Although extended or ‘protracted’ El Niño and La Niña episodes were first suggested nearly 20 years ago, they have not received the attention of other ‘flavours’ of the El Niño–Southern Oscillation (ENSO) or low-frequency ‘ENSO-like’ phenomena. In this study, instrumental variables and palaeoclimatic reconstructions are used to investigate the most recent ‘protracted’ El Niño episode in 2014–2016, and place it into a longer historical context. Although just reaching the threshold for such an episode, the 2014–2016 ‘protracted’ El Niño had very severe societal, agricultural, environmental and ecological impacts, particularly in western Pacific regions like eastern Australia. We show that although ‘protracted’ ENSO episodes of either phase cause similar, near-global modulations of weather and climate as during more ‘classical’ events, impacts associated with ‘protracted’ episodes last longer, with strong influences in eastern Australia. The latter is a response to the dominance of Niño 4 sea surface temperature (SST) and associated atmospheric teleconnection anomalies during ‘protracted’ ENSO episodes. Importantly, while Niño 4 SST anomalies recorded during the austral summer of 2016 were the highest values on record, an analysis of long-term palaeoclimate records indicates that there may have been episodes of greater magnitude and duration than seen in instrumental observations. This suggestsmore »
Holocene El Niño–Southern Oscillation variability reflected in subtropical Australian precipitation
The La Niña and El Niño phases of the El Niño-Southern Oscillation (ENSO) have major impacts on regional rainfall patterns around the globe, with substantial environmental, societal and economic implications. Long-term perspectives on ENSO behaviour, under changing background conditions, are essential to anticipating how ENSO phases may respond under future climate scenarios. Here, we derive a 7700-year, quantitative precipitation record using carbon isotope ratios from a single species of leaf preserved in lake sediments from subtropical eastern Australia. We find a generally wet (more La Niña-like) mid-Holocene that shifted towards drier and more variable climates after 3200 cal. yr BP, primarily driven by increasing frequency and strength of the El Niño phase. Climate model simulations implicate a progressive orbitally-driven weakening of the Pacific Walker Circulation as contributing to this change. At centennial scales, high rainfall characterised the Little Ice Age (~1450–1850 CE) in subtropical eastern Australia, contrasting with oceanic proxies that suggest El Niño-like conditions prevail during this period. Our data provide a new western Pacific perspective on Holocene ENSO variability and highlight the need to address ENSO reconstruction with a geographically diverse network of sites to characterise how both ENSO, and its impacts, vary in a changing climate.
- Publication Date:
- NSF-PAR ID:
- 10153377
- Journal Name:
- Scientific Reports
- Volume:
- 9
- Issue:
- 1
- ISSN:
- 2045-2322
- Publisher:
- Nature Publishing Group
- Sponsoring Org:
- National Science Foundation
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