HR: 14:50h
AN: GC53A-08    [Abstracts]
TI: A High-Resolution Biogenic Silica Record From Lake Titicaca, Peru-Bolivia: South American Millennial-Scale Climate Variability From 18-60 Kya
AU: * Ekdahl, E J
EM: eekdahl2@unl.edu
AF: Department of Geosciences, University of Nebraska-Lincoln, Lincoln, NE 68588 United States
AU: Fritz, S C
EM: sfritz2@unl.edu
AF: Department of Geosciences, University of Nebraska-Lincoln, Lincoln, NE 68588 United States
AU: Stevens, L R
EM: lstevens@unl.edu
AF: Department of Geosciences, University of Nebraska-Lincoln, Lincoln, NE 68588 United States
AU: Baker, P A
EM: pbaker@geo.duke.edu
AF: Division of Earth and Ocean Sciences, Duke University, Durham, NC 27708 United States
AU: Seltzer, G O
EM: goseltze@syr.edu
AF: Department of Earth Sciences, Syracuse University, Syracuse, NY 13244 United States
AB: Sediments recovered from a deep basin in Lake Titicaca, Peru-Boliva, were analyzed for biogenic silica (BSi) content by extraction of freeze dried sediments in 1% sodium carbonate. Sediments were dated using an age model developed from multiple $^{14}$C dates on bulk sediments. The BSi record shows distinct fluctuations in concentration and accumulation rate from 18 to 60 kya. Multi-taper method spectral analysis reveals a significant millennial-scale component to these fluctuations centered at 1370 years. High BSi accumulation rates correlate with enhanced benthic diatom preservation, suggesting that the BSi record is related to variations in lake water level. Modern-day Lake Titicaca lake level and precipitation are strongly related to northern equatorial Atlantic sea surface temperatures, with cooler SSTs related to wetter conditions. Subsequently, the spectral behavior of the GRIP ice core $\delta ^{18}$O record was investigated in order to estimate coherency and linkages between North Atlantic and tropical South American climate. GRIP data exhibit a significant 1370-year spectral peak which comprises approximately 26% of the total variability in the record. Despite a high degree of coherency between millennial-scale periodicities in Lake Titicaca BSi and GRIP $\delta ^{18}$O records, the Lake Titicaca silica record does not show longer term cooling cycles characteristic of D-O cycles found in the GRIP record. Rather, the Lake Titicaca record is highly periodic and more similar in nature to several Antarctic climate proxy records. These results suggest that while South American tropical climate varies in phase with North Atlantic climate, additional forcing mechanisms are manifest in the region which may include tropical Pacific and Southern Ocean variability.
DE: 9360 South America
DE: 4267 Paleoceanography
DE: 1845 Limnology
DE: 1615 Biogeochemical processes (4805)
DE: 1620 Climate dynamics (3309)
SC: Global Climate Change [GC]
MN: 2004 AGU Fall Meeting