Abstract
Abstract. The dominant modes of climate variability on interannual timescales in the tropical Indian Ocean are the El Niño–Southern Oscillation (ENSO) and the Indian Ocean Dipole. El Niño events have occurred more frequently during recent decades, and it has been suggested that an asymmetric ENSO teleconnection (warming during El Niño events is stronger than cooling during La Niña events) caused the pronounced warming of the western Indian Ocean. In this study, we test this hypothesis using coral Sr∕Ca records from the central Indian Ocean (Chagos Archipelago) to reconstruct past sea surface temperatures (SSTs) in time windows from the mid-Little Ice Age (1675–1716) to the present. Three sub-fossil massive Porites corals were dated to the 17–18th century (one coral) and the 19–20th century (two corals). Their records were compared with a published modern coral Sr∕Ca record from the same site. All corals were subsampled at a monthly resolution for Sr∕Ca measurements, which were measured using a simultaneous inductively coupled plasma optical emission spectrometer (ICP-OES). Wavelet coherence analysis shows that interannual variability in the four coral records is driven by ENSO, suggesting that the ENSO–SST teleconnection in the central Indian Ocean has been stationary since the 17th century. To determine the symmetry of El Niño and La Niña events, we compiled composite records of positive and negative ENSO-driven SST anomaly events. We find similar magnitudes of warm and cold anomalies, indicating a symmetric ENSO response in the tropical Indian Ocean. This suggests that ENSO is not the main driver of central Indian Ocean warming.
Highlights
As the impacts of global climate change increase, paleoclimate research is more important than ever
The concept of “asymmetric” and “symmetric” El Niño–Southern Oscillation (ENSO) teleconnection refers to the magnitudes of warming and cooling during El Niño and La Niña events., i.e., we examine whether Indian Ocean warming during El Niño events is stronger than cooling during La Niña events
Trace amounts of diagenetic phases were detected in the sub-fossil coral samples, which show a good to excellent preservation according to the criteria defined in Cobb et al (2013)
Summary
As the impacts of global climate change increase, paleoclimate research is more important than ever. The Indian Ocean is of major relevance to global ocean warming as it has been warming faster than any other ocean basin during the last century and is the largest contributor to the current rise of global mean sea surface temperatures (SSTs; Roxy et al, 2014). Depending on the SST dataset, warming in the Indian Ocean is highest in the Arabian Sea (Roxy et al, 2014) or in the central Indian Ocean (Roxy et al, 2020). M. Leupold et al.: ENSO and internal sea surface temperature variability
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
