NOAA/WDS Paleoclimatology - Plio-Pleistocene Tropical Alkenone SST Reconstructions

Determining the timing and amplitude of tropical sea surface
temperature (SST) change is an important part of solving the
puzzle of the Plio-Pleistocene ice ages. Alkenone-based tropical
SST records from the major ocean basins show coherent glacial-
interglacial temperature changes of 1° to 3°C that align with
(but slightly lead) global changes in ice volume and deep ocean
temperature over the past 3.5 million years. Tropical temperatures
became tightly coupled with benthic d18O and orbital forcing
after 2.7 million years. We interpret the similarity of tropical
SST changes, in dynamically dissimilar regions, to reflect "top-down"
forcing through the atmosphere. The inception of a strong carbon
dioxide-greenhouse gas feedback and amplification of orbital forcing
at ~2.7 million years ago connected the fate of Northern Hemisphere
ice sheets with global ocean temperatures since that time.