New insights into southern mid-latitude climate change from the terrestrial Roaring Forties

• Main Author: MacGregor, Claire Louise Verden
• Format: Doctoral or Postdoctoral Thesis
• Language: unknown
• Published: 2023
• Subjects: Palaeoclimatology; Isotope geochemistry; Quaternary environments; Antarctic; Greenland; Southern Ocean; The Antarctic; Antarc*; Antarctica
• Online Access: http://hdl.handle.net/11343/333746

© 2023 Claire Louise Verden MacGregor Most of our understanding of Quaternary climate change stems from records derived from the polar regions and the Northern Hemisphere. The forcing mechanisms and terrestrial response to Quaternary climate change in the Southern Hemisphere remain ambiguous owing to a paucity of precisely dated palaeoclimate data. This limits our ability to assess the Southern Hemisphere’s response to large-scale changes in climate beyond the Antarctic region and south of the tropics. The Southern Hemisphere holds significant potential for understanding global climate as a coupled ocean-atmosphere system due to the presence of the mid-latitude south westerly trade winds (SWW) and the Southern Ocean. These key features are fundamental in the transfer of climate signals through global atmospheric and oceanic teleconnections. Tasmania, Australia, is situated between 40-44 degrees south and is unique in that it is one of just three southern mid-latitude landmasses that directly intercept the SWW. It provides the opportunity to track the meridional shifts and climatic significance of the position of the SWW. This thesis explores fundamental aspects of Tasmania's hydroclimate variability over different timescales to understand the driving mechanisms and the regional climatic response. It presents new, precisely dated speleothem records that contribute towards building an integrated understanding of climate forcing mechanisms in a global context. This is crucial in resolving broader palaeoclimate enigmas such as the influence of Antarctica on terrestrial systems to the north and defining the boundary between the Antarctic and Greenland-like responses to millennial-scale events. The new Tasmanian speleothem data reveals a strong coupling with hydroclimate, contributing valuable insights into the meridional movement in the SWW. The speleothem d13C displays a strong, orbitally paced mode of rainfall variability throughout the Last Glacial Period that closely tracks changes in summer insolation at 65N ...