ENSO's Imprint on the Southern Ocean: Wind Waves Drive Surface Cross-Frontal Flow

Abstract

Tropical teleconnection associated with El Niño–Southern Oscillation (ENSO) is widely recognized for regulating multiple physical processes in the Southern Ocean. However, despite its influence on Southern Ocean wind patterns, the response of surface flow has received little attention. Here, we investigate surface flow in the Southern Ocean using surface-drifting buoy trajectories collected during September 2022–May 2023 and November 2023–June 2024. Drifter observations exhibit significant cross-frontal movements primarily driven by Stokes drift rather than Ekman velocity. The observations also show interannual variability, with strong poleward cross-frontal flow in 2024 during a strong El Niño event. Further analyses over the past approximately 31 years indicate that ENSO teleconnection is the primary driver of this interannual variability. These findings provide a new perspective on how tropical teleconnection influences cross-frontal flow via wind waves and highlight their potential role in tracer transport across fronts.