The anatomy of long-term warming since 15 ka in New Zealand based on net glacier snowline rise

The timing and magnitude of postglacial climatic changes around the globe provide insights into the underlying drivers of natural climate change. Using geomorphologic mapping of moraines, Be-10 surface-exposure dating, snowline reconstructions, and numerical modeling, we quantified glacier behavior during Late Glacial (15-11.5 ka) and Holocene (the past similar to 11.5 k.y.) time in the Ben Ohau Range, New Zealand. Glaciers were more extensive during the Antarctic Cold Reversal (ACR), than subsequently, and the margins underwent a punctuated net withdrawal over the Holocene. Numerical modeling experiments that achieve the best fit to the moraines suggest that air temperature during the ACR was between 1.8 degrees C and 2.6 degrees C cooler than today, with similar (+/- 20%) prescribed precipitation. After the ACR, a net snowline rise of similar to 100 m through the Younger Dryas stadial (12.9-11.7 ka) was succeeded by a further long-term, or net, rise of similar to 100 m between similar to 11 k.y. and similar to 500 yr ago. Glacier snowline records in New Zealand show generally coherent Late Glacial and Holocene climate trends. However, the paleoclimate record in the southwest Pacific region shows important differences from that in the Northern Hemisphere.