Sea surface temperature differences between the Western equatorial Pacific and Northern South China Sea since the Pliocene and their paleoclimatic implications

Alkenone sea surface temperatures (SSTs) in the northern South China Sea (SCS) were reconstructed for the last similar to 3.8 Ma. The SST difference between the western equatorial Pacific and northern SCS was then estimated, showing a general increase since similar to 2.8 Ma. Three features of the SST-gradient evolution were prominent: 1) low values (<2 degrees C) in the late Pliocene; 2) increased values during the late Pliocene/early Pleistocene (from 1 to 4 degrees C); and 3) high values (similar to 4 degrees C) by the end of the early Pleistocene. These features were also shown in zonal SST gradient across equatorial Pacific, implying an intimate relationship of the meridional Hadley and East Asian monsoon circulations with the zonal Walker circulation. Moreover, the SST gradient records displayed some characters unique to the equatorial Pacific and not found in benthic delta O-18 record, suggesting that zonal tropical climate change could spread into higher latitude by interactions with meridional circulations.