PP43F-06
Hydroclimate variability and regional atmospheric circulation over the past 1,350 years reconstructed from Lake Ohau, New Zealand

Thursday, 17 December 2015: 14:55
2003 (Moscone West)
Heidi A Roop1,2, Richard H Levy3, Marcus Vandergoes3, Gavin B Dunbar2, Jamie D Howarth1 and Andrew Lorrey4, (1)GNS Science-Institute of Geological and Nuclear Sciences Ltd, Lower Hutt, New Zealand, (2)Victoria University of Wellington, Antarctic Research Centre, Wellington, New Zealand, (3)GNS Science, Lower Hutt, New Zealand, (4)NIWA National Institute of Water and Atmospheric Research, Auckland, New Zealand
Abstract:
Comprehensive understanding of natural climate-system dynamics requires high-resolution paleoclimate records extending beyond the instrumental period. This is particularly the case for the sparsely-instrumented Southern Hemisphere mid-latitudes, where the timing and amplitude of regional and hemispheric-scale climatic events are poorly constrained.

Here we present a 1,350-year record of hydroclimatic variability and regional circulation derived from an annually laminated sediment record from Lake Ohau, South Island, New Zealand (44.23°S, 169.85°E). The climate of New Zealand is influenced by climatological patterns originating in both the tropics (e.g. El-Niño-Southern Oscillation, Interdecadal Pacific Oscillation) and the Antarctic (Southern Annular Mode, SAM). Utilizing the annually resolved Lake Ohau hydroclimate record in combination with a tree-ring record of summer temperature from Oroko Swamp, New Zealand (Cook et al., 2002), we generate a circulation index for the Western South Island of New Zealand. This index utilizes the temperature and precipitation anomalies defined by the Regional Climate Regime Classification scheme for New Zealand (Kidson, 2000) to assign synoptic scale circulation patterns to 25-year intervals from 900-2000 AD. This circulation index shows significant periods of change, most notably 835 – 985 AD when northerly airflow dominated and from 1385 – 1710 AD when strong southerly airflow persisted. Comparisons with regional SAM and ENSO reconstructions show that dry, warm conditions at Lake Ohau are consistently associated with strengthened tropical teleconnections to New Zealand and a positive SAM, while cold and wet conditions are driven by increased southerly airflow and negative phase SAM. A persistent negative SAM dominates the Little Ice Age (LIA; ~1385-1710 AD) interval in the Western South Island. This same period coincides with the Northern Hemisphere LIA.

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