Environmental change recorded in physical and geochemical proxies over the Last Glacial Cycle from two Northland, New Zealand dune lakes: Lake Kanono and Lake Kai Iwi
Lake sediment archives from Southern Hemisphere mid-latitude regions with maritime climates provide invaluable records of late Quaternary environmental change that are essential for the evaluation of inter-annual, decadal, centennial, and millennial-scale trends driven by shifting positions of the Southern Westerly Winds (SWW) and storm belts associated with the Southern Annular Mode (SAM) and El Niño Southern Oscillation (ENSO). Here environmental conditions were reconstructed from lake sediment cores obtained from Lake Kanono and Lake Kai Iwi in Northland, New Zealand. Using a multi-proxy approach incorporating physical, sedimentological, geochemical, and μ-XRF elemental datasets, changes were identified in wind intensity and precipitation that likely correspond to regional and global climatic shifts associated with changes in intensity of the SWW and the appearance and increase in intensity of the ENSO. Principal component analysis (PCA) and cluster analysis were performed on the μ-XRF elemental data set to identify patterns in the μ-XRF proxy data associated with environmental change manifested as changes in precipitation and wind deposition. The Lake Kanono record extends to from ca. 54 – 0 ka BP and shows increasing detrital influx during the drier conditions associated with the global Last Glacial Maximum (LGM) (ca. 24 ka BP) and the Last Glacial Cold Period (LCGP) (ca. 28 ka BP) in New Zealand. The Lake Kanono μ-XRF Holocene data indicates increased detrital influx during both Polynesian and European settlement phases in this part of northern New Zealand. Furthermore, the timing of Polynesian settlement was coeval with changes in ENSO and SAM polarity. The Lake Kai Iwi record has an extrapolated basal age of ca. 117 ka BP and shows increased precipitation associated with warm marine isotope stages (MIS) 1 and 5, and increased aeolian dust influx during the glacial MIS of 2 and 4. The Lake Kai Iwi sediments also demonstrate changes in precipitation associated with both the northward expansion of the SWW belt and from tropical El Niño Southern Oscillation (ENSO) variability. Morelet wavelet analysis of the μ-XRF results indicate periodicities associated with orbital forcing, solar cycles, and CO2 outgassing from upwelling in the Southern Ocean manifested as changes in intensity and position of the SWW.
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