Reconstruction of bottom water ventilation changes in the West Philippine Sea during the last glacial-interglacial period

Abstract

Abstract Global deep-water circulation plays a crucial role in regulating long-term carbon storage in both the ocean and atmosphere. During the last glacial period, it is reported that this circulation slowed down, causing glacial intermediate water to descend to depths of 2,000 m in the Pacific. This process is thought to be a key mechanism in restricting global deep-water circulation and reducing atmospheric carbon dioxide concentrations during glacial periods. Conversely, the emergence of a potential deep-water formation zone in the northwestern Pacific during deglaciation adds complexity to these circulation patterns. Addressing the scarcity of sedimentary records in the subtropical western Pacific for paleoceanographic reconstruction, sediment core YK15-01 PC13 (23.5°N, 124.24°E; southeast of Ishigaki Island at a depth of 2,520 m) used in this study, collected in 2015. By analyzing coexisting planktonic and benthic foraminifera, we have reconstructed radiocarbon ventilation ages in this region since the last glacial maximum. Our findings, including ventilation age records compiled from the Atlantic and Pacific Oceans, reveal opposing deep-water circulation patterns from the last glacial to the interglacial period, including during the Heinrich Event 1 (HE1) and Younger Dryas (YD). This supports the theory of a seesaw-like oscillation in ocean circulation. Furthermore, the improved ventilation observed during HE1 and YD suggests a contribution from deep water formed in the high-latitude Pacific, influenced by cooler climate conditions. This glacial North Pacific deep water, likely confined to the northwestern Pacific, has left its mark in the subtropical western Pacific records. This research enhances our understanding of deep-water circulation interactions between the Atlantic and Pacific and contributes new insights into the role of northern Pacific deep water in influencing atmospheric carbon dioxide variations during the last deglaciation.

Keywords

• Deep-water circulation
• Intermediate water
• Ventilation
• Radiocarbon ages
• Glacial period