THE LAST DEGLACIATION IN NEW ZEALAND; LOCAL MANIFESTATIONS OF GLOBAL SIGNALS

The New Zealand region is recognized as a critical region for understanding global paleoclimatology, because it is a prime location to examine the Southern Hemisphere westerly circulation, which is the interface between the Antarctic and the rest of the global circulation. It has become a major focus for inter-hemispheric climatic teleconnection studies.

Much effort has gone into reconstructing the Last Termination in New Zealand, but the results are contradictory. Biological proxy evidence has consistently failed to reproduce Northern Hemisphere (or more precisely North Atlantic) patterns. Most pollen records yield either a monotonic climatic amelioration during the deglaciation, or a two step deglaciation, with the first warming phase completed by 14 ka and the second initiated after 11.5 ka. They do not support simple trans-hemispheric teleconnections. Marine records from the New Zealand shelf show an Antarctic Cold Reversal (ACR) signal but no Younger Dryas (YD) chron signal. In contrast, there is unambiguous evidence for a major glacial re-advance at, or very close, to the YD chron, but no ACR signal.

We present a high resolution (probably annual) record of change from a Maar lake the Auckland region, New Zealand. This record has been analysed spectrally for three time intervals; an eight hundred year period just prior to the last glaciation maximum, two thousand years during the deglaciation and a three hundred and fifty year period during the early Holocene. Strong spectral power in 2-7 year, 15-20 year and a centennial (80-120 year) timescale during two brief intervals during the deglaciation contrasts with virtually no spectral power during the rest of the deglaciation. The ACR appears to be the younger (and stronger) deglacial event. In contrast, the YD is not defined in these records.

The results indicate that El Nino Southern Oscillation (ENSO) and the Pacific decadal oscillation (PDO), two of the primary drivers of modern New Zealand climate, pulsed on and off during the deglaciation. Under modern conditions ENSO and PDO are strongly associated with modification of south-westerly flow over northern New Zealand and we infer enhanced westerly flow over New Zealand during the two deglaciation spectral events. The implications of these findings for global climate teleconnections will be discussed.