Characterising Permanent El Nino v. La Nina-Like States in the Pliocene: a Multi-Proxy Approach.
Abstract
The warm Early Pliocene period 5 to 3 Myr BP represents the closest analogue to future climates on the palaeo-records. Although parameters such as solar insolation, continental configuration and atmospheric CO2 concentrations were similar to today, global temperatures were significantly warmer and northern hemisphere glaciation did not begin until a shift in the global climate regime at ~3 Myr BP. Tropical climate during the period of Pliocene warmth has been proposed to be a permanent El Nino-like regime with palaeo-sea surface temperature (SST) reconstructions predicting no equatorial Pacific temperature gradient until 3 Myr BP (Wara et al., 2005). However, an alternative scenario, i.e. permanent La Nina-like conditions, was proposed by Rickaby and Halloran (2005) who, using an apparently more rigorous approach to sample preparation for Mg/Ca analysis, reconstructed cooler eastern equatorial Pacific (EEP) SST and an equatorial SST gradient similar to today through the warm Pliocene period. While a permanent El Nino-like state may be the favoured scenario, potentially contributed to elevated global temperatures of this period relative to today, reliable palaeo-records are fundamental to reconstructing the true climatic regime during this period. We propose a multi-proxy approach to assessing surface ocean temperature, structure and productivity in the EEP. We present preliminary Mg/CaG. ruber-based SST records from ODP hole 667A in the Panama Basin for the period 2 to 1.7 Myr. These records are coupled with previously published δ18OG. ruber from the same site and compared with diatom-inferred SST and radiolarian productivity records. Successful reconstruction of EEP climate and oceanic state will be extended back to 6 Myr with a complete array of proxy records to include foraminiferal assemblage and alkenone derived SST records and Cd/Ca productivity indicator.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2006
- Bibcode:
- 2006AGUFMPP13B1592P
- Keywords:
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- 1050 Marine geochemistry (4835;
- 4845;
- 4850);
- 1065 Major and trace element geochemistry;
- 1616 Climate variability (1635;
- 3305;
- 3309;
- 4215;
- 4513);
- 4279 Upwelling and convergences (4964);
- 4522 ENSO (4922)