A 2000 year record of hydroclimate variability inferred from oxygen isotopes in lake sediments on Kangaroo Island, South Australia

High resolution records of past hydroclimate are crucial for understanding the recurrence of extreme climatic events (prolonged droughts and deluges) and for robust decision making around environmental and economic sustainability. The current study presents a ~sub-decadal-scale hydroclimate reconstruction based on oxygen isotope analysis of lake sediment ostracod shells, extracted from the sediments of Lashmars Lagoon, Kangaroo Island, South Australia. Spanning the last ~2000 years, the oxygen isotope record records a series of multi-decadal wet and dry periods, manifest in the relative precipitation-evaporation balance of the lake. Of note, the record implies periods of prolonged declines in water balance, tentatively interpreted as droughts, during the periods 525-575 CE, 770-790 CE, 825-850 CE, and 980-1020 CE. By contrast, the periods from ~150-450 CE and 600-750 CE were relatively wet. Unfortunately, ostracods were absent within the sediments deposited between 1250-1590 CE, possibly due to a reduction in lake water or sediment pH following a notable increase in charcoal deposition. The period from ~1590-1800 CE appears to have been notably dry, prior to an increase in effective moisture during the last 200 years. The Lashmars Lagoon record exhibits similar trends to a record from Blue Lake, Mt. Gambier, approx. 500 km to the southeast. However, these records contrast with other hydroclimate records from further east, implying a complex relationship with regional climate drivers. Comparison with instrumental period rainfall data, and reconstructed indices for major ocean–atmosphere interactions suggests that periods of increased moisture balance on Kangaroo Island were influenced by a combination of Southern Ocean and Indian Ocean derived climate influences.