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

Abstract

Ningaloo Niño/Niña 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 Niño/Niña variability and its impacts on regional climate are less understood. In this study, coral δ18O records with bimonthly resolution from two sites along the Western Australian coast are used to investigate the relationship between coral δ18O and local SST. Significant correlations exist between coral δ18O and Ningaloo SST with 1-month lag, and thus the former is employed to represent Ningaloo Niño/Niña variability during 1854–1993. Coral δ18O reveals that the Ningaloo Niño/Niña features interdecadal variations, occurring more frequently in the periods of 1860–1890 and 1900–1970. Correspondingly, the impacts of Ningaloo Niño/Niña on the northwestern Australian (NWA) rainfall exhibited marked interdecadal variations in the 20th century. Significant correlations between Ningaloo Niño/Niña and NWA rainfall occurred from 1900 to 1970, a period when frequent Ningaloo Niño/Niña events were recorded by coral δ18O. 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 Niño/Niña variability and their regional impacts.