21-2 A High-Resolution Integrated Approach to Reconstructing Kuroshio Current Extension Variability: Foraminiferal Assemblages and Stable Isotopes

Session: Insights from Microfossils and Their Modern Analogs: From Traditional to Emerging Approaches

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Under anthropogenic climate change, subtropical western boundary currents are warming at a rate of 2–3 times faster than other parts of the world ocean. These currents transport warm equatorial waters northward, providing heat, salt, nutrients, and gases to the mid-latitudes. The long-term behavior of WBCs is obscured by the natural decadal modulation of the currents, but understanding how WBCs will continue to change under increased warming is imperative. To further our understanding of WBCs, we can utilize deep-sea sediment records across key climate intervals that are analogues for today and future warming scenarios. The mid-Piacenzian Warm Period (mPWP; ~3.0–3.3 Ma) is one such interval as it contained atmospheric CO₂ levels and globally averaged temperatures similar to today. The Kuroshio Current Extension (KCE) is the subtropical WBC in the northwest Pacific Ocean and from observational data, has warmed by 1–2°C over the last 100 years. Prior stable isotopic analyses conducted at one deep-sea site on the northern edge of the KCE (Ocean Drilling Program Hole 1207A) from Marine Isotope Stage (MIS) M2 to KM5c indicated the current warmed by 1.3–1.9°C, indicating that KCE has reached the warming today as it did during the mPWP. However, this finding is from one site, and previous stable isotopic analyses across the mPWP from the KCE region were of low (~14 kyr) resolution, limiting insight into this dynamic region. This study improves upon past work by creating high-resolution (~3 kyr) planktic foraminiferal δ¹⁸O and δ¹³C stable isotopic analyses at ODP Holes 1208A and 1209A, located south of Hole 1207A and within the core of the KCE, respectively. These data will be used to infer past temperature/salinity and productivity changes through the study interval, and will be compared to the geochemical record of Hole 1207A. Additional insight into the KCE’s behavior will be gained by X-ray fluorescence (XRF) data at both Holes 1208A and 1209A. By resolving fine-scale variability, the study identifies whether warming at Holes 1208A and 1209A was localized or regional, improving understanding of KCE dynamics—critical for predicting modern and future ocean circulation and climate trends.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-6709

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