Persistent El Niño-like conditions over the western Pacific during the Bølling–Allerød interstadial

Abstract Projecting El Niño-Southern Oscillation responses to future climate change are hindered by limited paleoclimate records spanning past abrupt climate transitions. This study combines multi-proxy records from the Northwest Borneo Trough over the past 30 kyr with transient climate simulations, reconstructing tropical western Pacific hydroclimate during Heinrich events and Bølling–Allerød warming. Results show contrasting responses: Heinrich events saw stronger winter monsoons bringing northern moisture for Borneo’s orographic rain, while Bølling–Allerød warming initiated central Pacific El Niño-like conditions tied to Northern Hemisphere ice-sheet retreat beyond a critical threshold and subsequently sustained by insolation minimum, combined with Southern Hemisphere forcing, leading to regional dryness/seasonal aridity. We demonstrate dual high-latitude controls on western Pacific variability during Dansgaard–Oeschger cycles: hemispheric thermal gradients and ice-sheet topography. These findings reveal the links between ice sheets, insolation, and western Pacific El Niño-like conditions, offering valuable insights into long-term El Niño-Southern Oscillation dynamics and future behavior.