CO2‐Induced Decoupling of Tropical Surface and Thermocline Water Temperature at the Onset of Interglacials

Abstract

AbstractTropical air‐sea interaction is important in global climate change; its behavior over geological history is poorly understood but can be explored by examining reconstructed sea surface temperature (SST) and thermocline water temperature (TWT). Here, deglacial‐interglacial air‐sea interactions over the past 500 ka were studied by comparing UK'37‐derived SST0‐30m and TEXH86‐derived TWT75m in a sediment core from the southern South China Sea. During deglacials, SST0‐30m and TWT75m varied synchronously toward interglacial peaks, while during the peak interglacials, TWT75m decreased earlier than SST0‐30m. These changes have been found ubiquitously in tropical oceans during the last two glacial‐interglacial cycles. We propose that the prolonged warm interglacial SST was probably sustained by the natural CO2 “overshoot” greenhouse effect at the end of most terminations. The early interglacial TWT decrease following local insolation is driven by the decreasing downward heat transport efficiency induced by weakening wind stirring.