Enhanced Teleconnection Between El Niño and Northern South China Sea Shelf Winter SST During Positive Atlantic Multidecadal Oscillation

Why It Matters

Understanding the AMO’s modulation of El Niño impacts improves seasonal SST forecasts for a region critical to fisheries, tourism, and coastal economies, enhancing climate risk management across East Asia.

Key Takeaways

• Positive AMO amplifies El Niño influence on NSCS winter SST
• Westward‑shifted El Niño core strengthens western North Pacific anticyclone
• Weakened NSCS cyclonic gyre enables warm boundary‑layer advection
• Empirical model using Niño indices boosts NSCS winter SST forecasts
• Findings aid regional climate prediction and socioeconomic planning

Pulse Analysis

The northern South China Sea shelf is a climate‑sensitive zone where winter sea surface temperatures dictate marine productivity, fisheries yields, and coastal livelihoods. While El Niño events traditionally raise SSTs in this area, the magnitude of that response has long puzzled scientists, showing pronounced swings over several decades. Recent analyses combining satellite observations and reanalysis data reveal that the Atlantic Multidecadal Oscillation—a long‑term fluctuation of North Atlantic sea temperatures—acts as a master switch, toggling the strength of the El Niño‑NSCS teleconnection.

During a positive AMO phase, enhanced convection over the North Atlantic reshapes atmospheric wave patterns that travel into the tropical Pacific. This process steepens the Pacific’s zonal SST gradient, nudging the warm pool of an El Niño event westward. The displaced anomaly spawns a more robust western North Pacific anticyclone, which in turn suppresses the cyclonic gyre that normally circulates cooler waters around the NSCS. The resulting wind‑driven warm advection along the western boundary becomes the primary driver of the observed SST surge on the shelf, a mechanism that was previously underappreciated.

Capitalizing on this mechanistic insight, the authors built an empirical forecast model that selects appropriate Niño indices based on the prevailing AMO phase. The model delivers a marked improvement in winter SST prediction skill for the NSCS, offering stakeholders—ranging from fishery managers to disaster planners—a more reliable tool for anticipating temperature‑driven ecosystem changes. Beyond regional benefits, the study underscores the importance of cross‑basin climate interactions, suggesting that long‑term Atlantic variability should be a standard component of Pacific‑Asian climate outlooks.