Early Palaeogene temperature evolution of the southwest Pacific Ocean
Abstract
Relative to the present day, meridional temperature gradients in the Early Eocene age (~56-53Myr ago) were unusually low, with slightly warmer equatorial regions but with much warmer subtropical Arctic and mid-latitude climates. By the end of the Eocene epoch (~34Myr ago), the first major Antarctic ice sheets had appeared, suggesting that major cooling had taken place. Yet the global transition into this icehouse climate remains poorly constrained, as only a few temperature records are available portraying the Cenozoic climatic evolution of the high southern latitudes. Here we present a uniquely continuous and chronostratigraphically well-calibrated TEX86 record of sea surface temperature (SST) from an ocean sediment core in the East Tasman Plateau (palaeolatitude ~65°S). We show that southwest Pacific SSTs rose above present-day tropical values (to ~34°C) during the Early Eocene age (~53Myr ago) and had gradually decreased to about 21°C by the early Late Eocene age (~36Myr ago). Our results imply that there was almost no latitudinal SST gradient between subequatorial and subpolar regions during the Early Eocene age (55-50Myr ago). Thereafter, the latitudinal gradient markedly increased. In theory, if Eocene cooling was largely driven by a decrease in atmospheric greenhouse gas concentration, additional processes are required to explain the relative stability of tropical SSTs given that there was more significant cooling at higher latitudes.
- Publication:
-
Nature
- Pub Date:
- October 2009
- DOI:
- 10.1038/nature08399
- Bibcode:
- 2009Natur.461..776B