Exploring Pacific Island hydroclimatic extremes using the South Pacific Drought Atlas
- 1Water Research Centre, School of Civil and Environmental Engineering, University of New South Wales, Australia
- 2ARC Centre of Excellence in Australian Biodiversity and Heritage, University of New South Wales, Australia
- 3Chronos 14Carbon-Cycle Facility, Mark Wainwright Analytical Centre, University of New South Wales, Australia
- 4Water Research Laboratory, School of Civil and Environmental Engineering, University of New South Wales, Australia
- 5University of Technology Sydney, Sydney, Australia
Droughts are a natural occurrence in many small Pacific Islands and can have severe impacts on local populations and environments. The El Niño-Southern Oscillation (ENSO) is a well-known driver of drought in the South Pacific, but our understanding of extreme ENSO events and their influence on island hydroclimate is limited by the short instrumental record and the infrequency of ENSO extremes. To address this gap, we present the South Pacific Drought Atlas (SPaDA), a multi-proxy, spatially resolved reconstruction of the November-April Standardised Precipitation Evapotranspiration Index for the southwest Pacific islands. The reconstruction integrates coral proxies, which provide local information on the South Pacific hydroclimate but are limited in number and length, with a network of continental tree-ring chronologies targeting Pacific climate variability through remote teleconnections. The reconstruction demonstrates the benefits of multi-proxy reconstructions incorporating tree rings, which allow for the alignment of other proxy records without chronological error.
The SPaDA provides a 350-year, continuous dataset of climate information, which can be used to explore the occurrence of extreme events in the pre-instrumental period. The SPaDA closes the gap between existing paleo-reconstructions of point ENSO indices, and a spatially resolved drought atlas, allowing both the hydroclimate of individual islands and regional patterns of drought to be assessed. The benefit of a spatially resolved dataset to assess climate extremes in small Pacific islands is highlighted in the case of extreme El Niño events, which can have substantially different hydroclimatic impacts than more moderate events.
We used an Isolation Forest, an unsupervised machine learning algorithm, to identify anomalous hydroclimatic states in the SPaDA that may indicate the occurrence of an extreme event. Extreme El Niño events characterised by very strong southwest Pacific drought anomalies and a zonal South Pacific Convergence Zone orientation are shown to have occurred semi-regularly throughout the reconstruction interval, providing a valuable baseline to compare to climate model projections. By identifying the spatial patterns of drought resulting from extreme events, we can better understand the impacts these events may have on individual Pacific Islands in the future.
How to cite: Higgins, P., Palmer, J., Johnson, F., Andersen, M., and Turney, C.: Exploring Pacific Island hydroclimatic extremes using the South Pacific Drought Atlas, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-10570, https://doi.org/10.5194/egusphere-egu23-10570, 2023.
