Late Quaternary glacier-climate reconstructions from the Southern Alps, New Zealand

• Main Author: Levan Tielidze (8514879)
• Format: Thesis
• Language: unknown
• Published: 2022
• Subjects: Glaciology; Palaeoclimatology; Quaternary Environments; Surface Processes; Last Glacial Maximum; Last Glacial Termination; Late Glacial; Antarctic Cold Reversal; Equilibrium-line altitude; Snowline; Past Climate; Cosmogenic surface exposure dating; Palaeo Lake; New Zealand; School: School of Geography; Environment and Earth Sciences; Unit: Antarctic Research Centre; 040602 Glaciology; 040605 Palaeoclimatology; 040606 Quaternary Environments; 040607 Surface Processes; Degree Discipline: Physical Geography; Degree Discipline: Earth Sciences; Degree Discipline: Geology; Degree Discipline: Environmental Studies; Degree Discipline: New Zealand Studies; Degree Level: Doctoral; Degree Name: Doctor of Philosophy; Antarctic; Ela; Moraine Ridge; Antarc*
• Online Access: https://doi.org/10.26686/wgtn.21708491

One of the outstanding problems in modern geoscience is identifying the cause of past climate changes, particularly the drivers of rapid climate change during Quaternary glacial cycles. Changes in the physical geography of Earth’s surface during the Late Quaternary are mainly dependent on glacial dynamics – periods of rapid warming produced significant amounts of meltwater that reshaped the landscape, changed global sea-level and influenced climate. Identifying the timing of key climate transitions during past warming episodes, such as the last glacial termination, may help to understand the future evolution of Earth’s climate system (e.g. Denton et al., 2021). In this thesis, using geomorphological mapping and sixty-six cosmogenic 10Be surface exposure ages obtained from ice sculpted bedrock surfaces and deposited moraine landforms, I constrain the local Last Glacial Maximum and subsequent timing of last glacial termination in the Ahuriri River valley, Southern Alps, New Zealand (44°15′S, 169°36′E). Using the maximum elevation of lateral moraine (MELM) and accumulation area ratio (AAR) methods, along with application of a temperature lapse rate, I estimate the equilibrium-line altitude (ELA) and associated temperatures from the same periods. The largest glacial event in the Ahuriri River valley occurred at 19.8±0.3 ka when the former Ahuriri Glacier reached its maximum extent, which coincides with the global Last Glacial Maximum. By 16.7±0.3 ka, ice had retreated ~18 km up-valley from the LGM position and deglaciation was accompanied by the formation of a shallow proglacial lake. Surface exposure ages from moraines situated in a tributary of the upper Ahuriri River valley indicate that a subsequent advance of the palaeo glacier culminated at 14.5±0.3 ka, while the next readvance or still stand occurred at 13.6±0.3 ka. About 1000 yr later (12.6±0.2 ka), the former glacier built another prominent terminal moraine ridge in the lower section of the upper right tributary valley. Reconstructions of past glacier ...