A review of New Zealand palaeoclimate from the Last Interglacial to the global Last Glacial Maximum

• The paper reviews information from all main proxy sources on the palaeoclimate of New Zealand over the Last Glacial Cycle from about 130 ka until 20 ka BP.
• Evidence shows that the “bi-polar see-saw” recognised from climatic events in polar regions is not so evident in mid-latitude New Zealand possibly because the thermal see-saw effect diminishes with distance from the poles.
• The largest glacial advance of the Last Glacial Cycle in New Zealand was centred on 67–62 ka BP rather than during the global LGM, which yielded the second largest advance.
• The onset of the global LGM in New Zealand occurred abruptly after 33.433 ± 0.130 ka, and by 32–31 ka valley glacier ice depth had reached a maximum.At least 12 000 years before global ice volume reached its LGM maximum (19–18 ka).
• Ten major climatic events are recognised between 130 ka and 20 ka BP inclusive, comprising 5 warm intervals and 5 cool intervals, and including 6 valley glacier advances in addition to the global LGM.

Results from terrestrial and marine palaeoclimate proxies are integrated to reconstruct palaeoclimate variations in New Zealand from the Last Interglacial to the global Last Glacial Maximum (gLGM). By combining data from 21 speleothems we have constructed composite O–C stable isotope sequences from 0 to 88.5 ka BP and from 107.8 to 128.2 ka BP. The gaps in the sequence (a 19.3 ka break in coverage in MIS 5b/c and a 2.97 ka gap in MIS 5a) preclude the construct of a continuous record; so data were referenced to a common scale by normalising individual records (subtracting means and dividing by standard deviation). Overlapping records were then merged chronologically. These records were compared to integrated summer insolation for 45°S and to terrestrial and marine environmental proxies available for the New Zealand region.The MIS 5e thermal maximum in New Zealand was around 128–122 kiloyears BP (ka BP) and therefore similar in timing to the Last Interglacial in Australia, southern Europe and Greenland. Temperatures in parts of the North Island may have been 2°–3 °C warmer than present and the sea rose 3–6 m above modern level. In MIS 5d and 5b cool conditions with glacial advances occurred in the South Island, but from about 87 to 73 ka in MIS 5a warmth within 2 °C of present characterised most of the interstadial (locally termed the Otamangakau Interstadial).Conditions then cooled rapidly and culminated in a MIS 4 glacial advance that was the greatest of the New Zealand Last Glacial Cycle (nzLGM). The climate was cool to cold and while wet in westerly windward locations may have been dry in the east. Combined Australian and New Zealand evidence suggests glacial culmination around 67–62 ka. This regional LGM coincided with severe cooling in Europe.During MIS 3 conditions were very variable. The climate in eastern North Island (Hawke Bay and the Bay of Plenty) at the start of MIS 3 was similar to the Holocene, and the period 61–43 ka was relatively mild overall and is termed the Aurora Interstadial, although it contained a short interval of mountain glacier expansion around 49–47 ka. After 43 ka conditions cooled again with a glacial advance from 42 to 38 ka, before a return to milder but still cool conditions during the Moerangi Interstadial from 37 to 31 ka. After this conditions deteriorated at the lead in to the gLGM. The maximum glacial advance occurred in late MIS 3 between 31 and 29 ka. The glacial onset was abrupt with Te Anau Glacier in Fiordland, one of the largest in the Southern Alps, taking only about 2000 years to achieve its maximum gLGM depth, probably because conditions were wet as well as cold. But stable isotope data suggest that the climate then became drier, while remaining cold, and the glacier progressively ablated such that its surface had lowered 390 m by the start of MIS 2 and by >600 m by ca 18 ka.The gLGM maximum in New Zealand may have led the terrestrial (ice-sheet) LGM in the Northern Hemisphere by a few thousand years, possibly because alpine glaciers respond more rapidly to climate change than continental ice sheets. The culmination of the gLGM in NZ occurred in MIS 3 about 12 000 years before global ice volume reached its peak as determined by the marine stable isotope record (the marine gLGM). By the time global ice volume was at a maximum (19 ka) glaciers had almost disappeared from major Fiordland valleys in New Zealand. Whereas polar ice sheet records have revealed a “bi-polar see-saw”, this is not so evident in the mid-latitudes, because some temperate zone inter-hemispheric climate events coincide closely in time. Perhaps the see-saw effect diminishes with distance from the poles?