Impact of the Atlantic Zonal Mode on Ocean Surface Waves in the Tropical Indo‐West Pacific During Boreal Summer

Abstract

Ocean surface waves, which are gravity waves primarily driven by surface winds, significantly influence air‐sea interactions, coastal ecology, and marine operations, among others. Tropical climate variability is shaped by ocean–atmosphere coupled modes such as the El Niño–Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD), which also influence ocean surface waves through changes in surface winds. This study examines the impact of the Atlantic Zonal Mode (AZM), a less‐studied climate driver, on the interannual variability of ocean surface waves in the tropical Indo‐West Pacific. A warm AZM induces surface wind anomalies that oppose the climatological winds. As a result, it reduces the wind sea by 0.2–0.3 m in the South China Sea (SCS) and by 0.1–0.2 m each in the Philippine Sea (PS) and the Bay of Bengal (BoB), and causes Southern Ocean swells to dominate by 0.1–0.2 m in the Arabian Sea. It is substantiated by consistent changes in the mean wave period and energy flux into waves. A warm AZM can favour marine operations in the SCS, PS, and BoB. On the contrary, a cold AZM is not observed to cause any statistically significant change in wave activity during the analysis period, highlighting an asymmetric impact of the AZM, the reasons for which require further investigation using wave model sensitivity experiments. Given the future projections of a weakening Atlantic cold tongue under global warming, the effects of warm AZM events may intensify, potentially leading to further reductions in tropical Indo‐West Pacific wave activity. These findings highlight the importance of incorporating AZM impacts in wave climate assessments.

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