Two flavors of north tropical Atlantic climate variability with distinct impact on Atlantic hurricanes

Variability of sea surface temperature (SST) in the north tropical Atlantic (NTA) exerts a substantial impact on Atlantic hurricane activity. Referred to as the NTA mode, its positive phase features warm SST anomalies, conducive to increased intensity and frequency of North Atlantic hurricanes. The period 2023-2024 saw two consecutive positive NTA events, featuring a broad warm anomaly pattern in 2024 following the 2023/24 strong El Niño, but a localized SST warm anomaly in the coastal region off northwest Africa in 2023 following a La Niña. Whether there exists inherent diversity in NTA dynamics and impact is unclear. Here we find that the NTA possesses two distinctive flavors: the basin-wide (BNTA) mode and coastal (CNTA) mode. Such diversity is underpinned by an asymmetric response of air-sea heat flux at the SST anomaly centers of the two NTA modes. The BNTA has an overall stronger impact on Atlantic hurricane activity due to its more westward and persistent warm anomaly pattern. Furthermore, since 1990s, the well-known impact from El Niño-Southern Oscillation on the north tropical Atlantic is felt through its influence on the BNTA mode. Our finding highlights the importance of distinguishing and understanding NTA flavors in assessing and predicting their climatic impacts.