The New Zealand subantarctic islands of Auckland and Campbell, situated between the subtropical front and the Antarctic Convergence in the Pacific sector of the Southern Ocean, provide valuable terrestrial records from a globally important climatic region. Whilst the islands show clear evidence of past glaciation, the timing and mechanisms behind Pleistocene environmental and climate changes remain uncertain. Here we present a multidisciplinary study of the islands-including marine and terrestrial geomorphological surveys, extensive analyses of sedimentary sequences, a comprehensive dating programme, and glacier flow line modelling-to investigate multiple phases of glaciation across the islands. We find evidence that the Auckland Islands hosted a small ice cap 384 000 +/- 26 000 years ago (384 +/- 26 ka), most likely during Marine Isotope Stage 10, a period when the subtropical front was reportedly north of its present-day latitude by several degrees, and consistent with hemispheric-wide glacial expansion. Flow line modelling constrained by field evidence suggests a more restricted glacial period prior to the LGM that formed substantial valley glaciers on the Campbell and Auckland Islands around 72-62 ka. Despite previous interpretations that suggest the maximum glacial extent occurred in the form of valley glaciation at the Last Glacial Maximum (LGM; similar to 21 ka), our combined approach suggests minimal LGM glaciation across the New Zealand subantarctic islands and that no glaciers were present during the Antarctic Cold Reversal (ACR; similar to 15-13 ka). Instead, modelling implies that despite a regional mean annual air temperature depression of similar to 5 degrees C during the LGM, a combination of high seasonality and low precipitation left the islands incapable of sustaining significant glaciation. We suggest that northwards expansion of winter sea ice during the LGM and subsequent ACR led to precipitation starvation across the middle to high latitudes of the Southern Ocean, resulting in restricted glaciation of the subantarctic islands.
1.Univ Keele, Sch Geog Geol & Environm, ICELAB, Keele ST5 5BG, Staffs, England 2.Univ New South Wales, Sch Biol Earth & Environm Sci, Palaeontol Geobiol & Earth Arch Res Ctr PANGEA, Sydney, NSW, Australia 3.Univ New South Wales, Australian Res Council, Ctr Excellence Australian Biodivers & Heritage CA, Sydney, NSW 2052, Australia 4.Victoria Univ Wellington, Antarctic Res Ctr, Wellington 6140, New Zealand 5.GNS Sci, Lower Hutt 5011, New Zealand 6.Landcare Res, Long Term Ecol Lab, Lincoln, New Zealand 7.Univ Auckland, Sch Environm, Private Bag 92019, Auckland 1142, New Zealand 8.Univ Waikato, Waikato Radiocarbon Lab, Private Bag 3105, Hamilton, New Zealand 9.Univ Waikato, ARC, Ctr Excellence Australian Biodivers & Heritage, Hamilton 3240, New Zealand 10.Univ Wollongong, Sch Earth & Environm Sci, Ctr Archaeol Sci, Wollongong, NSW, Australia 11.Univ Wollongong, ARC, Ctr Excellence Australian Biodivers & Heritage, Wollongong, NSW 2522, Australia 12.Univ Exeter, Dept Geog, Exeter EX4 4RJ, Devon, England 13.Univ Dundee, Sch Environm, Nethergate DD1 4HN, Scotland 14.Univ Colorado, Inst Arctic & Alpine Res, Boulder, CO 80309 USA 15.Stockholm Univ, Bolin Ctr Climate Res, Stockholm, Sweden 16.Stockholm Univ, Dept Geol Sci, Stockholm, Sweden 17.Univ New South Wales, ARC, Ctr Excellence Climate Syst Sci, Sydney, NSW, Australia 18.Gondwana Tree Ring Lab, POB 14, Canterbury 7546, New Zealand 19.Victoria Univ Wellington, Sch Geog Environm & Earth Sci, Wellington, New Zealand 20.Univ East Anglia, Sch Environm Sci, Ctr Ocean & Atmospher Studies, Norwich NR4 7TJ, Norfolk, England
Recommended Citation:
Rainsley, Eleanor,Turney, Chris S. M.,Golledge, Nicholas R.,et al. Pleistocene glacial history of the New Zealand subantarctic islands[J]. CLIMATE OF THE PAST,2019-01-01,15(2):423-448