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Hydrologic Variations of South America's Lake Titicaca
Reference
Baker, P.A., Fritz, S.C., Garland, J. and Ekdahl, E. 2005. Holocene hydrologic variation at Lake Titicaca, Bolivia/Peru, and its relationship to North Atlantic climate variation. Journal of Quaternary Science 207: 655-662.

What was done
Working with a sediment core retrieved from the main basin of Lake Titicaca (16°S, 69°W) on the Altiplano of Bolivia and Peru, the authors reconstructed the lake-level history of the famous South American water body over the last 13,000 years at decadal to multi-decadal resolution based on δ13C measurements of sediment bulk organic matter.

What was learned
Baker et al. report that "the pattern and timing of lake-level change in Lake Titicaca is similar to the ice-rafted debris record of Holocene Bond events, demonstrating a possible coupling between precipitation variation on the Altiplano and North Atlantic sea-surface temperatures." Noting that "cold periods of the Holocene Bond events correspond with periods of increased precipitation on the Altiplano," they further conclude that "Holocene precipitation variability on the Altiplano is anti-phased with respect to precipitation in the Northern Hemisphere monsoon region." In further support of these findings, they add that "the relationship between lake-level variation at Lake Titicaca and Holocene Bond events also is supported by the more coarsely resolved (but very well documented) record of water-level fluctuations over the past 4000 years based on the sedimentology of cores from the shallow basin of the lake (Abbott et al., 1997)."

What it means
In a recent review of possible solar effects on earth's climate, Foukal et al. (2006) note that "evidence for the influence of the sun on climate has recently been extended by a millennial-scale correlation found between North Atlantic climate (inferred from the properties of deep sea sediments) and solar activity (inferred from 10Be and 14C), extending back about 10,000 years (Bond et al., 2001)," but they say "it remains to be seen whether the correlation is confined to the North Atlantic, or is global." The findings of Baker et al. (published a year before the Foukal et al. paper, but not cited by them) go a long way toward demonstrating that the appropriate spatial scale is indeed global. In fact, Bond et al. themselves pointed out that prior studies conducted in Oman, coastal West Africa, the Cariaco Basin, equatorial East Africa, and the Yucatan Peninsula had already demonstrated that "the footprint of the solar impact on climate," which was documented by them to exist throughout the North Atlantic, extends all the way "to tropical latitudes." In addition, they clearly stated that "over the last 12,000 years virtually every [our italics] centennial time-scale increase in drift ice documented in our North Atlantic records was tied to a solar minimum." In light of these observations, Bond et al. concluded, and rightly so, that "a solar influence on climate of the magnitude and consistency implied by our evidence could not have been confined to the North Atlantic," which conclusion now appears to be well supported by numerous confirmatory studies from all around the world.

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

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.

Foukal, P., Frohlich, C., Spruit, H. and Wigley, T.M.L. 2006. Variations in solar luminosity and their effect on the earth's climate. Nature 443: 161-166.

Reviewed 3 January 2007