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A Chaotic Holocene Climate?

Posted on: June 11, 2019

 

FIGURE 1: THE YOUNGER DRYAS EVENT IN THE HOLOCENE

youngerDryas

FIGURE 2: THE BRONZE AGE WARMING EVENT IN THE HOLOCENE

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FIGURE 3: THE LAST GLACIATION: EEMIAN TO HOLOCENE

 

 

FIGURE 4: FRAMES 11 KYBP APART FROM 120 TO 66 KYBP

        120, 109, 99, 88, 77, 66 KYBP

 

FIGURE 5: FRAMES 11 KYBP APART FROM 56 TO 0 KYBP

56, 45, 34, 23, 13, 0 KYBP

 

 

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HOLOCENE CLIMATE HISTORY FROM 15000YBP

  1. Figure 3 above is a video that shows a section of the Northern Hemisphere that contains the location where the Laurentide ice sheet forms during glaciation cycles.  It is an animation of the most recent glaciation sequence from the previous interglacial (the Eemian), through the Last Glaciation Period (LGP), to the present interglacial (the Holocene). It begins in the Eemian interglacial ≈120,000 years before the present (120KYBP) relatively free of ice except for Greenland and moves forward at 1,791 years per second to the present; thus beginning and ending in almost identical iceless states except for Greenland. In between these iceless interglacial states is seen the growth and decay of the last glaciation. These changes are violent, non-linear, and chaotic. As seen in the video, both the growth in glaciation from 120KYBP to about 56KYBP and its decay back to interglacial conditions contain multiple cycles of growth and decay at centennial and millennial time scales. The timing of these changes may be difficult to see in the video because of its extremely fast progression at ≈2000 years per second. It is made somewhat clearer in Figures 4&5 that appear immediately below Figure 3.
  2. Figure 4 and Figure 5 show the glaciation condition in still frames that are approximately ≈11,000 years apart. Figure 4 shows conditions in the first half of the time span at 120, 109, 99, 88, 77, and 66 KYBP. Here we see a growth of glaciation from the Eemian interglacial condition that progresses in cycles of growth and retreat in glaciation. The reason ice accumulates during glaciation is that growth events overcome retreat events. In this chaotic way, glaciation reaches a maximum The Last Glacial Maximum (LGM) in the first frame of Figure 5.
  3. Figure 5 shows conditions for the second time span at 56, 45, 34, 23, 13, 0 KYBP. These frames show glacial retreat after its maximum extent at 56KYBP. As in the growth phase, glacial retreat also progresses in cycles of growth and retreat in a violent and chaotic way, but in this phase of the glaciation cycle retreat events overcome growth events and glaciation ice sheets gradually dissipate until an interglacial period such as the the Holocene interglacial is fully established in the last frame of Figure 5 at 0KYBP. Thus approximately half of the Last Glacial Period (LGP) shows glacial growth and the other half shows glacial retreat. It is important to note that although the chaotic volatility in the glaciation cycle appears rapid and violent in the video, these changes occur at millennial and longer time scales and the video moves forward at ≈2000 years per second.
  4. In the Quaternary Ice Age in which we live, the earth is mostly in a glaciation state exhibiting glacial growth in the earlier portion and glacial retreat in the latter portion. In between glaciation periods are brief interglacials lasting approximately 10% of the time span of glaciation periods. Glaciations last about ≈100,000 years give or take a few thousand and interglacials about ≈10,000  years give or take a few thousand. We are currently in the Holocene interglacial. The previous interglacial is called the Eemian.
  5. The Eemian interglacial is described in a related post [LINK] where we see that the chaotic back and forth cyclical progress of the glaciation phase is also seen in the interglacial phase. Thus, in the Eemian interglacial we find a similarly violent state of cyclical climate oscillating between cold and hot periods as well as between rising and falling sea levels. Thus the cyclical and violent changes of warming and and cooling seen in glaciation periods are also found in interglacials. In the Eemian, and in interglacials in general, these  changes within  occur at multi-decadal, centennial and millennial time scales. The bibliography presented below shows that similar, though less intense, cycles of cooling and warming are also found in the Holocene from its violent inception in the Younger Dryas event  to the present.
  6. The Younger Dryas Event (YDE) is described in a related post [LINK] .The paleo data collected by Willi Dansgaard and others show that as soon as the Last Glacial Period had apparently ended, a series of brief but violent cycles of glaciation and deglaciation conditions at very short time scales intervened. Figure 1 (reproduced below) is a graphical depiction of the violent and chaotic temperature changes seen in the YDE. Here red lines indicate warming, blue lines indicate cooling, and black lines are neutral. At ≈14,450YBP, we see a steep vertical red line as that appears to be an initial stage of the end of the LGP and the onset of the Holocene. Instead, at≈14,500YBP, rapid cooling and glaciation returned and drove temperatures in Greenland down by 15C at ≈12,000YBP. Shortly thereafter, ≈11,700YBP, a strong warming trend set in and persisted with a steady warming of ≈17C that rescued the Holocene from the YDE but two more glacial interruptions were still to come.
  7. The first of these two cooling events is called the 8.2K cooling (shown in blue) because it ends 8200YBP. The Holocene interglacial recovered from the 8.2K mini glacial event and warmed to the so called “Holocene Climate Optimum” (HCO) ≈7000YBP. The HCO, described in a related post [LINK] , is credited with the Neolithic Revolution that is thought to have created human civilization. It brought hunter gatherer humans out of the forests and caves and into a settled agricultural economy with farms and permanent homes eventually leading to kingdoms, nations, learning, and innovation described in a related post on the Bronze Age [LINK] . The black curve that runs from ≈7000YBP to the present is the temperature history of the Holocene since the warming began in earnest in the HCO.
  8. Four other Holocene temperature events since, in addition to the HCO, are considered important in the climate history of the Holocene interglacial. These are the Bronze Age warm period ≈3000YBP, (also called the Minoan Warm Period (BAWP), the Roman warm period (RWP)≈2000YBP, the Medieval warm period (MWP) ≈1100YBP, and the Little Ice Age (LIA) ≈500YBP-100YBP (the last blue cooling line in the chart). The current warm period, described as Anthropogenic Global Warming (AGW) caused by the Industrial Economy although some research implies that it may be a natural recovery from the LIA as described in a related post [LINK] . Posts on the MWP [LINK] and the LIA [LINK] are also relevant in this context.
  9. Thus we find that both glaciation and interglacial periods exhibit millennial scale chaotic behavior. In the bibliography below Gerard Bond, in “A pervasive millennial-scale cycle in North Atlantic Holocene and glacial climates.” science278.5341 (1997), writes that “pacings of the Holocene events and of and those in the last glaciation are statistically the same. Together, they make up a series of climate shifts with a period close to 1470 ± 500 years“. That is, although glaciation and interglacials are entirely different states of the earth’s surface climate system, both are subject to the same underlying chaotic volatility at the same time scale.
  10. A shorter time scale is implied in Wanner, Heinz “Structure and origin of Holocene cold events.” Quaternary Science Reviews 30.21-22 (2011). The paper describes the Holocene as an interglacial with an overall warming trend that is repeatedly interrupted by cold events at centennial and shorter time scales. He identifies the six cold events as (8200, 6300, 4700, 2700, 1550 and 550YBP). Mayeweski 2004 also identifies six cold events but dates them as 9000″8000, 6000-5000YBP, 4200-3800YBP, 3500-2500YBP, 1200-1000YBP, and 600-150YBP.
  11. However, as noted by many authors in the bibliography below, the Holocene is also marked by episodes of exceptional warmth. Other than the initial HCO, the most notable of these events are (1) the Bronze Age Warming (BAW) also known as the Minoan Warm Period ≈3000YBP, The Roman Warm Period (RWP) ≈2000YBP, the Medieval Warm Period (MWP) ≈1000YBP, and the current warm period thought to be artificial and a creation of the industrial economy. The millennial time scale is evident in these events that include the current warm period.
  12. SUMMARY & CONCLUSION: Climate appears to exhibit properties of non-linear dynamics and deterministic chaos over a large range of time scales. Glaciation is not a linear and well behaved period of cooling and ice accumulation and deglaciation is not a linear and well behaved period of warming and ice dissipation. Rather, both glaciation and deglaciation are chaotic events consisting of both processes differentiated only by a slight advantage to ice accumulation in glaciation and a slight advantage to ice dissipation in interglacials. In this context, the Holocene must be studied and understood as a chaotic system with multiple episodes of warming and ice dissipation and multiple episodes of cooling and ice accumulation. Viewed in this way, the current warming trend, when compared with the HCO, BAW, RWP, MWP, and in the context of alternating mini glaciations, can be understood as a natural recovery from the Little Ice Age [LINK] . The Industrial Revolution falls conveniently in the middle and it is tempting to see it as causal in the context of the study of human impacts on nature. However, it is just as credible if not more so to describe it as coincidental rather than causal when seen in the context of the warming and cooling dynamics of the Holocene. With regard to the principle of Occam’s razor, the simpler explanation in terms Holocene dynamics is superior to the the complicated AGW explanation particularly so in terms of the many vexing issues in AGW that have not been resolved and that may never be resolved [LINK] . 

 

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HOLOCENE BIBLIOGRAPHY

 

  1. georgeDentonDenton, George H., and Wibjörn Karlén. “Holocene climatic variations—their pattern and possible cause.” Quaternary Research 3.2 (1973): 155-205. In the northeastern St. Elias Mountains in southern Yukon Territory and Alaska, C14-dated fluctuations of 14 glacier termini show two major intervals of Holocene glacier expansion, the older dating from 3300-2400 calendar yr BP and the younger corresponding to the Little Ice Age of the last several centuries. Both were about equivalent in magnitude. In addition, a less-extensive and short-lived advance occurred about 1250-1050 calendar yr BP (A.D. 700–900). Conversely, glacier recession, commonly accompanied by rise in altitude of spruce tree line, occurred 5975–6175, 4030-3300, 2400-1250, and 1050-460 calendar yr BP, and from A.D. 1920 to the present. Examination of worldwide Holocene glacier fluctuations reinforces this scheme and points to a third major interval of glacier advances about 5800-4900 calendar yrs BP; this interval generally was less intense than the two younger major intervals. Finally, detailed mapping and dating of Holocene moraines fronting 40 glaciers in the Kebnekaise and Sarek Mountains in Swedish Lapland reveals again that the Holocene was punctuated by repeated intervals of glacier expansion that correspond to those found in the St. Elias Mountains and elsewhere. The two youngest intervals, which occurred during the Little Ice Age and again about 2300–3000 calendar yrs BP, were approximately equal in intensity. Advances of the two older intervals, which occurred approximately 5000 and 8000 calendar yr BP, were generally less extensive. Minor glacier fluctuations were superimposed on all four broad expansion intervals; glacial expansions of the Little Ice Age culminated about A.D. 1500–1640, 1710, 1780, 1850, 1890, and 1916. In the mountains of Swedish Lapland, Holocene mean summer temperature rarely, if ever, was lower than 1°C below the 1931–1960 summer mean. Summer temperatures varied by less than 3.5°C over the last two broad intervals of Holocene glacial expansion and contraction. Viewed as a whole, therefore, the Holocene experienced alternating intervals of glacier expansion and contraction that probably were superimposed on the broad climatic trends recognized in pollen profiles and deep-sea cores. Expansion intervals lasted up to 900 yr and contraction intervals up to 1750 yr. Dates of glacial maxima indicate that the major Holocene intervals of expansion peaked at about 200–330, 2800, and 5300 calendar yr BP, suggesting a recurrence of major glacier activity about each 2500 yr. If projected further into the past, this Holocene pattern predicts that alternating glacier expansion-contraction intervals should have been superimposed on the Late-Wisconsin glaciation, with glacier readvances peaking about 7800, 10,300, 12,800, and 15,300 calendar yr BP. These major readvances should have been separated by intervals of general recession, some of which might have been punctuated by short-lived advances. Furthermore, the time scales of Holocene events and their Late-Wisconsin analogues should be comparable. Considering possible errors in C14 dating, this extended Holocene scheme agrees reasonably well with the chronology and magnitude of such Late-Wisconsin events as the Cochrane-Cockburn readvance (8000–8200 C14 yr BP), the Pre-Boreal interstadial, the Fennoscandian readvances during the Younger Dryas stadial (10,850-10,050 varve yr BP), the Alleröd interstadial (11,800-10,900 C14 yr BP), the Port Huron readvance (12,700–13,000 C14 yr BP), the Cary/Port Huron interstadial (centered about 13,300 C14 yr BP), and the Cary stadial (14,000–15,000 C14 yr BP). Moreover, comparison of presumed analogues such as the Little Ice Age and the Younger Dryas, or the Alleröd and the Roman Empire-Middle Ages warm interval, show marked similarities. These results suggest that a recurring pattern of minor climatic variations, with a dominant overprint of cold intervals peaking about each 2500 yr, was superimposed on long-term Holocene and Late-Wisconsin climatic trends. Should this pattern continue to repeat itself, the Little Ice Age will be succeeded within the next few centuries by a long interval of milder climates similar to those of the Roman Empire and Middle Ages. Short-term atmospheric C14 variations measured from tree rings correlate closely with Holocene glacier and tree-line fluctuations during the last 7000 yr. Such a correspondence, firstly, suggests that the record of short-term C14 variations may be an empirical indicator of paleoclimates and, secondly, points to a possible cause of Holocene climatic variations. The most prominent explanation of short-term C14 variations involves modulation of the galactic cosmic-ray flux by varying solar corpuscular activity. If this explanation proves valid and if the solar constant can be shown to vary with corpuscular output, it would suggest that Holocene glacier and climatic fluctuations, because of their close correlation with short-term C14 variations, were caused by varying solar activity. By extension, this would imply a similar cause for Late-Wisconsin climatic fluctuations such as the Alleröd and Younger Dryas.
  2. Hammer, Claus U., Henrik B. Clausen, and Willi Dansgaard. “Greenland ice sheet evidence of post-glacial volcanism and its climatic impact.” Nature 288.5788 (1980): 230. Acidity profiles along well dated Greenland ice cores reveal large volcanic eruptions in the Northern Hemisphere during the past 10,000 yr. Comparison with a temperature index shows that clustered eruptions have a considerable cooling effect on climate, which further complicates climatic predictions.
  3. O’Brien, S. R., (Mayewski). “Complexity of Holocene climate as reconstructed from a Greenland ice core.” Science 270.5244 (1995): 1962-1964.  Glaciochemical time series developed from Summit, Greenland, indicate that the chemical composition of the atmosphere was dynamic during the Holocene epoch. Concentrations of sea salt and terrestrial dusts increased in Summit snow during the periods 0 to 600, 2400 to 3100, 5000 to 6100, 7800 to 8800, and more than 11,300 years ago. The most recent increase, and also the most abrupt, coincides with the Little Ice Age. These changes imply that either the north polar vortex expanded or the meridional air flow intensified during these periods, and that temperatures in the mid to high northern latitudes were potentially the coldest since the Younger Dryas event.
  4. Angelakis, Andreas N., and Stylianos V. Spyridakis. “The status of water resources in Minoan times: A preliminary study.” Diachronic Climatic Impacts on Water Resources. Springer, Berlin, Heidelberg, 1996. 161-191.A well-known passage in Homer’s Odyssey, probably based on an ancient ritual myth, tells the story of Demeter, the Greek corn-goddess and Iasion, the son of Zeus by Electra, daughter of Atlas. The latter was the guardian of the pillars of heaven (Odyssey, 1.53), the Titan who holds the sky up (Hesiod, Theogony, 517) and is, thereby, identified with water and rainfall. [FULL TEXT DOWNLOAD .
  5. Alley, Richard B., (Mayewski)  “Holocene climatic instability: A prominent, widespread event 8200 yr ago.” Geology 25.6 (1997): 483-486.  The most prominent Holocene climatic event in Greenland ice-core proxies, with approximately half the amplitude of the Younger Dryas, occurred ∼8000 to 8400 yr ago. This Holocene event affected regions well beyond the North Atlantic basin, as shown by synchronous increases in windblown chemical indicators together with a significant decrease in methane. Widespread proxy records from the tropics to the north polar regions show a short-lived cool, dry, or windy event of similar age. The spatial pattern of terrestrial and marine changes is similar to that of the Younger Dryas event, suggesting a role for North Atlantic thermohaline circulation. Possible forcings identified thus far for this Holocene event are small, consistent with recent model results indicating high sensitivity and strong linkages in the climatic system.
  6. Bond, Gerard, et al. “A pervasive millennial-scale cycle in North Atlantic Holocene and glacial climates.” science278.5341 (1997): 1257-1266.  Evidence from North Atlantic deep sea cores reveals that abrupt shifts punctuated what is conventionally thought to have been a relatively stable Holocene climate. During each of these episodes, cool, ice-bearing waters from north of Iceland were advected as far south as the latitude of Britain. At about the same times, the atmospheric circulation above Greenland changed abruptly. Pacings of the Holocene events and of abrupt climate shifts during the last glaciation are statistically the same; together, they make up a series of climate shifts with a cyclicity close to 1470 ± 500 years. The Holocene events, therefore, appear to be the most recent manifestation of a pervasive millennial-scale climate cycle operating independently of the glacial-interglacial climate state. Amplification of the cycle during the last glaciation may have been linked to the North Atlantic’s thermohaline circulation.
  7. Roberts, Neil, et al. “The age and causes of Mid-Late Holocene environmental change in southwest Turkey.” Third Millennium BC climate change and old world collapse. Springer, Berlin, Heidelberg, 1997. 409-429.  Proxy records such as lake sediment sequences provide important data on abrupt environmental changes in the past, but establishing their specific causes from the palaeoenvironmental record can be problematic. Pollen diagrams from southwest Turkey show a mid-late Holocene pollen assemblage zone, designated as the Beyşehir Occupation phase, the onset of which has been 14C dated to ca. 3000 BP (ca. 1250 BC). A second millennium BC date for the start of the Beyşehir Occupation phase can now be confirmed as a result of the discovery of volcanic tephra from the Minoan eruption of Santorini (Thera) in lake sediment cores from the region. Palaeoecological analyses on sediment cores from Gölhisar gölü, a shallow montane lake, indicate that tephra deposition was followed by a sustained response in the aquatic ecosystem, in the form of increased algal productivity. The onset of pollen changes marking the beginning of the Beyşehir Occupation phase was not, on the other hand, precisely coincident with the tephra layer, but rather occurred at least a century later at this site. Despite the paucity of archaeological evidence for Late Bronze Age settlement in the Oro-Mediterranean region of southwest Turkey, it would appear that the second millennium BC saw the start of a period of major human impact on the landscape which continued until the late first millennium AD. The Santorini ash represents an important time-synchronous, stratigraphic marker horizon, but does not appear to have been the immediate cause of the onset of the Beyş ehir Occupation phase.
  8. Bond, Gerard, et al. “Persistent solar influence on North Atlantic climate during the Holocene.” science 294.5549 (2001): 2130-2136.  Surface winds and surface ocean hydrography in the subpolar North Atlantic appear to have been influenced by variations in solar output through the entire Holocene. The evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon-14 and beryllium-10 and centennial to millennial time scale changes in proxies of drift ice measured in deep-sea sediment cores. A solar forcing mechanism therefore may underlie at least the Holocene segment of the North Atlantic’s “1500-year” cycle. The surface hydrographic changes may have affected production of North Atlantic Deep Water, potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally.
  9. Stenni, Barbara, et al. “Eight centuries of volcanic signal and climate change at Talos Dome (East Antarctica).” Journal of Geophysical Research: Atmospheres 107.D9 (2002): ACL-3.  During the 1996 Programma Nazionale di Ricerche in Antartide‐International Trans‐Antarctic Scientific Expedition traverse, two firn cores were retrieved from the Talos Dome area (East Antarctica) at elevations of 2316 m (TD, 89 m long) and 2246 m (ST556, 19 m long). Cores were dated by using seasonal variations in non‐sea‐salt (nss) SO42− concentrations coupled with the recognition of tritium marker level (1965–1966) and nss SO42− spikes due to the most important volcanic events in the past (Pinatubo 1991, Agung 1963, Krakatoa 1883, Tambora 1815, Kuwae 1452, Unknown 1259). The number of annual layers recognized in the TD and ST556 cores was 779 and 97, respectively. The δD record obtained from the TD core has been compared with other East Antarctic isotope ice core records (Dome C EPICA, South Pole, Taylor Dome). These records suggest cooler climate conditions between the middle of 16th and the beginning of 19th centuries, which might be related to the Little Ice Age (LIA) cold period. Because of the high degree of geographical variability, the strongest LIA cooling was not temporally synchronous over East Antarctica, and the analyzed records do not provide a coherent picture for East Antarctica. The accumulation rate record presented for the TD core shows a decrease during part of the LIA followed by an increment of about 11% in accumulation during the 20th century. At the ST556 site, the accumulation rate observed during the 20th century was quite stable.
  10. Mayewski, Paul A. (aka Ice Man). “Holocene climate variability.” Quaternary PaulMayewskiresearch 62.3 (2004): 243-255. Although the dramatic climate disruptions of the last glacial period have received considerable attention, relatively little has been directed toward climate variability in the Holocene (11,500 cal yr B.P. to the present). Examination of 50 globally distributed paleoclimate records reveals as many as six periods of significant rapid climate change during the time periods 9000″8000, 6000″5000, 4200″3800, 3500″2500, 1200″1000, and 600″150 cal yr B.P. Most of the climate change events in these globally distributed records are characterized by polar cooling, tropical aridity, and major atmospheric circulation changes, although in the most recent interval (600″150 cal yr B.P.), polar cooling was accompanied by increased moisture in some parts of the tropics. Several intervals coincide with major disruptions of civilization, illustrating the human significance of Holocene climate variability.
  11. Magny, Michel. “Holocene climate variability as reflected by mid-European lake-level fluctuations and its probable impact on prehistoric human settlements.” Quaternary international113.1 (2004): 65-79.  A data set of 180 radiocarbon, tree-ring and archaeological dates obtained from sediment sequences of 26 lakes in the Jura mountains, the northern French Pre-Alps and the Swiss Plateau was used to construct a Holocene mid-European lake-level record. The dates do not indicate a random distribution over the Holocene, but form clusters suggesting an alternation of lower and higher, climatically driven lake-level phases. They provide evidence of a rather unstable Holocene climate punctuated by 15 phases of higher lake-level: 11 250–11 050, 10 300–10 000, 9550–9150, 8300–8050, 7550–7250, 6350–5900, 5650–5200, 4850–4800, 4150–3950, 3500–3100, 2750–2350, 1800–1700, 1300–1100, 750–650 cal. BP and after 1394 AD. A comparison of this mid-European lake-level record with the GISP2-Polar Circulation Index (PCI) record, the North Atlantic ice-rafting debris (IRD) events and the 14C record suggests teleconnections in a complex cryosphere-ocean-atmosphere system. Correlations between the GISP2-PCI, the mid-European lake-level, the North Atlantic IRD, and the residual 14C records, suggest that changes in the solar activity played a major role in Holocene climate oscillations over the North Atlantic area.
  12. Alley, Richard B., and Anna Maria Ágústsdóttir. “The 8k event: cause and consequences of a major Holocene abrupt climate change.” Quaternary Science Reviews 24.10-11 (2005): 1123-1149.  A prominent, abrupt climate event about 8200 years ago brought generally cold and dry conditions to broad northern-hemisphere regions especially in wintertime, in response to a very large outburst flood that freshened the North Atlantic. Changes were much larger than typical climate variability before and after the event, with anomalies up to many degrees contributing to major displacement of vegetative patterns. This “8k” event provides a clear case of cause and effect in the paleoclimatic realm, and so offers an excellent opportunity for model testing. The response to North Atlantic freshening has the same general anomaly pattern as observed for older events associated with abrupt climate changes following North Atlantic freshening, and so greatly strengthens the case that those older events also reflect North Atlantic changes. The North Atlantic involvement in the 8k event helps in estimating limits on climate anomalies that might result in the future if warming-caused ice-melt and hydrologic-cycle intensification at high latitudes lead to major changes in North Atlantic circulation. Few model experiments have directly addressed the 8k event, and most studies of proxy records across this event lack the time resolution to fully characterize the anomalies, so much work remains to be done.
  13. Chew, Sing C. “From Harappa to Mesopotamia and Egypt to Mycenae: Dark Ages, Political-Economic Declines, and Environmental/Climatic Changes 2200 BC–700 BC.” The Historical Evolution of World-Systems. Palgrave Macmillan, New York, 2005. 52-74.  Considerations of hegemonic decline as a world historical process most often attempt to account for decline and collapse of complex institutions in terms of social, political, and economic processes (Gills and Frank 1992). As we increasingly question whether there are physical–environmental limits that would affect the reproduction of world-systems, political, economic, and social dimensions might not be sufficient to account for hegemonic declines. Consideration of environmental and climatological factors needs to be combined with socioeconomic relations in our understanding of hegemonic declines and shifts. This approach assumes that the humans seek to transform nature in an expansive manner, and ceaselessly amass surpluses. There are certain long periods in world history that exhibit large economic and social crises and hegemonic decline. Such long periods of economic and social distress are here termed dark ages.
  14. Gorokhovich, Yuri. “Abandonment of Minoan palaces on Crete in relation to the earthquake induced changes in groundwater supply.” Journal of Archaeological Science 32.2 (2005): 217-222. Mysterious abandonment of palaces on Crete during the Late Minoan period was always a challenging problem for archeologists and geologists. Various hypotheses explained this event by effects of tsunamis, earthquakes or climatic changes that were caused by the volcanic eruption of the Santorini volcano. While each of them or their possible combination contributed to the abandonment of palaces and following Late Minoan crisis, there is another possible cause that appeared as a result of studies within the last 20–30 years. This cause is depletion of groundwater supply caused by persistent earthquake activity that took place during the Bronze Age. This explanation is supported by field observations and numerous studies of similar phenomena in other locations.
  15. Wanner, Heinz, et al. heinzWanner“Mid-to Late Holocene climate change: an overview.” Quaternary Science Reviews 27.19-20 (2008): 1791-1828.  The last 6000 years are of particular interest to the understanding of the Earth System because the boundary conditions of the climate system did not change dramatically (in comparison to larger glacial–interglacial changes), and because abundant, detailed regional palaeoclimatic proxy records cover this period. We use selected proxy-based reconstructions of different climate variables, together with state-of-the-art time series of natural forcings (orbital variations, solar activity variations, large tropical volcanic eruptions, land cover and greenhouse gases), underpinned by results from General Circulation Models (GCMs) and Earth System Models of Intermediate Complexity (EMICs), to establish a comprehensive explanatory framework for climate changes from the Mid-Holocene (MH) to pre-industrial time. The redistribution of solar energy, due to orbital forcing on a millennial timescale, was the cause of a progressive southward shift of the Northern Hemisphere (NH) summer position of the Intertropical Convergence Zone (ITCZ). This was accompanied by a pronounced weakening of the monsoon systems in Africa and Asia and increasing dryness and desertification on both continents. The associated summertime cooling of the NH, combined with changing temperature gradients in the world oceans, likely led to an increasing amplitude of the El Niño Southern Oscillation (ENSO) and, possibly, increasingly negative North Atlantic Oscillation (NAO) indices up to the beginning of the last millennium. On decadal to multi-century timescales, a worldwide coincidence between solar irradiance minima, tropical volcanic eruptions and decadal to multi-century scale cooling events was not found. However, reconstructions show that widespread decadal to multi-century scale cooling events, accompanied by advances of mountain glaciers, occurred in the NH (e.g., in Scandinavia and the European Alps). This occurred namely during the Little Ice Age (LIA) between AD ∼1350 and 1850, when the lower summer insolation in the NH, due to orbital forcing, coincided with solar activity minima and several strong tropical volcanic eruptions. The role of orbital forcing in the NH cooling, the southward ITCZ shift and the desertification of the Sahara are supported by numerous model simulations. Other simulations have suggested that the fingerprint of solar activity variations should be strongest in the tropics, but there is also evidence that changes in the ocean heat transport took place during the LIA at high northern latitudes, with possible additional implications for climates of the Southern Hemisphere (SH).
  16. ? Scafetta, Nicola. “Empirical evidence for a celestial origin of the climate oscillations and its implications.” Journal of Atmospheric and Solar-Terrestrial Physics 72.13 (2010): 951-970.  We investigate whether or not the decadal and multi-decadal climate oscillations have an astronomical origin. Several global surface temperature records since 1850 and records deduced from the orbits of the planets present very similar power spectra. Eleven frequencies with period between 5 and 100 years closely correspond in the two records. Among them, large climate oscillations with peak-to-trough amplitude of about 0.1 and 0.25°C, and periods of about 20 and 60 years, respectively, are synchronized to the orbital periods of Jupiter and Saturn. Schwabe and Hale solar cycles are also visible in the temperature records. A 9.1-year cycle is synchronized to the Moon’s orbital cycles. A phenomenological model based on these astronomical cycles can be used to well reconstruct the temperature oscillations since 1850 and to make partial forecasts for the 21st century. It is found that at least 60% of the global warming observed since 1970 has been induced by the combined effect of the above natural climate oscillations. The partial forecast indicates that climate may stabilize or cool until 2030–2040. Possible physical mechanisms are qualitatively discussed with an emphasis on the phenomenon of collective synchronization of coupled oscillators.
  17. Tsonis, A. A., et al. “Climate change and the demise of Minoan civilization.” Climate of the Past 6.4 (2010): 525-530.  Climate change has been implicated in the success and downfall of several ancient civilizations. Here we present a synthesis of historical, climatic, and geological evidence that supports the hypothesis that climate change may have been responsible for the slow demise of Minoan civilization. Using proxy ENSO and precipitation reconstruction data in the period 1650–1980 we present empirical and quantitative evidence that El Nino causes drier conditions in the area of Crete. This result is supported by modern data analysis as well as by model simulations. Though not very strong, the ENSO-Mediterranean drying signal appears to be robust, and its overall effect was accentuated by a series of unusually strong and long-lasting El Nino events during the time of the Minoan decline. Indeed, a change in the dynamics of the El Nino/Southern Oscillation (ENSO) system occurred around 3000 BC, which culminated in a series of strong and frequent El Nino events starting at about 1450 BC and lasting for several centuries. This stressful climatic trend, associated with the gradual demise of the Minoans, is argued to be an important force acting in the downfall of this classic and long-lived civilization.  FULL TEXT DOWNLOAD
  18. Wanner, Heinz, et al. “Structure and origin of Holocene cold events.” Quaternary Science Reviews 30.21-22 (2011): 3109-3123. The present interglacial, the Holocene, spans the period of the last 11,700 years. It has sustained the growth and development of modern society. The millennial-scale decreasing solar insolation in the Northern Hemisphere summer lead to Northern Hemisphere cooling, a southern shift of the Intertropical Convergence Zone (ITCZ) and a weakening of the Northern Hemisphere summer monsoon systems. On the multidecadal to multicentury-scale, periods of more stable and warmer climate were interrupted by several cold relapses, at least in the Northern Hemisphere extra-tropical area. Based on carefully selected 10,000-year-long time series of temperature and humidity/precipitation, as well as reconstructions of glacier advances, the spatiotemporal pattern of six cold relapses during the last 10,000 years was analysed and presented in form of a Holocene Climate Atlas (HOCLAT; see http://www.oeschger.unibe.ch/research/projects/holocene_atlas/). A clear cyclicity was not found, and the spatiotemporal variability of temperature and humidity/precipitation during the six specific cold events (8200, 6300, 4700, 2700, 1550 and 550 years BP) was very high. Different dynamical processes such as meltwater flux into the North Atlantic, low solar activity, explosive volcanic eruptions, and fluctuations of the thermohaline circulation likely played a major role. In addition, internal dynamics in the North Atlantic and Pacific area (including their complex interaction) were likely involved. AUTHOR’S NOTES: {Based on temperature, humidity and glacier data, we analyze Holocene cold events. During the Holocene a clear cyclicity between warm and cold periods was not found.  Single cold relapses are subject to different dynamical processes. The six analyzed cold events show different spatial structures.}
  19. Humlum, Ole, Jan-Erik Solheim, and Kjell Stordahl. “Identifying natural contributions to late Holocene climate change.” Global and Planetary Change 79.1-2 (2011): 145-156.  Analytic climate models have provided the means to predict potential impacts on future climate by anthropogenic changes in atmospheric composition. However, future climate development will not only be influenced by anthropogenic changes, but also by natural variations. The knowledge on such natural variations and their detailed character, however, still remains incomplete. Here we present a new technique to identify the character of natural climate variations, and from this, to produce testable forecast of future climate. By means of Fourier and wavelet analyses climate series are decomposed into time–frequency space, to extract information on periodic signals embedded in the data series and their amplitude and variation over time. We chose to exemplify the potential of this technique by analysing two climate series, the Svalbard (78°N) surface air temperature series 1912–2010, and the last 4000 years of the reconstructed GISP2 surface temperature series from central Greenland. By this we are able to identify several cyclic climate variations which appear persistent on the time scales investigated. Finally, we demonstrate how such persistent natural variations can be used for hindcasting and forecasting climate. Our main focus is on identifying the character (timing, period, amplitude) of such recurrent natural climate variations, but we also comment on the likely physical explanations for some of the identified cyclic climate variations. The causes of millennial climate changes remain poorly understood, and this issue remains important for understanding causes for natural climate variability over decadal- and decennial time scales. We argue that Fourier and wavelet approaches like ours may contribute towards improved understanding of the role of such recurrent natural climate variations in the future climate development.
  20. Drake, Brandon L. “The influence of climatic change on the Late Bronze Age Collapse and the Greek Dark Ages.” Journal of Archaeological Science 39.6 (2012): 1862-1870.  Between the 13th and 11th centuries BCE, most Greek Bronze Age Palatial centers were destroyed and/or abandoned. The following centuries were typified by low population levels. Data from oxygen-isotope speleothems, stable carbon isotopes, alkenone-derived seasurface temperatures, and changes in warm-species dinocysts and formanifera in the Mediterranean indicate that the Early Iron Age was more arid than the preceding Bronze Age. A sharp increase in Northern Hemisphere temperatures preceded the collapse of Palatial centers, a sharp decrease occurred during their abandonment. Mediterranean Seasurface temperatures cooled rapidly during the Late Bronze Age, limiting freshwater flux into the atmosphere and thus reducing precipitation over land. These climatic changes could have affected Palatial centers that were dependent upon high levels of agricultural productivity. Declines in agricultural production would have made higher-density populations in Palatial centers unsustainable. The ‘Greek Dark Ages’ that followed occurred during prolonged arid conditions that lasted until the Roman Warm Period.

 

 

EARLY HOLOCENE SEA LEVEL RISE & 8.2K EVENT

 

  1. Hori, KazuakiHori, Kazuaki, and Yoshiki Saito. “An early Holocene sea‐level jump and delta initiation.” Geophysical Research Letters 34.18 (2007).  Early Holocene sea‐level change controlled the evolution of classic coastal depositional systems. Radiocarbon‐dated borehole cores obtained from three incised‐valley‐fill systems in Asia (Changjiang, Song Hong, and Kiso River) record very similar depositional histories, especially between about 9000 and 8500 cal BP. Sedimentary facies changes from estuarine sand and mud to shelf or prodelta mud suggest that the marine influence in the incised valleys increased during this period. In addition, large decreases in sediment accumulation rates occurred. A sea‐level jump causes an estuarine system and its depocenter to move rapidly landward. It is possible that the final collapse of the Laurentide Ice Sheet, accompanied by catastrophic drainage of glacial lakes, at approximately 8500 cal BP caused such a jump. The jump was followed immediately by a period of decelerated sea‐level rise that promoted delta initiation.
  2. Vink, AnnemiekVink, Annemiek, et al. “Holocene relative sea-level change, isostatic subsidence and the radial viscosity structure of the mantle of northwest Europe (Belgium, the Netherlands, Germany, southern North Sea).” Quaternary Science Reviews26.25-28 (2007): 3249-3275.  A comprehensive observational database of Holocene relative sea-level (RSL) index points from northwest Europe (Belgium, the Netherlands, northwest Germany, southern North Sea) has been compiled in order to compare and reassess the data collected from the different countries/regions and by different workers on a common time–depth scale. RSL rise varies in magnitude and form between these regions, revealing a complex pattern of differential crustal movement which cannot be solely attributed to tectonic activity. It clearly contains a non-linear, glacio- and/or hydro-isostatic subsidence component, which is only small on the Belgian coastal plain but increases significantly to a value of ca 7.5 m relative to Belgium since 8 cal. ka BP along the northwest German coast. The subsidence is at least in part related to the Post-Glacial collapse of the so-called peripheral forebulge which developed around the Fennoscandian centre of ice loading during the Last Glacial Maximum. The RSL data have been compared to geodynamic Earth models in order to infer the radial viscosity structure of the Earth’s mantle underneath NW Europe (lithosphere thickness, upper- and lower-mantle viscosity), and conversely to predict RSL in regions where we have only few observational data (e.g. in the southern North Sea). A very broad range of Earth parameters fit the Belgian RSL data, suggesting that glacial isostatic adjustment (GIA) only had a minor effect on Belgian crustal dynamics during and after the Last Ice Age. In contrast, a narrow range of Earth parameters define the southern North Sea region, reflecting the greater influence of GIA on these deeper/older samples. Modelled RSL data suggest that the zone of maximum forebulge subsidence runs in a relatively narrow, WNW–ESE trending band connecting the German federal state of Lower Saxony with the Dogger Bank area in the southern North Sea. Identification of the effects of local-scale factors such as past changes in tidal range or tectonic activity on the spatial and temporal variations of sea-level index points based on model-data comparisons is possible but is still complicated by the relatively large range of Earth model parameters fitting each RSL curve, emphasizing the need for more high-quality observational data.
  3. Kendall, Roblyn A., et al. “The sea-level fingerprint of the 8.2 ka climate event.” Geology 36.5 (2008): 423-426.  The 8.2 ka cooling event was an abrupt, widespread climate instability. There is general consensus that the episode was likely initiated by a catastrophic outflow of proglacial Lakes Agassiz and Ojibway through the Hudson Strait, with subsequent disruption of the Atlantic meridional overturning circulation. However, the total discharge and flux during the 8.2 ka event remain uncertain. We compute the sea-level signature, or “fingerprint,” associated with the drainage of Lakes Agassiz and Ojibway, as well as the expected sea-level signal over the same time period due to glacial isostatic adjustment (GIA) in response to the Late Pleistocene deglaciation. Our analysis demonstrates that sites relatively close to the lakes, including the West and Gulf Coasts of the United States, have small signals due to the lake release and potentially large GIA signals, and thus they may not be optimal field sites for constraining the outflow volume. Other sites, such as the east coast of South America and western Africa, have significantly larger signals associated with the lake release and are thus better choices in this regard.
  4. Hijma, Marc Phijma-mark., and Kim M. Cohen. “Timing and magnitude of the sea-level jump preluding the 8200 yr event.” Geology 38.3 (2010): 275-278.  Evidence from terrestrial, glacial, and global climate model reconstructions suggests that a sea-level jump caused by meltwater release was associated with the triggering of the 8.2 ka cooling event. However, there has been no direct measurement of this jump using precise sea-level data. In addition, the chronology of the meltwater pulse is based on marine data with limited dating accuracy. The most plausible mechanism for triggering the cooling event is the sudden, possibly multistaged drainage of the Laurentide proglacial Lakes Agassiz and Ojibway through the Hudson Strait into the North Atlantic ca. 8470 ± 300 yr ago. Here we show with detailed sea-level data from Rotterdam, Netherlands, that the sea-level rise commenced 8450 ± 44 yr ago. Our timing considerably narrows the existing age of this drainage event and provides support for the hypothesis of a double-staged lake drainage. The jump in sea level reached a local magnitude of 2.11 ± 0.89 m within 200 yr, in addition to the ongoing background relative sea-level rise (1.95 ± 0.74 m). This magnitude, observed at considerable distance from the release site, points to a global-averaged eustatic sea-level jump that is double the size of previous estimates (3.0 ± 1.2 m versus 0.4–1.4 m). The discrepancy suggests either a coeval Antarctic contribution or, more likely, a previous underestimate of the total American lake drainage.
  5. Bard, Edouardeduard, Bruno Hamelin, and Doriane Delanghe-Sabatier. “Deglacial meltwater pulse 1B and Younger Dryas sea levels revisited with boreholes at Tahiti.” Science327.5970 (2010): 1235-1237.  Reconstructing sea-level changes during the last deglaciation provides a way of understanding the ice dynamics that can perturb large continental ice sheets. The resolution of the few sea-level records covering the critical time interval between 14,000 and 9,000 YBP calendar years before the present is still insufficient to draw conclusions about sea-level changes associated with the Younger Dryas cold event and the meltwater pulse 1B (MWP-1B). We used the uranium-thorium method to date shallow-living corals from three new cores drilled onshore in the Tahiti barrier reef. No significant discontinuity can be detected in the sea-level rise during the MWP-1B period. The new Tahiti sea-level record shows that the sea-level rise slowed down during the Younger Dryas before accelerating again during the Holocene.
  6. Smith, D. E., et al. “The early Holocene sea level rise.” Quaternary Science Reviews 30.15-16 (2011): 1846-1860.  The causes, anatomy and consequences of the early Holocene sea level rise (EHSLR) are reviewed. The rise, of ca 60m, took place over most of the Earth as the volume of the oceans increased during deglaciation and is dated at 11,650–7000 cal. BP. The EHSLR was largely driven by meltwater release from decaying ice masses and the break up of coastal ice streams. The patterns of ice sheet decay and the evidence for meltwater pulses are reviewed, and it is argued that the EHSLR was a factor in the ca 8470 BP flood from Lake Agassiz-Ojibway. Patterns of relative sea level changes are examined and it is argued that in addition to regional variations, temporal changes are indicated. The impact of the EHSLR on climate is reviewed and it is maintained that the event was a factor in the 8200 BP cooling event, as well as in changes in ocean current patterns and their resultant effects. The EHSLR may also have enhanced volcanic activity, but no clear evidence of a causal link with submarine sliding on continental slopes and shelves can yet be demonstrated. The rise probably influenced rates and patterns of human migrations and cultural changes. It is concluded that the EHSLR was a major event of global significance, knowledge of which is relevant to an understanding of the impacts of global climate change in the future. Highlights:  1. Reviews the early Holocene sea level rise of 11650–7000 cal. BP. 2. Argues that the rise was involved in the discharge of Lake Agassiz-Ojibway and the 8200-year cooling event. 3. Shows that he rise influenced climate by increasing sea areas, in turn affecting human migration. 4. Suggests that the rise increased volcanic activity, but that its effects on submarine sliding are uncertain. 5. Argues that study of the rise helps throw light on the effects of future sea level changes in a global warming world.
  7. Hijma, Marchijma-mark P., and Kim M. Cohen. “Holocene transgression of the Rhine river mouth area, The Netherlands/Southern North Sea: palaeogeography and sequence stratigraphy.” Sedimentology 58.6 (2011): 1453-1485.  This study presents a detailed reconstruction of the palaeogeography of the Rhine valley (western Netherlands) during the Holocene transgression with systems tracts placed in a precise sea‐level context. This approach permits comparison of actual versus conceptual boundaries of the lowstand, transgressive and highstand systems tracts. The inland position of the highstand Rhine river mouth on a wide, low‐gradient continental shelf meant that base‐level changes were the dominant control on sedimentation for a relatively short period of the last glacial cycle. Systems in such inland positions predominantly record changes in the balance between river discharge and sediment load, and preserve excellent records of climatic changes or other catchment‐induced forcing. It is shown here that the transgressive systems tract‐part of the coastal prism formed in three stages: (i) the millennium before 8·45 ka bp, when the area was dominated by fluvial environments with extensive wetlands; (ii) the millennium after 8·45 ka, characterized by strong erosion, increasing tidal amplitudes and bay‐head delta development; and (iii) the period between 7·5 and 6·3 ka bp when the Rhine avulsed multiple times and the maximum flooding surface formed. The diachroneity of the transgressive surface is strongly suppressed because of a pulse of accelerated sea‐level rise at 8·45 ka bp. That event not only had a strong effect on preservation, but has circum‐oceanic stratigraphical relevance as it divides the early and middle Holocene parts of coastal successions worldwide. The palaeogeographical reconstruction offers a unique full spatial–temporal view on the coastal and fluvial dynamics of a major river mouth under brief rapid forced transgression. This reconstruction is of relevance for Holocene and ancient transgressive systems worldwide, and for next‐century natural coasts that are predicted to experience a 1 m sea‐level rise.
  8. Hijma, Marchijma-mark P., et al. “Pleistocene Rhine–Thames landscapes: geological background for hominin occupation of the southern North Sea region.” Journal of Quaternary Science 27.1 (2012): 17-39.  This paper links research questions in Quaternary geology with those in Palaeolithic archaeology. A detailed geological reconstruction of The Netherlands’ south‐west offshore area provides a stratigraphical context for archaeological and palaeontological finds. Progressive environmental developments have left a strong imprint on the area’s Palaeolithic record. We highlight aspects of landscape evolution and related taphonomical changes, visualized in maps for critical periods of the Pleistocene in the wider southern North Sea region. The Middle Pleistocene record is divided into two palaeogeographical stages: the pre‐Anglian/Elsterian stage, during which a wide land bridge existed between England and Belgium even during marine highstands; and the Anglian/Elsterian to Saalian interglacial, with a narrower land bridge, lowered by proglacial erosion but not yet fully eroded. The Late Pleistocene landscape was very different, with the land bridge fully dissected by an axial Rhine–Thames valley, eroded deep enough to fully connect the English Channel and the North Sea during periods of highstand. This tripartite staging implies great differences in (i) possible migration routes of herds of herbivores as well as hominins preying upon them, (ii) the erosion base of axial and tributary rivers causing an increase in the availability of flint raw materials and (iii) conditions for loess accumulation in northern France and Belgium and the resulting preservation of Middle Palaeolithic sites.
  9. Törnqvist, TorbjörnTörnqvist, Torbjörn E., and Marc P. Hijma. “Links between early Holocene ice-sheet decay, sea-level rise and abrupt climate change.” Nature Geoscience 5.9 (2012): 601.  The beginning of the current interglacial period, the Holocene epoch, was a critical part of the transition from glacial to interglacial climate conditions. This period, between about 12,000 and 7,000 years ago, was marked by the continued retreat of the ice sheets that had expanded through polar and temperate regions during the preceding glacial. This meltdown led to a dramatic rise in sea level, punctuated by short-lived jumps associated with catastrophic ice-sheet collapses. Tracking down which ice sheet produced specific sea-level jumps has been challenging, but two events between 8,500 and 8,200 years ago have been linked to the final drainage of glacial Lake Agassiz in north-central North America. The release of the water from this ice-dammed lake into the ocean is recorded by sea-level jumps in the Mississippi and Rhine-Meuse deltas of approximately 0.4 and 2.1 metres, respectively. These sea-level jumps can be related to an abrupt cooling in the Northern Hemisphere known as the 8.2 kyr event, and it has been suggested that the freshwater release from Lake Agassiz into the North Atlantic was sufficient to perturb the North Atlantic meridional overturning circulation. As sea-level rise on the order of decimetres to metres can now be detected with confidence and linked to climate records, it is becoming apparent that abrupt climate change during the early Holocene associated with perturbations in North Atlantic circulation required sustained freshwater release into the ocean.
  10. Sturt, FraserSturt, Fraser, Duncan Garrow, and Sarah Bradley. “New models of North West European Holocene palaeogeography and inundation.” Journal of Archaeological Science 40.11 (2013): 3963-3976. Highlights: New Palaeogeographic models of North West Europe from 11,000 BP to present day at 500 year intervals. Calculated rates for Holocene inundation across North West Europe. High rates of change do not necessarily mean catastrophic impacts. Understanding rates of change and their social implications requires a multi-scalar, multidisciplinary approach to the past.Abstract: This paper presents new 500 year interval palaeogeographic models for Britain, Ireland and the North West French coast from 11000 cal. BP to present. These models are used to calculate the varying rates of inundation for different geographical zones over the study period. This allows for consideration of the differential impact that Holocene sea-level rise had across space and time, and on past societies. In turn, consideration of the limitations of the models helps to foreground profitable areas for future research.

 

 

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3 Responses to "A Chaotic Holocene Climate?"

[…] the last glaciation. A graphical representation of the last glaciation appears in a related post [LINK] . According to research by the DRI, these eruptions altered the ocean currents and the climate of […]

[…] chaotic cycles of ice accumulation and ice dissipation discussed in a related post on this site [LINK] . The information presented below is taken from a lecture on a geological explanation of […]

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