A Bayesian Hierarchical Time Series Model for Reconstructing Hydroclimate from Multiple Proxies

TL;DR

This paper introduces a Bayesian hierarchical model that reconstructs past hydroclimate variability using multiple proxy records, providing probabilistic estimates and insights into historical climate extremes in Queensland, Australia.

Contribution

It presents a novel probabilistic reconstruction method combining time-series modeling with inverse prediction for hydroclimate proxies.

Findings

Reconstructed hydroclimate indices for Brisbane and Fitzroy catchments.

Estimated probabilities of past climate extremes beyond observed ranges.

Identified years with likely extreme hydroclimate behavior.

Abstract

We propose a Bayesian hierarchical model which produces probabilistic reconstructions of hydroclimatic variability in Queensland Australia. The model provides a standardised approach to hydroclimate reconstruction using multiple palaeoclimate proxy records derived from natural archives such as speleothems, ice cores and tree rings. The method combines time-series modelling with inverse prediction to quantify the relationships between a given hydroclimate index and relevant proxies over an instrumental period and subsequently reconstruct the hydroclimate back through time. We present case studies for Brisbane and Fitzroy catchments focusing on two hydroclimate indices, the Rainfall Index (RFI) and the Standardised Precipitation-Evapotranspiration Index (SPEI). The probabilistic nature of the reconstructions allows us to estimate the probability that a hydroclimate index in any reconstruction year was lower (higher) than the minimum (maximum) value observed over the instrumental period. In Brisbane, the RFI is unlikely (probabilities < 20%) to have exhibited extremes beyond the minimum/maximum values observed between 1889 and 2017. However, in Fitzroy there are several years during the reconstruction period where the RFI is likely (> 50% probability) to have exhibited behaviour beyond the minimum/maximum of what has been observed. For SPEI, the probability of observing such extremes since the end of the instrumental period in 1889 doesn't exceed 50% in any reconstruction year in Brisbane or Fitzroy.