A transient rise in tropical sea surface temperature during the Paleocene-Eocene Thermal Maximum

The Paleocene-Eocene Thermal Maximum (PETM) has been attributed to a rapid rise in greenhouse gas levels. If so, warming should have occurred at all latitudes, although amplified toward the poles. Existing records reveal an increase in high-latitude sea surface temperatures (SSTs) (8degrees to 10 degreesC) and in bottom water temperatures (4degrees to 5 degreesC). To date, however, the character of the tropical SST response during this event remains unconstrained. Here we address this deficiency by using paired oxygen isotope and minor element (magnesium/calcium) ratios of planktonic foraminifera from a tropical Pacific core to estimate changes in SST. Using mixed-layer foraminifera, we found that the combined proxies imply a 4degrees to 5 degreesC rise in Pacific SST during the PETM. These results would necessitate a rise in atmospheric pCO(2) to levels three to four times as high as those estimated for the late Paleocene.