HR: 0800h
AN: PP31A-1516    [Abstracts]
TI: Western Tropical Pacific Convection and Temperature Since the Late Holocene Based on a High-Altitude Lacustrine Geochemical Record From New Guinea
AU: * Prentice, M L
EM: mike.prentice@unh.edu
AF: Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH 03824 United States
AU: Bates, M
EM: michael@pngtours.com
AF: Centre for Environmental Modeling and Prediction, University of New South Wales, Sydney, NSW 2033 Australia
AU: Dibb, J E
EM: jack.dibb@unh.edu
AF: Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH 03824 United States
AU: Clemens, S C
EM: Steven_Clemens@brown.edu
AF: Department of Geological Sciences, Brown University, Providence, RI 02924 United States
AB: We present the first inorganic carbonate (IC) and ostracod ¹⁸O and ¹³C records from a New Guinea lake and contend that they reflect past precipitation and convection in the western equatorial Pacific. The 1500 year record is from a 290 cm long core raised from Lake Gwam at 3530 m asl atop the Huon Peninsula of Papua New Guinea (6^oS, 147^oE). The 30 m deep,0.25 km² lake is a warm polymictic, reservoir-type lake. Varied climate data from the New Guinea highlands and free troposphere indicate monthly rainfall variations of 50% associated with ENSO, highs coincident with mature La Niñas. The core age model is based on ²¹⁰Pb, ¹⁴C dates, and tephrochronology. We developed a model for lake carbonate ¹⁸O that assumes a moderate amount effect on precipitation ¹⁸O. The model was driven over the last 50 years with a new compilation for highland P.N.G. rainfall and temperature. Model carbonate ¹⁸O chiefly reflect changes in precipitation ¹⁸O and amount and, secondarily, temperature change. Convergence between model and data is acceptable though the model underestimated observed IC ¹⁸O variability. The model yields a calibration between lake carbonate ¹⁸O and precipitation change. We attribute IC ¹³C variations that positively covary with IC ¹⁸O to productivity changes. Therefore, we suggest that IC ¹⁸O and ¹³C primarily reflect an open hydrologic system dominated by precipitation changes. From 1300 to 400 yrs BP, Lake Gwam IC ¹⁸O average ~3‰ more negative than average recent IC ¹⁸O. We infer that the climate was much wetter and warmer than at present, consistent with regional La Niña-like conditions. IC ¹⁸O show a depletion trend of 1‰ over this interval and exhibit short-term variability of >1‰. From 400 to 200 yrs BP, Lake Gwam IC ¹⁸O were 3‰ more positive than average recent IC ¹⁸O. This reflects a regional climate drier and colder than at present, consistent with reduced atmospheric convection relative to today and El Niño-like conditions.
DE: 0458 Limnology (1845, 4239, 4942)
DE: 1610 Atmosphere (0315, 0325)
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1854 Precipitation (3354)
DE: 3344 Paleoclimatology (0473, 4900)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005