Observational evidence for a delayed Gulf Stream – Kuroshio Extension linkage via the Northern Hemisphere atmospheric bridge (1980–2024) — evaluation of the Yamagami mechanism

This study provides observational evidence for a delayed influence of Gulf Stream (GS) sea surface temperature (SST) variability on the Kuroshio Extension (KE) during 1980–2024, motivated by the atmospheric-bridge mechanism proposed by Yamagami et al. (2025). Using multiple SST records and atmospheric reanalysis data, lag-correlation analyses reveal a robust GS-leading relationship with the KE, characterized by a dominant low-frequency response emerging at multi-year delays of approximately 24–36 months. This delayed signal persists across a wide range of statistical treatments, including detrending, ENSO removal, autoregressive prewhitening, band-pass filtering, and jackknife resampling, and exceeds significance thresholds derived from autocorrelated noise models.