Can Ningaloo Niño/Niña Develop Without El Niño–Southern Oscillation?

Ningaloo Nino/Nina is the dominant climate mode in the southeastern Indian Ocean with its center of positive/negative sea surface temperature anomalies attached to Australia. Ningaloo Nino is the major cause of marine heatwaves in the region. Although oceanic variability in this region has long been considered mainly as a response to the El Nino–Southern Oscillation (ENSO), some recent studies have suggested the possible existence of local air‐sea feedback processes. Using a state‐of‐the‐art ocean‐atmosphere coupled model that realistically simulates Ningaloo Nino/Nina, whether Ningaloo Nino/Nina can occur independently of ENSO is examined. Even in an experiment in which ENSO is suppressed by strongly nudging tropical Pacific sea surface temperatures toward the model climatology, Ningaloo Nino/Nina with a similar magnitude and seasonality still develops, likely through an air‐sea interaction off Western Australia amplifying atmospheric stochastic forcing. This study is the first to show that Ningaloo Nino/Nina can develop even without ENSO.