From Greenhouse to Icehouse: Evidence for Late Early Eocene Concomitant Cooling of Southern Ocean Surface Waters and Global Deep Waters From Dinoflagellate Endemism
Abstract
ODP Leg 189 drilling around Tasmania retrieved continuous Eocene records from the Southern Ocean - Antarctic Margin. The shallow marine, pro-deltaic successions of Sites 1170, 1171 and 1172 include the interval representing the onset (55 Ma) and termination (50 Ma) of the Early Eocene Climatic Optimum (EECO). The end of the EECO is globally reflected in the oceans by the onset of increasingly cooler deep-water temperatures, and marks the onset of the trend towards the Icehouse world. Here we show that a strong increase of endemic Antarctic dinoflagellates precisely matches the termination of the EECO in the Southern (Pacific) Ocean. The record of these surface-dwelling organisms thus indicates that changes of surface water parameters, notably temperature, occurred near simultaneously with global deep-water temperature changes. Moreover, the signal coincides with the return to heavier d13C-values, and atmospheric CO2 decline. Comparison of the field data with predictions from fully coupled climate model simulations, and a new basic understanding of Eocene Southern Ocean circulation, suggests that changes in carbon burial was driving changes in atmospheric greenhouse gasses, and the apparently coupled surface- and deep-water temperature signals.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2004
- Bibcode:
- 2004AGUFMPP54B..04B
- Keywords:
-
- 4805 Biogeochemical cycles (1615);
- 4870 Stable isotopes;
- 3030 Micropaleontology;
- 1635 Oceans (4203);
- 0325 Evolution of the atmosphere