Regional climate regime classification as a qualitative tool for interpreting multi-proxy palaeoclimate data spatial patterns: A New Zealand case study

The precipitation characteristics of three basic circulation types for New Zealand weather [Kidson, J.W. 2000. An analysis of New Zealand synoptic types and their use in defining weather regimes. International Journal of Climatology. 20, 299–316] are explored here as a palaeoclimate reconstruction tool, and are utilised as a way to interpret spatial patterns exhibited by diverse multi-proxy data assemblages. The technique is founded on a modern climate shift analogue for New Zealand where regional precipitation spatial changes accompanied the 1976/77 Inter-decadal Pacific Oscillation (IPO) phase change. The analysis here indicates multi-decadal-scale circulation changes (both in frequency and strength) resulted from the 1976/77 IPO phase change primarily during mid–late summer, late autumn and late winter, and a significant change (a zonal regime frequency and strength increase) occurred for August. From the climatological results, the eastern North Island along with the western and eastern South Island are crucial regions to include in a spatial pattern-based palaeoclimate reconstruction because of sensitivities to zonal circulation changes. Ascribing a climate regime classification to multi-proxy data was subsequently attempted for three discrete timeslices in the Late Holocene, and illustrates that many different types of multi-proxy terrestrial data can successfully be assimilated with some evident advantages and shortcomings. Climate regime classification has good potential for highlighting spatial and temporal gaps in regional palaeoclimate proxy networks, and in the case of New Zealand, potential for connecting local and regional palaeoclimate data to conditions associated with westerly circulation changes, the IPO, and for exploration of Australasian and extra-tropical palaeoclimate archive connections.