Modern to Late Pleistocene Stable Isotope Climatology of Alaska

• Main Author: Sloat, Alison
• Format: Text
• Language: English
• Published: Digital Scholarship@UNLV 2014
• Subjects: Alaska; Climatic changes; Deuterium; Oxygen—Isotopes; Paleoclimatology; Stable isotopes; Climate; Geochemistry; Geology; Gulf of Alaska; Yukon; Ice; permafrost; wedge*
• Online Access: https://digitalscholarship.unlv.edu/thesesdissertations/2143; https://digitalscholarship.unlv.edu/cgi/viewcontent.cgi?article=3144&context=thesesdissertations

Understanding modern controls on climate is necessary to interpret past climatic conditions. This project investigated the modern controls on δ18O and δD values in Alaskan surface waters to interpret the controls on Late Pleistocene climate variability. ArcGIS was used to develop an isoscape of modern δ18O and δD values of over 400 surface water samples collected across Alaska and the Yukon. It was found that winter temperature and precipitation have the greatest controls on δ18O and δD values in Alaska, resulting in high δ18O values along the coast of the Gulf of Alaska and low values inland toward Central Alaska. This isoscape can be applied to paleoenvironmental, modern, and future records to determine isotope-precipitation-temperature values. This is a useful tool in determining paleotemperatures of Alaska which is necessary for the interpretation of the magnitude, timing, and patterns of past response to climatic change. Previous work suggested ancient preserved ice wedges in the CRREL Permafrost Tunnel formed syngenetically during Marine Isotope Stage 3 (MIS 3). However, a new method of determining the timing of ice wedge and pool ice formation using radiocarbon-dated DOC and CO2 reveals that the features are much younger than previously thought and are epigenetic in origin. At least five freeze events and one melt event are apparent in the tunnel, with likely ages between 26 and 12.9 cal ka BP, during MIS 2. The prevalence of inversions in the radiocarbon ages indicates that carbon may persist for as long as 17,000 years within permafrost environments, potentially providing anomalous age dates when dating carbon in permafrost. To better constrain the timing and climatic conditions during ice wedge formation, eight ice wedges and seven ice pools were sampled at high temporal resolution for stable isotopes and were combined with14C ages of DOC from within the ice to estimate the timing of formation and climatic conditions under which they formed. Four intervals of cooling and one interval of warming were ...