As mafic weathering in the tropics is still a matter of debate as to whether it drove or negatively fed back the late Cenozoic global cooling, quantifying the variation of weathering flux is the key to solve this conundrum. Here, we present the ratio of meteoric cosmogenic ¹⁰Be to continent-weathered ⁹Be in marine sediemnts from the Sulu Sea in Southeast Asia. In contrast to previous near‑constant marine ¹⁰Be/⁹Be records, our results reveal a two‑fold increase in ¹⁰Be/⁹Be ratios over the past 8 million years, indicating a continuous decrease of weathering flux in Southeast Asia. Our results chanllenge the hypothesis of global weathering stability during late Cenozoic cooling. Combined with previouly proposed ~4 °C decresase of the Western Pacific Warm Pool at this timeperiod, we determined an Arrhenius activation energy of 135 ± 38 kJ/mol. This value is slightly higher than those observed in laboratory and natural systems, attributed to the warm and high precipitation climate in Southeast Asia. These findings suggest that temperature‑dependent weathering of island basalt in the tropics contributed to maintaining the atmospheric CO₂ budget as a negative feedback to global cooling throughout the late Cenozoic.
 

10Be/9Be,Global cooling,Basalt weathering,Negative feedback