Abrupt ENSO changes over the last 15,000 years; inferences from Peru margin organic biomarker records

Author(s): Makou, M. C.; Eglinton, T. I.; Oppo, D. W.; Hughen, K. A.
Author Affiliation(s): Primary:
Rutgers University, New Brunswick, NJ, United States
Other:
Woods Hole Oceanographic Institution, United States
Volume Title: AGU 2006 fall meeting
Source: Eos, Transactions, American Geophysical Union, 87( Fall Meeting Suppl.); American Geophysical Union 2006 fall meeting, San Francisco, CA, Dec. 11-15, 2006. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0096-3941 CODEN: EOSTAJ
Note: In English
Summary: Multi-molecular stratigraphic records developed from Peru Margin sediments (ODP Site 1228D; 11°S, 252 m) provide information about changes in upwelling and ENSO variability over the last 15 ka. Parallel records of molecular marker lipids derived from algal, bacterial, and terrestrial vascular plant sources were generated via gas chromatography coupled with time-of-flight mass spectrometry, which enables facile yet thorough investigation of the multiple lines of information embedded in the organic sedimentary record. The study site is located within the eastern tropical Pacific upwelling zone, and is thus well situated to directly monitor changes in El Niño strength over time. Factor analysis provided the means to identify distinct modes of variability within the broad array of biomarker records generated, and was employed to identify target compounds that could be used to investigate changes in environmental variables. In particular, dinosterol and cholesterol were used to infer changes in El Niño and La Niña strength, respectively, through the effects of these climate phenomena on productivity and upwelling. The dinosterol record suggests reduced El Niño strength from 12.9 to about 6.5 ka (pending age verification), at which point it increased abruptly, marking the resurgence of robust El Niño conditions in the Holocene. The remainder of the record from the 6.5 ka abrupt transition to the present was punctuated by further high-amplitude variability. The cholesterol abundance record varies in parallel with that of dinosterol, suggesting stronger (weaker) regional upwelling during periods of enhanced (reduced) El Niño conditions, consistent with a concurrent increase (decrease) in La Niña strength. The paired biomarker records imply that El Niño and La Niña varied in concert over the last 15 ka, rather than acting as shifting end-member states of tropical Pacific climate. By this hypothesis, ENSO variability as a whole was moderately enhanced in the early part of the record, weak from 12.9 to 6.5 ka, and strong but highly variable from 6.5 ka onward. Similarities between Peru Margin biomarker records and South American and eastern Atlantic climate records suggest abrupt, far-reaching changes in tropical climate that are related to ENSO and likely propagated through atmospheric connections.
Year of Publication: 2006
Research Program: ODP Ocean Drilling Program
Key Words: 24 Surficial Geology, Quaternary Geology; Alcohols; Atmosphere; Biomarkers; Cenozoic; Climate change; Continental margin sedimentation; Cores; East Pacific; El Nino; El Nino Southern Oscillation; Equatorial Pacific; Holocene; Leg 201; Marine sediments; ODP Site 1228; Ocean Drilling Program; Organic compounds; Pacific Ocean; Paleo-oceanography; Paleocirculation; Paleoclimatology; Peru; Quaternary; Sedimentation; Sediments; South America; South Pacific; Southeast Pacific; Steroids; Sterols; Tropical environment; Upper Quaternary; Upwelling
Coordinates: S110400 S110400 W0780500 W0780500
Record ID: 2007080015
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