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Climate Oscillations (Millennial Variability - South America) -- Summary
That the North Atlantic Ocean and surrounding lands have experienced a millennial-scale oscillation of climate from time immemorial, extending through glacial and interglacial periods alike, is a well-established fact (Bond et al., 1997; Oppo et al., 1998; Raymo et al., 1998; Bianchi and McCave, 1999; McManus et al., 1999; Keigwin and Boyle, 2000; Bond et al., 2001; McDermott et al., 2001; Andersson et al., 2003; Dokken et al., 2003). Moreover, the incredible regularity of this oscillation between relatively warmer and cooler states literally cries out for an extraterrestrial explanation, which further suggests that the cyclic phenomenon should be evident most everywhere on the planet; for an other-worldly forcing factor, such as cyclical variations in solar activity, would have to be manifest on a much broader geographic scale than merely the North Atlantic Ocean and its immediate environs. And so it is, with one of the more engaging examples of the forever-recurring climatic oscillation coming from a study of the in-filled basin of the ancient Inca's sacred lake of Marcacocha, which is located high in the Central Andean region of Peru some 45 km northwest of the legendary city of Cuzco.

Different aspects of this intriguing study are described by Chepstow-Lusty et al. (1998, 2003) and Chepstow-Lusty and Winfield (2000), who measured and analyzed various indicators of past climatic conditions in a highly-organic sediment core extracted from the center of the in-filled Marcacocha basin in 1993. Centered on approximately 1000 years ago, they identified what Chepstow-Lusty and Winfield describe as "the warm global climatic interval frequently referred to as the Medieval Warm Epoch," which arid interval in this part of South America may have played a significant role in the collapse of the Tiwanaku civilization further south, where a contemporaneous prolonged drought occurred in and around the area of Lake Titicaca (Binford et al., 1997; Abbott et al., 1997).

Near the start of this extended dry period, which had gradually established itself between about AD 700 and 1000, Chepstow-Lusty and Winfield report that "temperatures were beginning to increase after a sustained cold period that had precluded agricultural activity at these altitudes." This earlier colder and wetter interval was coeval with the Dark Ages Cold Period of the North Atlantic region, which in the Peruvian Andes had held sway for a good portion of the millennium preceding AD 1000, as revealed by a series of climatic records developed from sediment cores extracted from other lakes in the Central Peruvian Andes (Hansen et al., 1994) and by proxy evidence of concomitant Peruvian glacial expansion (Wright, 1984; Seltzer and Hastorf, 1990).

Preceding the Dark Ages Cold Period in both parts of the world was what in the North Atlantic region is called the Roman Warm Period. This well-defined climatic epoch is strikingly evident in the pollen records of Chepstow-Lusty et al. (2003), straddling the BC/AD calendar break with one to two hundred years of relative warmth and significant aridity located on either side of it.

Returning to the Medieval Warm Period and preceding towards the present, the data of Chepstow-Lusty et al. (2003) reveal the occurrence of the Little Ice Age, which in the Central Peruvian Andes was characterized by relative coolness and wetness. These characteristics of that climatic interval are also evident in ice cores retrieved from the Quelccaya ice cap in southern Peru, the summit of which extends 5670 meters above mean sea level (Thompson et al., 1986, 1988). In addition, both the Quelccaya ice core data and the Marcacocha pollen data reveal the transition to the drier Current Warm Period that occurred over the past 100-plus years.

Over in Chile, Jenny et al. (2002) studied geochemical, sedimentological and diatom-assemblage data derived from sediment cores extracted from one of the largest natural lakes in the central part of that country (Laguna Aculeo), in order to obtain information about the hydrologic climate of the region over the past two millennia. Their work revealed that from 200 BC, when the record began, until AD 200, conditions were primarily dry during what we know to be the latter part of the Roman Warm Period. Subsequently, from AD 200-700, with a slight respite in the central hundred years of that period, there was a high frequency of flood events that coincided with the Dark Ages Cold Period. Then came a several-hundred-year period of less flooding that was coeval with the Medieval Warm Period. This more benign period was then followed by another period of frequent flooding from 1300-1700, which picked up again about 1850 and which was of the same timeframe as the Little Ice Age.

Glasser et al. (2004) described a large body of evidence related to glacier fluctuations in the two major ice fields of Patagonia: the Hielo Patagonico Norte (4700'S, 7339'W) and the Hielo Patagonico Sur (between 4850'S and 5130'S). This evidence indicates that the most recent glacial advances in Patagonia occurred during the Little Ice Age, out of which serious cold spell the earth has been gradually emerging for the past two centuries, causing many glaciers to retreat. Prior to the Little Ice Age, however, there was an interval of higher temperatures during the Medieval Warm Period, when glaciers also decreased in size and extent; and this warm interlude was in turn preceded by a still earlier era of pronounced glacial activity during the Dark Ages Cold Period, which was preceded by an era of higher temperatures and retreating glaciers during the Roman Warm Period.

Prior to the Roman Warm Period, Glasser et al.'s presentation of the pertinent evidence suggests there was another period of significant glacial advance that also lasted several hundred years, which was preceded by a several-century interval when glaciers once again lost ground, which was preceded by yet another multi-century period of glacial advance, which was preceded by yet another long interval of glacier retrenchment, which was preceded by still another full cycle of such temperature-related glacial activity, which at this point brings us all the way back to sometime between 6000 and 5000 14C years before the present (BP).

Glasser et al. additionally cite the works of a number of other scientists that reveal a similar pattern of cyclical glacial activity over the preceding millennia in several other locations. Immediately to the east of the Hielo Patagonico Sur in the Rio Guanaco region of the Precordillera, for example, they report that Wenzens (1999) detected five distinct periods of glacial advancement: "4500-4200, 3600-3300, 2300-2000, 1300-1000 14C years BP and AD 1600-1850." With respect to the glacial advancements that occurred during the cold interval that preceded the Roman Warm Period, they say they are "part of a body of evidence for global climatic change around this time (e.g., Grosjean et al., 1998; Wasson and Claussen, 2002), which coincides with an abrupt decrease in solar activity," adding that this observation "led van Geel et al. (2000) to suggest that variations in solar irradiance are more important as a driving force in variations in climate than previously believed."

Last of all, with respect to the most recent recession of Hielo Patogonico Norte outlet glaciers from their late historic moraine limits at the end of the 19th century, Glasser et al. say that "a similar pattern can be observed in other parts of southern Chile (e.g., Kuylenstierna et al., 1996; Koch and Kilian, 2001)." Likewise, they note that "in areas peripheral to the North Atlantic and in central Asia the available evidence shows that glaciers underwent significant recession at this time (cf. Grove, 1988; Savoskul, 1997)," which again suggests the operation of a globally-distributed forcing factor such as cyclically-variable solar activity.

In concluding their study, Glasser et al. consider a number of "possible explanations for the patterns of observed glacier fluctuations." Since so many factors come into play in this regard, however, and since a good percentage of glaciers refuse to respond as their neighbors do, it is difficult to provide a "one size fits all" explanation for their behavior. Nevertheless, in as close as one can come to framing a general conclusion on this point, Glasser et al. state that "proxy climate data indicate that many of these broad regional trends can be explained by changes in precipitation and atmospheric temperature rather than systematic changes related to the internal characteristics of the ice fields."

In conclusion, extensive climatic correspondences such as those described in the paragraphs above, occurring between widely separated Northern and Southern Hemispheric regions, are not coincidental; they reveal the existence of a significant millennial-scale oscillation of climate that is global in scope and, hence, likely the result of a regularly-varying extraterrestrial forcing factor. Although one can argue about the identity of that factor and the means by which it exerts its influence, one thing is clear: the causative factor is not the atmosphere's CO2 concentration, which has only varied in phase with the climatic oscillation over the Little Ice Age-to-Current Warm Period transition, and which has exhibited no cyclicity at all over the entire rest of the record. This being the case, it should be clear to everyone that the climatic amelioration of the past century or more has likely had nothing to do with the concomitant rise in the air's CO2 content but probably everything to do with the influential extraterrestrial forcing factor that has governed the millennial-scale oscillation of earth's climate as far back in time as researchers have been able to detect it.

References
Abbott, M.B., Binford, M.W., Brenner, M. and Kelts, K.R. 1997. A 3500 14C yr high resolution record of water-level changes in Lake Titicaca. Quaternary Research 47: 169-180.

Andersson, C., Risebrobakken, B., Jansen, E. and Dahl, S.O. 2003. Late Holocene surface ocean conditions of the Norwegian Sea (Voring Plateau). Paleoceanography 18: 10.1029/2001PA000654.

Bianchi, G.G. and McCave, I.N. 1999. Holocene periodicity in North Atlantic climate and deep-ocean flow south of Iceland. Nature 397: 515-517.

Binford, M.W., Kolata, A.L, Brenner, M., Janusek, J.W., Seddon, M.T., Abbott, M. and Curtis. J.H. 1997. Climate variation and the rise and fall of an Andean civilization. Quaternary Research 47: 235-248.

Bond, G., Kromer, B., Beer, J., Muscheler, R., Evans, M.N., Showers, W., Hoffmann, S., Lotti-Bond, R., Hajdas, I. and Bonani, G. 2001. Persistent solar influence on North Atlantic climate during the Holocene. Science 294: 2130-2136.

Bond, G., Showers, W., Chezebiet, M., Lotti, R., Almasi, P., deMenocal, P., Priore, P., Cullen, H., Hajdas, I. and Bonani, G. 1997. A pervasive millennial scale cycle in North-Atlantic Holocene and glacial climates. Science 278: 1257-1266.

Chepstow-Lusty, A.J., Bennett, K.D., Fjeldsa, J., Kendall, A., Galiano, W. and Herrera, A.T. 1998. Tracing 4,000 years of environmental history in the Cuzco Area, Peru, from the pollen record. Mountain Research and Development 18: 159-172.

Chepstow-Lusty, A., Frogley, M.R., Bauer, B.S., Bush, M.B. and Herrera, A.T. 2003. A late Holocene record of arid events from the Cuzco region, Peru. Journal of Quaternary Science 18: 491-502.

Chepstow-Lusty, A. and Winfield, M. 2000. Inca agroforestry: Lessons from the past. Ambio 29: 322-328.

Dokken, T., Andrews, J., Hemming, S., Stokes, C. and Jansen, E. 2003. Researchers discuss abrupt climate change: Ice sheets and oceans in action. EOS, Transactions, American Geophysical Union 84: 189, 193.

Glasser, N.F., Harrison, S., Winchester, V. and Aniya, M. 2004. Late Pleistocene and Holocene palaeoclimate and glacier fluctuations in Patagonia. Global and Planetary Change 43: 79-101.

Grosjean, M., Geyh, M.A., Messerli, B., Schreier, H. and Veit, H. 1998. A late-Holocene (~2600 BP) glacial advance in the south-central Andes (29S), northern Chile. The Holocene 8: 473-479.

Grove, J.M. 1988. The Little Ice Age. Routledge, London, UK.

Hansen, B.C.S., Seltzer, G.O. and Wright Jr., H.E. 1994. Late Quaternary vegetational change in the central Peruvian Andes. Palaeogeography, Palaeoclimatology, Palaeoecology 109: 263-285.

Jenny, B., Valero-Garces, B.L., Urrutia, R., Kelts, K., Veit, H., Appleby, P.G. and Geyh M. 2002. Moisture changes and fluctuations of the Westerlies in Mediterranean Central Chile during the last 2000 years: The Laguna Aculeo record (3350'S). Quaternary International 87: 3-18.

Keigwin, L.D. and Boyle, E.A. 2000. Detecting Holocene changes in thermohaline circulation. Proceedings of the National Academy of Sciences USA 97: 1343-1346.

Koch, J. and Kilian, R. 2001. Dendroglaciological evidence of Little Ice Age glacier fluctuations at the Gran Campo Nevado, southernmost Chile. In: Kaennel Dobbertin, M. and Braker, O.U. (Eds.), International Conference on Tree Rings and People. Davos, Switzerland, p. 12.

Kuylenstierna, J.L., Rosqvist, G.C. and Holmlund, P. 1996. Late-Holocene glacier variations in the Cordillera Darwin, Tierra del Fuego, Chile. The Holocene 6: 353-358.

McDermott, F., Mattey, D.P. and Hawkesworth, C. 2001. Centennial-scale Holocene climate variability revealed by a high-resolution speleothem δ18O record from SW Ireland. Science 294: 1328-1331.

McManus, J.F., Oppo, D.W. and Cullen, J.L. 1999. A 0.5-million-year record of millennial-scale climate variability in the North Atlantic. Science 283: 971-974.

Oppo, D.W., McManus, J.F. and Cullen, J.L. 1998. Abrupt climate events 500,000 to 340,000 years ago: Evidence from subpolar North Atlantic sediments. Science 279: 1335-1338.

Raymo, M.E., Ganley, K., Carter, S., Oppo, D.W. and McManus, J. 1998. Millennial-scale climate instability during the early Pleistocene epoch. Nature 392: 699-702.

Seltzer, G. and Hastorf, C. 1990. Climatic change and its effect on Prehispanic agriculture in the central Peruvian Andes. Journal of Field Archaeology 17: 397-414.

Savoskul, O.S. 1997. Modern and Little Ice Age glaciers in "humid" and "arid" areas of the Tien Shan, Central Asia: two different patterns of fluctuation. Annals of Glaciology 24: 142-147.

Thompson, L.G., Mosley-Thompson, E., Dansgaard, W. and Grootes, P.M. 1986. The Little Ice Age as recorded in the stratigraphy of the tropical Quelccaya ice cap. Science 234: 361-364.

Thompson, L.G., Davis, M.E., Mosley-Thompson, E. and Liu, K.-B. 1988. Pre-Incan agricultural activity recorded in dust layers in two tropical ice cores. Nature 307: 763-765.

van Geel, B., Heusser, C.J., Renssen, H. and Schuurmans, C.J.E. 2000. Climatic change in Chile at around 2700 B.P. and global evidence for solar forcing: a hypothesis. The Holocene 10: 659-664.

Wasson, R.J. and Claussen, M. 2002. Earth systems models: a test using the mid-Holocene in the Southern Hemisphere. Quaternary Science Reviews 21: 819-824.

Wenzens, G. 1999. Fluctuations of outlet and valley glaciers in the southern Andes (Argentina) during the past 13,000 years. Quaternary Research 51: 238-247.

Wright Jr., H.E. 1984. Late glacial and Late Holocene moraines in the Cerros Cuchpanga, central Peru. Quaternary Research 21: 275-285.

Last updated 27 June 2007