A 1,200-year record of climate variability reconstructed from a laminated lacustrine sediment sequence from Lake Ohau, South Island, 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 is poorly constrained. 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). Specifically, summer rainfall records from the western South Island of New Zealand exhibit decadal trends that are highly correlated with the SAM.

A 1,200-year laminated sediment sequence recovered from Lake Ohau (44.234°S, 169.854°E), which sits in this SAM-sensitive region of New Zealand, offers a unique opportunity to explore the hydrology and climate of this region at annual-to-decadal resolution. Here we present a climate-proxy model based on detailed micro-facies analysis, physical (particle size, porosity) and chemical (ITRAX micro-XRF) characteristics of the lamination stratigraphy, and an 85-year hydrometeorological record. Using this model, we explore climate trends over the last 1,200 years and compare this sediment record to SAM reconstructions from paleoclimate model simulations, and South American tree ring and Antarctic ice core proxy records.