Early Pliocene climate: A perspective from the western equatorial Atlantic warm pool

High-resolution (similar to 3-4 kyr) planktonic stable isotope stratigraphies from Site 925 drilled on Ceara Rise (Ocean Drilling Program Leg 154) are used to investigate the role of the western equatorial Atlantic sea surface hydrography in early Pliocene (3.2-4.7 Ma) climate change. Oxygen isotope results from Globigerinoides sacculifer, a mixed layer dweller, suggest that equatorial sea surface temperatures were cooler than today by similar to 2 degrees-3 degrees C, consistent with relatively strong northward advection of heat away from the equator. Oxygen isotope results from Neogloboquadrina dutertrei suggest that over the long term this thermocline dweller tracks global ice volume fluctuations. Stable isotope gradients between the two planktonic species throughout the entire interval imply a stable warm pool in the western equatorial Atlantic, We observe a rapid (3.4 kyr) decrease in G, sacculifer and the N, dutertrei delta(18)O values at 4.36 Ma that may reflect a freshening of the sea surface, a direct response to a southward displacement of the Intertropical Convergence Zone, and perhaps, an indirect response to restricted flow through the Central American Seaway.