Palaeocirculation across New Zealand during the last glacial maximum at w21 ka Andrew M. Lorrey a, * , Marcus Vandergoes b , Peter Almond c , James Renwick d , Tom Stephens e , Helen Bostock d , Andrew Mackintosh f , Rewi Newnham f , Paul W. Williams e , Duncan Ackerley d , Helen Neil d , Anthony M. Fowler e a National Institute of Water and Atmospheric Research, Private Bag 99940, 41 Market Place, Auckland 1010, New Zealand b Institute of Geological and Nuclear Sciences, Lower Hutt, New Zealand c Lincoln University, Faculty of Agriculture and Life Science, Lincoln, Canterbury, New Zealand d National Institute of Water and Atmospheric Research, Wellington, New Zealand e University of Auckland, School for the Environment, Private Bag 92019, Auckland, New Zealand f Victoria University Wellington, School of Geography, Environment and Earth Sciences, Wellington, New Zealand article info Article history: Received 14 April 2011 Received in revised form 29 September 2011 Accepted 30 September 2011 Available online 24 October 2011 Keywords: New Zealand Palaeoclimate LGM Atmospheric circulation Regional climate regime classification Multi-proxy NZ-INTIMATE abstract What circulation pattern drove Southern Alps glacial advances at w21 ka? Late 20th century glacial advances in New Zealand are commonly attributed to a dual precipitation increase and cooler than normal temperatures associated with enhanced westerly flow that occur under synoptic pressure patterns termed ‘zonal’ regimes (Kidson, 2000). But was the circulation pattern that supported major Southern Alps glacial advances during the global LGM similar to the modern analog? Here, a Regional Climate Regime Classification (RCRC) time slice was used to infer past circulation for New Zealand during the LGM at w21 ka. Palaeoclimate information that supported the construction of the w21 ka time slice was derived from the NZ-INTIMATE Climate Event Stratigraphy (CES), one new Auckland maar proxy record, and additional low-resolution data sourced from the literature. The terrestrial evidence at w21 ka implicates several possibilities for past circulation, depending on how interpretations for some proxies are made. The interpretation considered most tenable for the LGM, based on the agreement between terrestrial evidence, marine reconstructions and palaeoclimate model results is an ‘anticyclonic/zonal’ circulation regime characterized by increased influences from blocking ‘highs’ over the South Island during winter and an increase in zonal and trough synoptic types (with southerly to westerly quarter wind flow) during summer. These seasonal circulation traits would have generated lower mean annual temperatures, cooler than normal summer temperatures, and overall lower mean annual precipitation for New Zealand (particularly in the western South Island) at w21 ka. The anticyclonic/zonal time slice reconstruction presented in this study has different spatial traits than the late 20th Century and the early Little Ice Age signatures, suggesting more than one type of regional circulation pattern can drive Southern Alps glacial activity. This finding lends support to the hypothesis that temperature over precipitation change is more important as the primary modulator of Southern Alps ice advances. The RCRC approach also demonstrates some subtle advantages of integrating multi- proxy data within a palaeocirculation context for New Zealand, notably because this reconstruction technique enables direct comparisons to coarsely resolved palaeoclimate model outputs that do not have downscaled information. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction 1.1. Background The global last glacial maximum (referred to as the LGM) is recognised as a cold period during the last glacial-interglacial cycle that was fundamental to Late Quaternary environmental changes across the Earth. Abundant attention has been devoted to Northern Hemisphere LGM terrestrial and marine climate recon- structions that coincided with maximally expanded Eurasian and Laurentide Ice Sheets. However in the Southern Hemisphere, particularly in the land-sparse Southwest Pacific mid-latitudes, few areas supported glacier growth during the LGM (see Ehlers and Gibbard, 2004 for basic overview of glaciated Australasian regions). New Zealand is one of few exceptions in the ‘water * Corresponding author. Tel.: þ64 9 375 2055; fax: þ64 9 375 2051. E-mail address: a.lorrey@niwa.co.nz (A.M. Lorrey). Contents lists available at SciVerse ScienceDirect Quaternary Science Reviews journal homepage: www.elsevier.com/locate/quascirev 0277-3791/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.quascirev.2011.09.025 Quaternary Science Reviews 36 (2012) 189e213