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Regional patterns of hydroclimate variability in southeastern Australia over the past 1200 years
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  • Bronwyn C Dixon,
  • Jonathan T Tyler,
  • Benjamin James Henley,
  • Russell Drysdale
Bronwyn C Dixon
University of Melbourne

Corresponding Author:[email protected]

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Jonathan T Tyler
University of Adelaide
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Benjamin James Henley
University of Melbourne
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Russell Drysdale
University of Melbourne
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Abstract

Long, continuous palaeoclimate records provide an opportunity to extend knowledge of decadal to multi-decadal scale climate variability beyond the limit of instrumental records. In this study, quality-controlled proxy records from southeastern Australia are examined for coherent variability during the Common Era, with age uncertainty for each record estimated using iterative age modeling. Site-level empirical orthogonal functions (EOFs) are derived from multivariate records for the purpose of objective comparison of climate signals between sites without selection bias. A regional Monte Carlo EOF (MCEOF) analysis is conducted on combined time-uncertain single-proxy records and site-level EOFs. The analysis identifies two robust vectors, which are inferred to represent hydroclimate changes. The first regional MCEOF suggests an increase in effective moisture between 900 – 1750 CE. Agreement between regional MCEOF1 and Australian temperature reconstructions suggests suppressed evaporation was a significant influence on regional effective moisture during this time. Regional MCEOF2 exhibits shorter, centennial-scale oscillations that show some similarity with rainfall reconstructions based on remote high-resolution proxies. We interpret MCEOF2 to represent regional-scale rainfall patterns driven by changes in seasonal rainfall and the influence of the Southern Annular Mode over southern Australian rainfall. This study presents the first quantitative regional synthesis of southeastern Australian hydroclimate reconstructions from multivariate sedimentary archives covering the last 1200 years. The resulting MCEOFs demonstrate the utility of low-resolution climate records from this region, but also highlight the limitations of the existing data network, which must be resolved through the generation of new records.