Ningaloo Nino/Nina and their regional climate impacts as recorded by corals along the coast of Western Australia

Ningaloo Nino/Nina is characterized by abnormal warming/cooling of sea surface temperature (SST) along the coast of Western Australia, leading to coastal marine ecosystem disruptions and abnormal climate conditions in the eastern Indian Ocean and Western Australia. Owing to short instrumental records, long-term Ningaloo Nino/Nina variability and its impacts on regional climate are less understood. In this study, coral delta O-18 records with bimonthly resolution from two sites along the Western Australian coast are used to investigate the relationship between coral delta O-18 and local SST. Significant correlations exist between coral delta O-18 and Ningaloo SST with 1-month lag, and thus the former is employed to represent Ningaloo Nino/Nina variability during 1854-1993. Coral delta O-18 reveals that the Ningaloo Nino/Nina features interdecadal variations, occurring more frequently in the periods of 1860-1890 and 1900-1970. Correspondingly, the impacts of Ningaloo Nino/Nina on the north-western Australian (NWA) rainfall exhibited marked interdecadal variations in the 20th century. Significant correlations between Ningaloo Nino/Nina and NWA rainfall occurred from 1900 to 1970, a period when frequent Ningaloo Nino/Nina events were recorded by coral delta O-18. An increase in the correlation with rainfall in the recent decades was revealed in the instrumental records. Therefore, our study indicates the potential of using tropical corals to study long-term Ningaloo Nino/Nina variability and their regional impacts.