The timing and cause of glacial advances in the southern mid-latitudes during the last glacial cycle based on a synthesis of exposure ages from Patagonia and New Zealand

• Published in: Quaternary Science Reviews
• Main Authors: Darvill, Christopher, Bentley, Michael, Stokes, Chris, Shulmeister, James
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2016
• Subjects: Last glacial cycle; Patagonia; New Zealand; Cosmogenic nuclide exposure dating; Glacial advances; Sea ice
• Online Access: https://research.manchester.ac.uk/en/publications/06dd09ea-6902-4e3b-95a0-9771afdf0688; https://doi.org/10.1016/j.quascirev.2016.07.024; http://dro.dur.ac.uk/19435/1/19435.pdf?DDD14+dgg4lp+d700tmt

Glacier advances in the southern mid-latitudes during the last glacial cycle (ca. 110–10 ka) were controlled by changes in temperature and precipitation linked to several important ocean-climate systems. As such, the timing of glacial advance and retreat can yield important insights into the mechanisms of Southern Hemisphere climate change. This is particularly important given that several recent studies have demonstrated significant glacial advances prior to the global Last Glacial Maximum (gLGM) in Patagonia and New Zealand, the cause of which are uncertain. The recent increase in chronological studies in these regions offers the opportunity to compare regional trends in glacial activity. Here, we compile the first consistent 10Be exposure-dating chronologies for Patagonia and New Zealand to highlight the broad pattern of mid-latitude glacial activity over the last glacial cycle. Our results show that advances or still stands culminated at 26–27 ka, 18–19 ka and 13–14 ka in both Patagonia and New Zealand and were broadly synchronous, but with an offset between regions of up to 900 years that cannot be explained by age calculation or physically plausible erosion differences. Furthermore, there is evidence in both regions for glacial advances culminating from at least 45 ka, during the latter half of Marine Isotope Stage (MIS) 3. Glacial activity prior to the gLGM differed from the large Northern Hemisphere ice sheets, likely due to favourable Southern Hemisphere conditions during late MIS 3: summer insolation reached a minimum, seasonality was reduced, winter duration was increasing, and sea ice had expanded significantly, inducing stratification of the ocean and triggering northward migration of oceanic fronts and the Southern Westerly Winds. Glacial advances in Patagonia and New Zealand during the gLGM were probably primed by underlying orbital parameters. However, the precise timing is likely to have been intrinsically linked to migration of the coupled ocean-atmosphere system, which may account for the ...