Oxygen isotopes from Patagonian lakes as paleoclimate proxies

LUCKE, A.; LAPRIDA C.; ZOLICSTKA, B; MAYR, C.; MASSAFERRO, J.; . OHLENDORF, C.; WISSEL, H.; MEIER, W

Berlin

Workshop; Climate Impacts on Glaciers and Biosphere in Fuego-Patagonia".; 2017

Humboldt-Universität zu Berlin Geographisches Institut Klimageographie

The belt of the Southern Hemisphere Westerlies (SHW) is considered to have played an important role for global climate change. However, testing such a hypothesis is hampered by inconsistencies between both models and proxy records regarding intensity and latitudinal shifts of the SH W belt in the late Quaternary. Oxygen isotope proxies from lake sediments can be used to tackle questions related to past atmospheric dynamics and associated hydrological changes in Patagonia, presently located in the SHW core region. The modern database needed for the calibration of isotope proxies from this remote region, however, is extremely poor. To overcome this lack of data, samples of surface water and precipitation from Chilean and Argentinean Patagonia were nvestigated. The isotope ratios of precipitation strongly reflect patiotemporal patterns caused by orographic, latitudinal, and continental effects. Thewater balance has a strong influence on the isotopic composition of lake water. Bathymetry, exposition to wind, inflows, outflows, and climatic settings influence the water balances of Patagonian lakes. As a consequence, the choice of adequate sites and of reliable recorders of the oxygen isotopic composition of the lake water is important. Methodologically refined isotope proxies, such as oxygen isotope ratios of aquatic cellulose, provided promising results in calibration studies. Combined oxygen isotope records from aquatic mosses and authigenic carbonates, continuously covering the last 26,000 years at the ICDP site Laguna Potrok Aike in the Patagonian steppe, indicated an early gradual warming starting around 18,000 years ago and extreme drought conditions in the early to mid-Holocene in the Patagonian steppe region. Future investigations aim at densifying the isotopic network and comparing isotope records from multiple proxies and archives.