Improving the Holocene glacier chronology of the Southern Alps/New Zealand enabling its reliable utilisation as palaeoclimatic archive
Final Report Abstract
New Zealand's Southern Alps offer excellent opportunities to investigate Holocene glacier chronologies in the southern hemispheric mid-latitudes. Limitations in representativeness and reliability of existing studies hamper, however, utilisation of their potential as palaeo-climatic archive. To substantially improve this situation was the main aim of the current research project. During field work, 54 samples for 10Be cosmogenic radionuclide dating were collected from boulder surfaces on moraines, 58,000 boulder surfaces were tested in situ for Schmidt-hammer exposureage dating, and detailed geomorphological mapping was conducted alongside geomorphologicalsedimentological analyses. Glacier forelands in central and eastern Aoraki/Mt.Cook National Park close to the Main Divide were studied, additionally localities in greater distance to the South-East in Arrowsmith, Ben Ohau, and Liebig Ranges. Seven rock glaciers in the Ben Ohau Range representing periglacial climatic indicators were included in the study and subsequent chronologic and palaeo-climatic interpretation. A strong glacial activity during the Early Holocene in the Arrowsmith Range, hitherto only based on results from Cameron Glacier, was confirmed by investigations at adjacent Ashburton Glacier and recognised as a regional signal. Rock glaciers in the Ben Ohau Range experienced strong morphodynamics immediately after their initiation in Early Holocene. Indicating repeated cold periods in Early Holocene followed by a reduced frequency during Mid- and Late Holocene, their palaeoclimatic evidence matches the established paradigm of a continuously decrease in dynamic of the primarily air temperature-driven glaciers from Early Holocene to the 'Little Ice Age'. By contrast, evidence for Early Holocene glacier advances is lacking in Aoraki/Mt.Cook National Park. A newly discovered, chronologically/geomorphologically convincingly verified Mid-Holocene moraine (5.640 ± 0.190 ka) at Classen Glacier remains (yet) as an individual case. Several glaciers reached their maximum Late Holocene expansion during the 'Little Ice Age' (18th century CE or later), whereas morainic evidence for older and more extensive Late Holocene glacier advances exists at some others. The overall number of the latter is, however, always lower than at wellknown Mueller Glacier. Consequently, it needs to be regarded as non-representative. A Holocene glacier chronology solely driven by air temperature is, in contrast to those ranges investigated located further east of the Main Divide, rather unlikely. Changes of intensity in the dominating westerly airflow and resulting precipitation patterns need additionally to be considered. Regionally specific geomorphological processes in the Southern Alps are causing a high degree of individuality connected to glacial landforms and their assemblages on glacier forelands. Differences of the basic glaciological and climatic conditions require a spatial differentiation with both Holocene glacier chronologies and palaeoclimatic history. To date's common practise of amalgamating results of glacial chronological studies without observing this individuality and spatial differentiation to achieve a 'representative' glacier chronology for Southern Alps as a whole seems no longer legitimate. Based on the results of the current research project, establishing glacier chronologies for clearly defined individual region with multiple glaciers being investigated constitutes an improved alternative approach. Additionally, the value of combining different dating techniques to minimise method-specific uncertainties is highlighted. Finally, detailed geomorphological mapping and analysis of those landforms interpreted in the context of studying glacier fluctuations should again be strengthened in the future.
Publications
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Potential for palaeoclimatic interpretation of periglacial landforms applying Schmidt-hammer exposure-age dating (SHD), examples from Norway and New Zealand. In: Brauer, A. & Schwab, M.J., eds. (2022): DEUQUA2022 Conference - Connecting Geoarchives Abstact Volume. GFZ Scientific Rechnical Reports STR 22/02, Potsdam: 147 - 148
Winkler, S.
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Potential of detailed geomorphological mapping for the study of Holocene glacier chronologies: Mueller Glacier, Southern Alps/New Zealand. EGU General Assembly 2022, Vienna, Austria, 23-27 Mai 2022
Winkler, S.
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Holocene glacier chronology of the Southern Alps/New Zealand - A reassessment based on Schmidt-hammer exposure-age dating (SHD) and geomorphological analysis. XXI.INQUA Congress, Rom, 13-20 Jul 2023, Abstract 489
Winkler, S.
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Improved chronological constraints for Holocene rock glacier activity in the Ben Ohau Range, Southern Alps/New Zealand. The Holocene, 35(3), 352-372.
Winkler, Stefan
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Improved chronological constraints on rock glacier activity in the Ben Ohau Range, Southern Alps/New Zealand. EGU General Assembly 2024, Wien, 14–19 Apr 2024, EGU24-2308
Winkler, S.
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Observations of paraglacial processes on glacier forelands and potential implications for regional denudation rates, Southern Alps/New Zealand. 4.IAG DENUCHANGE Workshop, Rom, 23–26 Sep 2024, Abstract 38
Winkler, S.
