Trends in Tropical Variability Since the 18th Century: A New View from Northern Australian Corals
Abstract
Interannual climate variability across the tropical Indo-Pacific is largely orchestrated by the El Niño-Southern Oscillation (ENSO) system, and changes in the strength of this variability have important implications for past, present, and future climate. The short and sparse nature of instrumental data in the core ENSO region has motivated dozens of studies that use the geochemistry of coral skeletons to reconstruct past ENSO-related changes in temperature and rainfall. Additional investigations have combined these records to produce geographically broad reconstructions of the state of the ENSO system that extend over several centuries. A common feature of such multi-site analyses is a substantial increase in apparent ENSO variance since the 19th century. However, such a trend can result from systematic or random biases. For example, coral age model uncertainty flattens variance when imperfectly dated records are combined, and data density in the core ENSO region increases over time. Here we present three new oxygen isotope records from northern Australia corals whose interannual variance is correlated with ENSO. These corals originate from Nightcliffe Reef (Darwin), Jeannie River (northern Great Barrier Reef), and Bramble Cay (Gulf of Papua). We show that none of these ENSO-sensitive records indicates a trend towards increased interannual variance over the past 200+ years (up to their collection dates in the 1980s). We further compare this regional perspective with variance changes in other single-core ENSO reconstructions to evaluate a) whether consistent variance trends can be identified in the pre-instrumental era, and b) how particular biases impact the reconstruction of ENSO variance from coral records.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMPP034..03C
- Keywords:
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- 3305 Climate change and variability;
- ATMOSPHERIC PROCESSES;
- 3337 Global climate models;
- ATMOSPHERIC PROCESSES;
- 3344 Paleoclimatology;
- ATMOSPHERIC PROCESSES