Understanding the Complicated Relationship Between ENSO and Wintertime North Tropical Atlantic SST Variability

The El Nino-Southern Oscillation (ENSO) is known to influence the North Tropical Atlantic (NTA) sea surface temperature (SST) during its decaying spring, providing an essential source of NTA predictability. However, the positive ENSO-NTA SST relationship is absent during boreal winter, impeding accurate anticipation of wintertime NTA SST fluctuations. We find that this absence is mainly due to different NTA preconditions. Taking into account the previous summer NTA SST state as an initial condition, a robust relationship is established between ENSO and wintertime NTA SST variability. Furthermore, we show that the NTA initial conditions are in part traced to the ENSO preconditions. Besides, the simultaneous local atmospheric conditions play a role in shaping the initial NTA SST variabilities, especially in the developing summer of El Nino events. The understanding of the complicated ENSO-wintertime NTA SST relationship has implications for exploring trans-basin climate interactions and associated climate predictability. Plain Language Summary One of the most striking features of the North Tropical Atlantic (NTA) sea surface temperature (SST) variability is its pronounced dependency on the El Nino-Southern Oscillation (ENSO). The ENSO remote effects are felt in the NTA SST a few months after the mature phase. However, an absence of statistically significant linkage between wintertime NTA SST anomalies and ENSO largely limits our understanding of the wintertime climatic variations over the NTA sector. In this study, we show that a robust positive linkage exists between ENSO and NTA SST variability during winter in light of the NTA SST tendency, and the previous summer NTA SST state as an initial condition acts to explain the complicated ENSO-wintertime NTA SST relationship. We also discuss about the possible dynamical origins of the NTA initial conditions, which are attributable to the preceding ENSO conditions as well as the simultaneous local atmospheric conditions.

Automated summary

The El Nino-Southern Oscillation (ENSO) has a robust relationship with North Tropical Atlantic (NTA) sea surface temperature (SST) variability during winter, when previous summer NTA SST conditions are taken into account. The absence of this relationship during winter is mainly due to different NTA preconditions. Understanding the complicated ENSO-wintertime NTA SST relationship has implications for climate predictability.