Observed Changes in the Kuroshio Extension and Gulf Stream Based on Surface Drifter and OSCAR

A primary challenge in assessing ocean circulation changes remains the scarcity of in situ current observations. By integrating drifter-derived data with satellite-derived surface currents, this study provides the first direct observational characterization of surface current variability of the Kuroshio Extension (KE) and Gulf Stream (GS) from 1998 to 2023. The KE and the GS systems exhibit consistent decadal variability, with the signal amplitude surpassing their long-term trends during this period. The analysis suggests that North Atlantic Mid-latitude (NAM) sea surface temperature (SST) variations may, through associated atmospheric teleconnections, modulate wind stress curl field over the North Pacific subtropical gyre, and subsequently influence the intensity of the KE current strength. In contrast, GS variations are primarily driven directly by changes in the vertically integrated temperature and are nearly synchronous with local SST changes. In addition to intensity variations, both the KE and GS have undergone significant wind-driven poleward migrations, with the GS additionally experiencing a distinct onshore displacement. The main current axes exhibit more pronounced poleward shifts during periods of decadal velocity intensification (2011–2023). These findings strengthen our understanding of recent changes in surface currents and provide observational constraints for modeling the response of ocean circulation to climate change.