Pliocene Sea Surfaces Temperature High in Tropical Warm Pools

Australia: The Land Where Time Began

Pliocene Sea Surfaces Temperature High in Tropical Warm Pools

In the Atlantic and Pacific oceans the western warm pools are a critical source of heat and moisture for the tropical climate system. The global mean temperatures have cooled 3-4^oC over the past 5 My, though present reconstructions of sea surface temperatures have indicated that the warm pools remained at stable temperatures over that period of time. It has been suggested, based on this stability, that a thermostat-like mechanism has maintained consistent tropical sea surface temperatures. In this study (O’Brien et al.,)¹ the reconstructed sea surface temperatures in the South China Sea, Caribbean Sea and western equatorial Pacific Ocean for the past 5 My by the use of a combination of Mg/Ca-, TEX₈₆^H- and U^k’/₂₇- proxies for surface temperatures. It was indicated by their data that from about 5 to 2.5 Ma, over the period of the Pliocene warmth, the warm pools in the western Atlantic and western Pacific were about 2^oC warmer that the present temperatures of those warm pools. Based on these results O’Brien et al.,¹ suggest that the apparent lack of warmth indicated by the previous studies was an artefact of low seawater Mg/Ca ratios in the oceans during the Pliocene. When this bias is accounted for the data resulting from the present study the sea surface temperatures did actually change in conjunction with global mean temperatures, leading to the conclusion that in the equatorial oceans of the Pliocene the temperature of the warm pools was not limited by a thermostat-like mechanism.