Pliocene-Pleistocene pCO2 Changes Based on Alkenone Carbon Isotopes
Abstract
Climate change over the last 5 Myr includes the transition from the early Pliocene warm period to the ice age climate of the late Pliocene and Pleistocene. A moderate decrease in pCO2 is one of the many proposed causes. Here we reconstruct pCO2 changes using records of the total carbon isotopic fractionation that occurs during algal photosynthesis for the past 5 Myrs to test the overarching hypothesis that the pattern of warming during the early Pliocene warm period, as well as the subsequent cooling, was forced by a corresponding increase and decrease in pCO2. Our approach is to extract and determine the carbon isotopic value of haptophyte-derived long- chain ketone biomarkers (alkenones) from a globally dispersed set of DSDP/ODP cores. Our preliminary data from tropical and subtropical sites suggest that pCO2 during the Pliocene warm period was ~80 ppm (30%) higher than the pre-industrial level, with much of the pCO2 drop occurring prior to ~2 Ma. Reconstructions of pCO2 changes from globally distributed sites will be presented.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2007
- Bibcode:
- 2007AGUFMPP43B1272L
- Keywords:
-
- 1055 Organic and biogenic geochemistry;
- 4850 Marine organic chemistry (0470;
- 1050);
- 4912 Biogeochemical cycles;
- processes;
- and modeling (0412;
- 0414;
- 0793;
- 1615;
- 4805);
- 4930 Greenhouse gases