Local hydroclimate alters interpretation of speleothem δ 18 O records

Oxygen isotopes (δ O) are the most commonly utilized speleothem proxy and have provided many foundational records of paleoclimate. Thus, understanding processes affecting speleothem δ O is crucial. Yet, prior calcite precipitation (PCP), a process driven by local hydrology, is a widely ignored control of speleothem δ O. Here we investigate the effects of PCP on a stalagmite δ O record from central Vietnam, spanning 45 - 4 ka. We employ a geochemical model that utilizes speleothem Mg/Ca and cave monitoring data to correct the δ O record for PCP effects. The resulting record exhibits improved agreement with regional speleothem δ O records and climate model simulations, suggesting that the corrected record more accurately reflects precipitation δ O (δ O ). Without considering PCP, our interpretations of the δ O record would have been misleading. To avoid misinterpretations of speleothem δ O, our results emphasize the necessity of considering PCP as a significant driver of speleothem δ O.