The Last Glacial Maximum in central North Island, New Zealand: palaeoclimate inferences from glacier modelling

Quantitative palaeoclimate reconstructions provide data for evaluating the mechanisms of past, natural climate variability. Geometries of former mountain glaciers constrained by moraine mapping afford the opportunity to reconstruct palaeoclimate, due to the close relationship between ice extent and local climate. In this study, we present results from a series of experiments using a 2D coupled energy-balance/ice-flow model that investigate the palaeoclimate significance of Last Glacial Maximum moraines within nine catchments in central North Island, New Zealand. We find that the former ice limits can be simulated when present day temperatures are reduced by between 4 °C and 7 °C, when precipitation remains unchanged from present. The spread in the results between the nine catchments is likely to represent the combination of chronological and model uncertainties. The temperature decrease required to simulate the former glaciers falls in the range of 5.1 °C and 6.3 °C for the majority of catchments targeted, which represents our best estimate of the peak temperature anomaly in central North Island, New Zealand during the Last Glacial Maximum. A decrease in precipitation, as suggested by proxy evidence and climate models, of up to 25 % from present, increases the magnitude of the required temperature changes by up to 0.8 °C. Glacier model experiments using reconstructed topographies that exclude the volume of post-glacial (