Seasonal phase change of the North Atlantic Tripole Sea surface temperature predicted by air-sea coupling

Abstract

The North Atlantic Tripole sea surface temperature anomaly (NAT SSTA) is critical for predicting climate in Eurasia. Predictions for summer climate anomalies currently assume the NAT SSTA phase persists from boreal winter through summer. When NAT phase switches, predictions become unreliable. However, the NAT phase sustained/reversal mechanism from boreal winter to spring remains unclear. This study demonstrates that the evolution of the NAT phase could be driven by the North Atlantic Oscillation (NAO). When NAO phase persists (switches) during preceding boreal winter, the NAO-driven wind anomalies favor maintenance (transition) of NAT phase by causing sea surface heat flux anomalies. Meanwhile, NAT SSTA causes eddy-mean flow interaction by increasing atmospheric baroclinity, thereby generating positive feedback on the former NAO phase. The NAO phase change is leading 1–3 months for the NAT phase. These findings deepen our understanding of the interaction between NAO and NAT and provide implications for seasonal prediction in Eurasia.