Last Glacial pollen–climate reconstructions from Northland, New Zealand

Abstract

ABSTRACTDespite wide‐ranging interest in the vegetation and climate of Northland, New Zealand, during the last glacial cycle, the region and timeframe lack quantitative climate reconstructions while land‐based pollen records have tended to be poorly dated and fragmentary. The region is also important for geochronology due to the co‐occurrence of the Rotoehu tephra, a widely dispersed isochron near the current limits of radiocarbon dating, and extensive subfossil wood remains of Agathis australis, with strong dendrochronological and dendroclimatological potential. We present new pollen records and temperature reconstructions from three sites set in coastal dune belts from western mid‐Northland (∼35°S), all containing Rotoehu tephra, that collectively span the last 70 ka. The phases and amplitude of temperature changes broadly align with those reported from elsewhere in New Zealand and with marine isotope climate–stratigraphic records, including maximum temperature depression of 6–8 °C during the last glacial maximum. We argue that these climatic patterns are intimately linked to shifts in the southern westerly wind belt, the northern margins of which extend to the region today. Correspondence between the Northland temperature shifts and atmospheric CO2 supports the model of ocean–atmosphere CO2 flux modulated by latitudinal migration of the southern westerlies. Copyright © 2017 John Wiley & Sons, Ltd.