Trans-basin linkages prolong Northwestern Pacific marine heatwaves through a circumglobal wave pattern.

Abstract

Marine heatwaves in the Northwestern Pacific (NWP) have become increasingly frequent and persistent, yet the mechanisms enabling their multiseasonal duration remain poorly understood. Through observational analyses and climate model experiments, we demonstrate that NWP marine heatwaves are primarily driven by a quasistationary wavenumber 5 circumglobal wave (CGW) pattern that operates independently of El Niño-Southern Oscillation. The CGW modulates surface heat fluxes during summer, triggering a self-reinforcing feedback loop where NWP warming intensifies the CGW pattern, amplifying and prolonging heatwaves across extended warm seasons. Additionally, CGW-driven summer warming in the northern North Atlantic persists into winter through oceanic thermal inertia, exciting a great-circle wave pattern that propagates back to the NWP, sustaining heatwaves through cold seasons. This interplay between atmospheric waves and trans-basin interactions enables multiyear marine heatwave events. Analysis of observational data and climate model simulations reveals a strengthening CGW influence in recent decades, indicating more frequent and prolonged NWP marine heatwaves under ongoing global warming.