HR: 08:15h
AN: PP11C-02 INVITED     [Abstracts]
TI: Speleothem Paleorainfall Records from the Isthmus of Panama: Tropical Forcing or Response to the Extratropics?
AU: * Lachniet, M S
EM: matthew.lachniet@ccmail.nevada.edu
AF: University of Nevada Las Vegas, 4505 Maryland Parkway Department of Geoscience, Box 4010 , Las Vegas, NV 89154 United States
AU: Asmerom, Y
EM: asmerom@unm.edu
AF: University of New Mexico, Department of Earth and Planetary Sciences 200 Yale Boulevard NE, Albuquerque, NM 87131 United States
AU: Burns, S
EM: sburns@geo.umass.edu
AF: University of Massachusetts, 611 North Pleasant St. Department of Geosciences 233 Morrill Science Center, Amherst, MA 01003 United States
AU: Polyak, V
EM: polyak@unm.edu
AF: University of New Mexico, Department of Earth and Planetary Sciences 200 Yale Boulevard NE, Albuquerque, NM 87131 United States
AU: Burt, L
EM: burtl3@unlv.nevada.edu
AF: University of Nevada Las Vegas, 4505 Maryland Parkway Department of Geoscience, Box 4010 , Las Vegas, NV 89154 United States
AU: Azouz, A
EM: azouza@unlv.nevada.edu
AF: University of Nevada Las Vegas, 4505 Maryland Parkway Department of Geoscience, Box 4010 , Las Vegas, NV 89154 United States
AB: Evidence from oxygen isotope time series of U-series-dated stalagmites from the Isthmus of Panama reveal both a tropical link to extratropical climate change, and variability related to tropical climate processes. Large oceanographic circulation changes in the North Atlantic appear to have affected the strength of the Central American Monsoon over the Caribbean coast of Costa Rica at 10°N latitude during the early Holocene. Similarly, a marine isotope stage 3 stalagmite record from Pacific coastal Costa Rica (36.2 to 29.6 ka) reveals millennial-scale climate oscillations which we correlate to Dansgaard/Oeschger events in the North Atlantic and Greenland. During the mid to late Holocene, δ¹⁸O variability, in contrast, appears to be controlled by internal tropical ocean forcing, most likely attributed to the El Ni¤o/Southern Oscillation (ENSO). We see no strong evidence for a shift in mean δ¹⁸O values in the mid to early Holocene associated with a postulated shift in ENSO variability from other tropical American records. We infer that ENSO, as manifested in eastern Pacific Intertropical Convergence Zone rainfall, remained relatively constant since ca. 8 ka to present. Average δ¹⁸O values and variability during MIS3 and the Holocene are similar, suggesting that isthmian rainfall during these times was approximately equal. We conclude that tropical ITCZ rainfall on the Isthmus responded to nearly equal degrees to extratropical (D/O-type events) and tropical (ENSO) forcing. Although our temporal coverage is thus far limited, we see no evidence for δ¹⁸O variation on precessional time scales, such as observed in other tropical monsoon systems, suggesting that solar insolation is not a dominant control on isthmian rainfall, at least for the periods covered by our stalagmite records. Additional stalagmite records from the late Holocene to ca. 90 ka are being developed from Pacific coastal Costa Rican and Mexican stalagmites, which will help answer remaining questions about tropical rainfall variability over the late Quaternary.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1620 Climate dynamics (0429, 3309)
DE: 1655 Water cycles (1836)
DE: 4922 El Nino (4522)
DE: 4958 Speleothems
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005