Understanding Climate History and Ice Extent in the Mid- to High Latitudes of the Southern Hemisphere During the Last Glacial Maximum

• Main Author: King, Courtney
• Format: Text
• Language: unknown
• Published: DigitalCommons@UMaine 2017
• Subjects: Last glacial maximum; Antarctica; radiocarbon; New Zealand; beryllium-10; Climate; Other Earth Sciences; Hatherton Glacier; Pukaki; Transantarctic Mountains; Wellman; Antarc*
• Online Access: https://digitalcommons.library.umaine.edu/etd/2736; https://digitalcommons.library.umaine.edu/context/etd/article/3803/viewcontent/D_KingCourtney_Final.pdf

Understanding causes of past climate fluctuations provides insight into the potential drivers of Earth’s ice-age cycles as well as present-day changes. In this work, I constructed chronologies of past ice behavior in the mid- and high latitudes of the Southern Hemisphere, covering the period at and since the Last Glacial Maximum. In the Southern Hemisphere mid-latitudes, I mapped the surficial glacial geomorphology of the right-lateral moraines in the Pukaki Basin. In addition, I collected rock samples from boulders well stuck-into moraine ridges and carried out the quartz and beryllium chemistry for the 10Be surface exposure age dating method. To carry out research in the high latitudes, I worked in ice-free regions of the Transantarctic Mountains mapping surficial glacial geomorphology and collecting ancient algae samples in close association with past ice-dammed ponds. The radiocarbon-dated algae samples afford insight into the ice-thinning history in the region. Moraines in two sectors of the right-laterals and one sector of the terminals in Pukaki Basin represent pulses of the former Pukaki glacier during the end of the last glacial period. The surface exposure age chronologies from all three sectors date moraine belts to 18,400 ± 270 yrs, 18,870 ± 110 yrs, 19,390 ± 270 yrs, 20,120 ± 760 yrs and 20,450 ± 560 yrs. The 10Be ages from this work document an expansive glacier at ~19,000 yrs ago, a period not yet captured in this system, despite previous work on the left-lateral moraine belts. The radiocarbon chronology from the Lake Wellman region, alongside lower Hatherton Glacier, indicates that the timing of the Last Glacial Maximum was achieved ~9500 yr BP. Recessional chronologies from regions adjacent to both lower and upper Hatherton Glacier, indicate fairly steady retreat from ~9000-4000 yr BP. By mid- to late Holocene, Hatherton Glacier had thinned to within ~50 m of its present-day elevation. In addition to maximum and thinning histories, there are limited radiocarbon ages from both regions that ...