Climate reconstructions for the Last Glacial Maximum from a simple cirque glacier in Fiordland, New Zealand. (1st January 2022)

• Record Type: Journal Article
• Authors: Moore, Emily M.M.; Eaves, Shaun R.; Norton, Kevin P.; Mackintosh, Andrew N.; Anderson, Brian M.; Dowling, Lisa H.; Hidy, Alan J.
• Is Part Of: Quaternary science reviews. Volume 275(2022)
• Publication Date: 2022-01-01
• Subjects: Quaternary -- Pleistocene -- Glaciation -- Paleoclimatology -- Southern pacific -- Cosmogenic isotopes -- Geomorphology -- Glacial -- Equilibrium line altitude -- Degree day modelling; Geology, Stratigraphic -- Quaternary -- Periodicals; Stratigraphie -- Quaternaire -- Périodiques; 551.79
• DOI: 10.1016/j.quascirev.2021.107281
• Languages: English
• ISSNs: 0277-3791

Abstract

Abstract: Mountain glacier records offer important constraints on the timing and magnitude of climate variability during the last glacial cycle. Existing moraine chronologies from the central Southern Alps indicate maximum ice extent was achieved during marine isotope stages 3–4, followed by repeated advances of similar, but gradually declining extent during marine isotope stage 2, until onset of the glacial termination. Questions remain over the precise role of climate in driving these changes, as most existing moraine chronologies come from large, complex former valley glacier systems, where non-climatic influences such as changing bed topography and proglacial lake formation may have influenced glacier length changes. Here we address this problem via a new cosmogenic 10 Be chronology and equilibrium line altitude reconstruction from a cirque glacier situated in Fiordland, New Zealand. Our chronology shows moraine deposition at 32 ± 11 ka, 18.7 ± 0.2 ka, 18.1 ± 0.1 ka, and c. 17.2 ± 0.3 ka. The simple geometry of the former glacier supports the role of climate in driving a net decline of regional ice volume during marine isotope stages 3–2. Close spacing and good preservation of the 19–17 ka moraines permits 2D glacier reconstruction which suggests the equilibrium line altitude remained depressed by c.1130 m (equivalent to 5.8 ± 0.6 °C colder than present) during this interval. Onset of warming after 17.2 ± 0.2 ka is consistent with climate proxy evidence for a sustained southward shift in the southern westerly winds, which may have promoted deglaciation via shifting ocean currents and promoting increases in atmospheric carbon dioxide. Highlights: Moraine ages from southern New Zealand constrain ice extent during last glacial. Equilibrium line altitude was 1100 m lower than present at the Last Glacial Maximum. Regional air temperatures remained depressed by c. 6 °C until 17 ka.