Summary
The mid- to high-latitudes of the Southern Hemisphere are dominated by the westerly winds. These are important because changes in their strength determine precipitation and temperature regimes. However, little is known about their past strength, or spatial and temporal variability. Sub-Antarctic islands are the only landmasses between Antarctica, South America, Africa and Australia where terrestrial climate and ecosystem records are available, making them crucial locations for linking southern mid- and high-latitude regions. However, few long-term climate and ecosystem records exist. This project aims to address these gaps by utilising lake sediment cores from Macquarie Island (54°30’S, 159°57’E) to reconstruct changes in wind strength and identify ecosystem shifts over time. A marked west-east gradient in salinity exists across the island as saline ions are delivered by wind-derived sea spray. A diatom-salinity model was established and applied to a sediment core dated using 210Pb and 14C. This was used to infer past lake water salinity and wind strength (i.e. higher salinity implies stronger winds). Windier conditions prevailed during the early-mid Holocene (7000-5500 years BP), followed by a period of reduced wind strength. After c. 4700 years BP conditions became windier. An abrupt change in sedimentation rate occurred c. 4000 years BP, following a peak in wind strength. A period of slow sedimentation occurred from 4000 years BP, possibly due to drier conditions. Comparisons to other studies in the sub-Antarctic region and mid- and high-latitudes of the Southern Hemisphere were made to investigate broader-scale changes in wind strength and ecological responses to changing climatic conditions.