Southern westerly wind migrations and contributions to Holocene and previous interglacial climates
Creators: name: Riechelson, Hailey Michelle
Publisher: name: No Publisher Supplied
Year: 2023

description: The Chilean Margin region influences, and is influenced by, ocean-atmosphere, land-ocean, and surface-subsurface interactions. This area is home to the South Westerly Winds (SWW), whose strength and positions have broad implications for Southern Hemisphere and global climate through changes to precipitation, carbon dioxide, and heat storage. Existing regional records are limited by either time scale or resolution, which in turn limits our picture of a complex system. By creating a series of high-resolution Holocene records, we can assess SWW variability in response to various forcings and their relationship to global CO2. In this thesis I apply a multiproxy approach, including X-ray Fluorescence (XRF), stable isotope, and total organic carbon analyses among others, to reconstruct high resolution records of SWW migrations and Chilean Margin conditions during the Holocene and Pleistocene interglacial periods. High resolution, temporally extensive Chilean Margin records, can help us better understand how observed changes fit into the context of the South Pacific, the broader Holocene, and Pleistocene interglacial periods. The first chapter of my thesis focuses on solar forced centennial scale SWW variability. XRF analysis will be used to produce a ~2-year resolution aluminum record, a product of continental weathering in response to precipitation, representing SWW migration. It then ties resulting SWW migrations to Antarctic temperature variability using benthic δ13C data. Chapter 2 relies on productivity and nutrient consumption proxies to assess downstream effects of Southern Ocean biological pump inefficiency and, in doing so, helps solidify the leaky biological pump’s role in global atmospheric CO2 concentrations. Total organic carbon, Bromine XRF data, and bulk sediment nitrogen isotopes are included to obtain a full picture of nutrient availability and primary productivity along the Chilean Margin. Comparison with high and low latitude isotopic and primary productivity records constrains the fate of nutrients as they are transported through the Southeast Pacific.The third chapter revisits the question as to whether Holocene CO2 increase is truly anomalous among interglacial periods. We reconstruct SWW movement from 6 interglacial periods utilizing aluminum XRF data and compare these with records of CO2, Antarctic temperature, and Antarctic summer duration. We find that the SWWs track changes in Antarctic summer duration during all interglacials examined except the Holocene, which suggests the winds, and thus CO2, responded to a different, anomalous forcing during the Holocene. This result further suggests the SWW are more sensitive to perturbations than previously expected.Collectively, I explore a few running themes throughout these chapters including the role of the SWW in global climate, connection between high-, mid-, and low-latitudes, and climate system amplification of small initial perturbations. The results demonstrate the sensitivity of the SWW system to small radiative perturbations and the connectedness between the tropics and poles via the mid-latitudes.