Millennial-scale periodicities associated with changes in wind ansd precipitation over the last Glacial cycle (ca. 117 ± 8.5 ka BP) recorded in sediments from Lake Kai Iwi, Northland, New Zealand

Abstract

Mid-latitude Southern Hemisphere proxy records of changing environment, especially those that demonstrate past variability of the South Westerly Winds (SWW), are poorly-constrained prior to the Last Glacial Interglacial Transition (LGIT; ca. 14–11.7 ka BP) and are typically located far enough south or north that they often do not reflect both tropical and SWW signals. With this deficiency in mind, we present a ca. 117 ± 8.5 ka BP lake sediment record from Lake Kai Iwi, Northland, New Zealand (~36°S), located at a latitude that demonstrates changes in precipitation associated with both the northward expansion of the SWW belt and from tropical El Niño Southern Oscillation (ENSO) variability. We converted Lake Kai Iwi μ-XRF proxy data to even time-steps in order to apply Morelet wavelet analysis for identification of millennial-scale periodicities in the data that were likely driven by orbital forcing. The results indicate that Lake Kai Iwi records a ~1 ka periodicity possibly associated with Northern Hemisphere ice sheet dynamics; a ~2–4 ka periodicity associated with ~2.4 ka Hallstatt solar cycles, and a ~9 ka periodicity linked to CO2 outgassing from upwelling in the Southern Ocean driven by changes in intensity and position of the SWW.