Tropical response to the 8200 yr B.P. cold event? Speleothem isotopes indicate a weakened early Holocene monsoon in Costa Rica
- Matthew S. Lachniet*1,
- Yemane Asmerom*2,
- Stephen J. Burns*3,
- William P. Patterson*4,
- Victor J. Polyak*5 and
- Geoffrey O. Seltzer*6
- 1Department of Geoscience, MS-4010, University of Nevada, Las Vegas, Nevada 89154, USA
- 2Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131, USA
- 3Department of Geosciences, University of Massachusetts, Amherst, Massachusetts 01003-9297, USA
- 4Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2, Canada
- 5Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131, USA
- 6Department of Earth Sciences, 204 Heroy Geology Laboratory, Syracuse University, Syracuse, New York 13244, USA
Abstract
A δ18O monsoon rainfall proxy record from a U-Th–dated Costa Rican stalagmite (8840–4920 yr B.P.) documents an early Holocene dry period correlative with the high-latitude 8200 yr B.P. cold event. High δ18O values between ca. 8300 and 8000 yr B.P. demonstrate reduced rainfall and a weaker monsoon in Central America. A relatively wetter and more stable monsoon was established ca. 7600 yr B.P. The early Holocene dry event suggests a tropical-extratropical teleconnection to the 8200 yr B.P. cold event and a possible association of isthmian rainfall anomalies with high-latitude climate changes. The likely source of such a tropical anomaly is a decrease in Atlantic thermohaline circulation and atmospheric perturbations associated with drainage of proglacial lakes and freshwater discharge into the North Atlantic. A weaker monsoon at 8200 yr B.P. may be linked to wetland contraction and a decrease in methane observed in Greenland ice cores.
- Costa Rica
- tropics
- paleoclimate
- 8200 yr B.P. event
- stalagmite
- δ18O
- Holocene
- Central American monsoon
- Intertropical Convergence Zone
- U-Th dating
Footnotes
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↵*Corresponding author matthew.lachnietccmail.nevada.edu. The coauthors contributed equally to this project
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- Accepted July 14, 2004.
- Received May 6, 2004.
- Revision received July 14, 2004.
- Geological Society of America
