is the principal 'greenhouse' agent, affecting the thermal conditions and the physical height of the stratopause in low latitudes. Ozone concentration, measured by rockets over the last 3 decades or so, shows a marked fluctuation with the sunspot cycle, but during the last solar minimum it appears to have fallen appreciably more than expected, due to anthropogenic pollution. Nevertheless, from observations in the high Alps at Arosa (Switzerland), in spite of large fluctuation, there is no overall change (e.g. Diitseh, 1979). As concerns the partiele radiation (maximum during solar flares), high-latitude disturbances to the general circulation are triggered (Bucha, 1984). Both flares and the earth's spin and Chandler wobble relate to planetary dynamics, notably the Jupiter--earth-Venus alignments, every 5.55 years. ENHANCEMENT YEARS AND ACTIVITY SPIKES Most of the proxy climatic series mentioned earlier
disclose a condition approaching that of a steady state. Departure from that mean is engendered by varied agencies, the astronomically based ones being predictable (see Table 1)0 The principal disturbing processes include: (1) Catastrophic type events, such as volcanic eruptions that generate dust veils and aerosols (each one differing from the last in terms of dimensions, material, latitude, season and so on) and, although expectable, they are-hardly predictable in an exact chronological sense. Another catastrophic type of disturbance is the threshold-type outbreak of flooding due to glacierdam withdrawal or tilting. (2) Lunar and luni-solar tidal effects, both atmospheric and oceanic, are reasonably predictable. Due to crustal loading (by tidal, shelf waters), as well as earth tides, some earthquakes and volcanic eruptions are also affected by these influences. Through tidally influenced ocean-current variations, sea-surface temperatures (SSTs) are sometimes subject to quite large changes; the associated steric (thermal, water-volume) effect is demonstrated by tide gauges. (3) The spin axis of the earth undergoes a wellknown 1.2 year nutation, known as the Chandler Wobble. As noted by Currie and Fairbridge (1985) a beat frequency of 6.2 years develops that is recorded in almost all climatic proxies. Furthermore, there are frequent short-term changes of spin rate, some of which are clearly related to climate and some to the solar wind or other exogenetic agencies. Long-term ('secular') change in the earth's axial orientation, affecting the seasons and thus the entire global climate, is related to the precession of the perihelion (20,969 years). This periodicity is an exact multiple of the various shortterm astronomic variables (e.g. 16 x 19.859 years Saturn-Jupiter Lap; 66 x 317.7 year Solar Angular Velocity Cycle; 1112 x 18.613 year Lunar Nodal Cycle). (4) Short-term or abrupt departures tend to be spread out or delayed by multiple oceanographic and glacial lag factors and enhanced or retarded by dynamic feedback mechanisms. As the mean oceanic turnover time is of the order of 500 years or more, some of the latitudinal heat exchanges on the globe tend to exceed in length many of the cyclic changes that initiate them. (5) Until recently the concept of a cyclic variance of solar radiation was opposed by the 'establishment', and so far only the present solar cycle values have been measured beyond any reasonable doubt. Nevertheless, it may now be assumed that such variance must also have been true for earlier cycles, and in varying degrees, depending upon a range of potential indicators. In the historical era, documentary evidence of auroras is generally accepted as persuasive. For the Holocene in general the radiocarbon flux rate obtained from dendrochronological series seems to be a reasonably consistent indicator of solar activity. In the course of each solar cycle the interaction between the solar wind and the earth's magnetic field modulates the galactic cosmic ray flux in such a way that the high solar
87
Quasi-Equilibrium in Holocene Climatic Change TABLE 1. Holocene astrophysical chronology {1)
C-14 FLUX MAX.
=low SOL act) [¢10 yr]
MIN, (=high sol. act.) [-+10 yr]
(2) PLANETARY
SOLAR FACTORS
Major Conjunctions 317,7 yr 45.37 etc
Saturn-Jupiter Lunar C. 997.8 yr
(3)
LUNAR TIDAL
(8) 111 yr,
ANO
LUN I-SOLAR FACTORS
(b) 18.6 yr.
(c) 16.03 yr
1615
1749 1623
(4)
Marine Stratigraphy Riae - Fall
TERRESTRIAL PROXIES
C - 14
Pollen Zones "Ages" B.P
A.D 2 kyr
1 ky
1751
1761 1626 1530
1630
1624
1370
1442 1306"
1452
1306
1125
1155
8O9
857
990 900 807
1447
1443 1298 1154 1118
<
) •
<
1
SA-2 < )
865 812
-1100 ±150
685 560
560
555 498
563 491
3
34 -4 -143
256 166 36 -17 -144
491
430
)
390 261
260 173 30
AD -143 -250
173 35 -6 -140
-35
SA-1
-2100
-210 -334
-342 -468
-462 -550 -600 -780
-642 -778
-632
-916" -1096
-646
-649 -744
-929
-926
-918 -1098
-1227
-1242
-1242
-774
-870 1 kyl
-960 -1095
> SB-2
-1170 -1370 -1416 -1662
-1670 -1790
-1733
-2010 -2120 *2260
-1735
-1728 -1918
-2052
-2054 -2124 -2178 -2358 -2412 -2557
-1823
-1850 -2 kyl
-1422 -1530
-1525
-1530
-2150
-2050 -2187
-2121
-2366 -2450 -2550
-2419 -2510
-2554
-2716
-2790
-2719 -2864
-2865
-2850 - 3ky
-2560
-2548
-3010
-3050
-3003 -3131
-3015
-3280 -3320
-3390
-3321"
-3312
-3328
-3002
-3009 -3136
-3316
-3316
-3610
-3602
-3908
-3819 -3910
-3818 -3940 -4050
- 4 kyr -4280
-4136
-4135 -4274
-4206
-4454 -4591
-4504
-4350 -4450 -4600
-4630
-4930
-4950
-4452
-4127 -4213 -4269 -4409 -4593 -4819
- 5kyl
-4863 -4953 -5090
-4802
.9. -----~
SB-1
> -5200
>
AT-2
-4806 -4901
-5100
-5190 -5230 -5360
~3800
-5104
-5103
-5100
-5698
-5695 -5730 -5857
-5397 6600 :250
-5405 -5695 -5720 -5900
- 6 kyr
-5950
-5728 -5863 -5993
-5993
AT-1
-6001
NOTES: " -NUSJ Lap (2222 yr - 49 x 45.37 - 7 x 317; 24505 y r . 53 x 45.37) Period 317.7 - 7 x 45.37 (HudSon Bay ato~0~sa cy~e) Period 297 8 - 6.2 (Chandler Wobt~4 beet: 9enmal climate t i t l e ) Period 111 = { Luni-Sotgr - Pehhelion Tide). 9g x 1132 - 20 • S,5S (JEV Lap)
Column 1. High and low peaks of radiocarbon flux in tree rings (Stuiver and others, 1986). Samples generally reflect a precision of _+ 5-10 years. Actualistic significance is suggested by the peak episodes (low solar radiation and weak geomagnetic field) corresponding to El Nifio years, by catastrophic droughts in the Sahel andby monsoon failure in India. In mid-latitudes the solar weakness is reflected by abrupt and extreme climatic fluctuations (higher and lower than normal; tree rings alternatively very wide and very narrow). Column 2. Planetary-solar cycle correlations. Although the variance of most of the planetary cycles is less than _+ 1 year, most of the synodic (lap) rates of the major planets are greater than 10 years and tend to alternate in length, so that exact coincidences are not expected. The longitudinal shift of the outermost planets is only a few degrees a year. Column 3. Principal lunar periodicities (see Table 2 for typical phase relationships and correlations with the planetary-solar periods). Column 4. General transgressive or regressive trends in marine coastal stratigraphy. Transgressions are marked by superposition over paleosols, fluvial or lagoonal sediments; regressions generally by deltaic progradation, often associated with widespread (slightly diachronons, peat layers. This stratigraphy is best preserved in tectonicaily negative, subsiding situations. In uplift areas, the evidence is generally limited to beach ridges. Pollen zones are designated SA (sub-Atlantic), SB (sub-Boreal), and AT (Atlantic).
88
R . W . Fairbridge
activity phase is reflected by low radiocarbon production. Tree-ring growth widths, in favored living areas, are now found to vary in phase with the sun's activity cycles, showing that climate is directly modified by those variations. From the above summary, it is clear that certain days, months, years, or decades are characterized by particular events, 'spikes', or fluctuations, and from study of appropriate astronomical data those events are
predictable. Such predictions can be tested against the historical and geological records. Table 2 illustrates how certain epochs are characterized by clusters of planetary, solar and lunar events. They may be called 'enhancement years' which recognize that solar and terrestrial stresses are brought to bear, enhancing the usual reactions. It should be emphasized that these studies are still in their infancy, and at the present juncture, the author's role is merely exploratory.
T A B L E 2. E n h a n c e m e n t years A D 835-2001, integrating solar and lunar periodicities
A-1 SUNSPOT MAX.
A-2 CYCLE MIN.
[2001] 1987 1969 1913 1894 1856 1838 1784 1727 1689 1650 1633 1615 1578 1558 1466 1450 1430 1411 1392 1356 "1340" 1318 1297 1281 1261 "1246" "1227" "1 209" 1168 1149 1111 1093 "1 036" 1003 981 962 946 925 910 872 851 835
B-1 B-2 LUNAR CYCLES Nodal Aplldes 18.6 y r . 8.647 yr.
B-3 Chandler 6.2
yr.
2006.5 1987.8 1969.2 1913.4 1894.8 1857.6 .1838.9 1783.1 1727.3 1690.0 1652.8 1634.2 1615.6 1578.4 1559.7 1466.7 1448.0 1429.4
2005.3 1987.6 1969.9 1916.8 1890.2 1854.9 1837.2 1784.0 1730.9 1686.7 1651.4 1633.7 1615.9 1580.6 1582.9 1465.6 1447.9 1430.2
2004.9 1986.4 1967.7 1911.9 1893.3 1856.1 1837.5 1781.7 1725.8 1688.6 1651.4 1632.8 1614.2 1576.9 1558.3 1465.3 1446.7 1428.1
1410.8 1392.2 1354.9 1336.4 1317.7 1299.1 1280.5 1261.9 1243.3 1224.7 1206.1 1188.9 1150.3 1113.0 1094.4 1038.5 1001.4 982.7 964.1 945.5 926.9 908.3 871.1 852.4 833.8
1412.5 1394.8 1359.4 1341.7 1315.2 1297.5 1279.8 1262.1 1244.4 1226.7 1209.0 1164.8 1147.1 1111.7 1093.9 1032.1 1005.5 978.9 961.8 943.6 925.9 908.2 872.8 855.1 837.4
1409.5 1390.9 1359.9 1335.1 1316.5 1297.9 1279.3 1260.7 1242.1 1223.5 1204.9 1167.7 1149.1 1111.9 1093.3 1037.5 1000.3 981.7 963.1 944.5 925.9 907.3 870.1 851.5 832.9
C1, 83
2, 3, 4, 5 PLANETARY- SOLAR 93 111 178 297
-1-
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--I-
•
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6-
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D
...............
i
LUNI-SOLAR GABRIEL CYCLE 744.5 y r
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N o te : " d a t e s uncertain; square brackets-phase reversal
Explanation: Selected years (mostly at _+ ! year precision) are presented here to illustrate the m a n y ways in which a particular interval in the astronomic chronology m a y be subject to multiple influences. A modest stress is thus liable to accumulate by successive feedbacks and e n h a n c e m e n t processes; these stresses are applied to the sun by the planets (86% of their angular m o m e n t u m is clue to Jupiter and Saturn), and by the sun and m o o n to the earth. In columns A-1 and 2 (sunspot maxima and minima) the precision drops off for years earlier than the 15th century, and dubious dates are indicated by parentheses. In c o l u m n s B-1-3 (lunar cycles) the nodal a n d apsides values are very regular, but the Chandler wobble beat frequency (6.4 years; 3 x 6.2 = 18.6) has an intercycle variance of _+ 1 year. in c o l u m n s C-1-6 all the periods are ultimately commensurable: e.g. 83.3 years (heliomagnetic a n d flare cycle = 7 x 11.86, 15 x J E V lap; 2 x 83.3 = 9 x 18.6 - 1112 years - 56 SJL -- 24.5 U S L = 87 N J L = 200 J E V L ) ; 93 years (perigee-syzygy-perihelion cycle b 5 x 18.6 = 10.5 x 8.847 = 15 x 6.2 = 3.31); 111 years (extreme PSP cycle = 20 x 5.55, J E V L = 10 x 11.1 sunspot cycle = 100 x 1.1 lunar tide); 178.71 years (sun's orbital s y m m e t r y progression a n d 'All Planet Synod' ,= 9 x 19.859 S.IL = 9.6 x 18.61); three examples of 297.2 year (luni-solar-Jupiter-Saturn beat: 18.61/19.859; 297.85 -- 16 x 19.859 = 17 x 18.61); two examples of 317.71 years ( m e a n U r a n u s - S a t u r n - J u p i t e r Lap; s u n ' s angular velocity max./min./period -- 7 x 45.37 U S L = 16 x 19.859 S,IL). C o l u m n D - - illustrates examples of the luni-solar combination of the "All C o m p o n e n t ' Gabriel Cycle of 744.5 years (40 x 18.6, 8 x 93; 18 x 744.5 -- 13.403 = 75 x 187.7 = 45 x 297.85 = 5 x 2680.7, the ' J u p i t e r - S a t u r n R e s o n a n c e Drift').
Quasi-Equilibrium in Holocene Climatic Change
89
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