Stable Isotope, Pollen and Charcoal Records of Middle-to-Late Holocene Hydroclimate Variability from Lake Kail in the Western Guatemala Highlands
Abstract
A long-term perspective of past hydroclimate variability in Central America provides context for evaluating the potential future impacts of changes in Northern Hemisphere temperatures and mean-state ocean-atmospheric conditions. Here we use the isotopic composition of fine-grained (< 63 μm) endogenic CaCO3 (δ18Ocalcite and δ13Ccalcite) from Lake Kail in the western highlands of Guatemala to infer multi-decadal to multi-centennial-scale changes in the balance of precipitation and evaporation (P/E) over the last ~6000 years. We also reconstructed past vegetation, anthropogenic use of fire, and faunal abundance using proxy analysis of fossil pollen, macroscopic charcoal, microscopic charcoal. The sediment age model is based on 210Pb and 41 14C ages, with chronological uncertainty estimated using Bayesian methods. The δ18Ocalcite variations demonstrate slightly drier conditions from ~6000 to 4600 cal yr BP, followed by a wetter climate until ~4200 cal yr BP. There was an abrupt shift to drier conditions at ~4200 cal yr BP, with a stepwise shift to higher P/E until ~3000 cal yr BP. Climate was less variable and wet overall from ~3000 to 2800 cal yr BP, after which there was more variable climate and a trend to drier conditions until ~2000 cal yr BP. There was a trend to wetter and less variable conditions from 2000 to 1400 cal yr BP, and the climate remained comparatively wet during the last ~1400 years, with the wettest conditions from ~400 to 250 cal yr BP. We also found that forests within the Southern Maya area were transformed by Pre-Columbian human populations through practices of agriculture and architectural developments over thousands of years. Moreover, results from this study indicate that fire, rather than hydroclimate, has been the most important driver of vegetative change in this ecosystem throughout the last ~6000 years. Comparisons of the Lake Kail δ18Ocalcite record with regional proxy datasets spanning the middle-late Holocene indicate there was a highly variable pattern of northern tropical hydroclimate changes during the middle-to-late Holocene that is inconsistent with direct insolation forcing. Higher frequency, multi-decadal and multi-centennial-scale variability in the Lake Kail δ18Ocalcite record was likely driven by non-linear responses to ocean-atmospheric processes.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMPP24B..03S
- Keywords:
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- 1616 Climate variability;
- GLOBAL CHANGE;
- 4943 Paleolimnology;
- LIMNOLOGY;
- 4914 Continental climate records;
- PALEOCEANOGRAPHY;
- 4954 Sea surface temperature;
- PALEOCEANOGRAPHY