North Atlantic drivers of Southern Hemisphere rainfall: A high-resolution speleothem record from Waipuna Cave, New Zealand.

During the Last Glacial Period, Earth was characterised by rapid millennial-scale climate oscillations, known as ‘Dansgaard–Oeschger’ (D-O) events, associated with large-scale reorganisations of oceanic and atmospheric circulation. While such variability is well documented in Northern Hemisphere high-latitude archives, such as Greenland ice cores, its expression remains less constrained in the Southern Hemisphere mid-latitude, raising the question of whether these climate disturbances, initiated in the North Atlantic Ocean, influenced rainfall patterns thousands of kilometres away in the Southern Hemisphere’s Southwest Pacific.

Here we present a new high-resolution speleothem composite record from Waipuna Cave (North Island, New Zealand), integrating two cores from the same flowstone aligned using a dynamic time warping approach. The composite spans 36.2–11.1 thousand years before present, and is constrained by 61 U–Th ages, yielding a mean age uncertainty of ~250 years (2σ). Combined stable isotope (δ¹⁸O, δ¹³C) and trace element (Mg/Ca) profiles provide a multiproxy record of hydroclimatic variability at  Southern Hemisphere mid-latitudes.

The Waipuna record reveals rapid millennial-scale variability that resembles Dansgaard–Oeschger (DO) events. Periods of reduced regional water balance (precipitation minus evapotranspiration) on New Zealand’s northwest coast are consistent with large-scale atmospheric and oceanic reorganizations involving a shift of the rainfall belt, or the Intertropical Convergence Zone (ITCZ), and modulation of the Southern Westerly Winds. Comparison with well-dated, monsoon-sensitive speleothem records from equatorial to subtropical latitudes suggests that the Waipuna hydroclimate variability forms part of a broader pattern of global atmospheric reorganisation.

These results highlight the sensitivity of the Southwest Pacific mid-latitude hydroclimate to the large-scale atmospheric circulation changes during the last glacial period and emphasize the importance of the Southern Hemisphere records for constraining the understanding of the interhemispheric climate coupling. In the context of ongoing climate change, such past analogues may inform future shifts in subtropical rainfall distribution and extreme precipitation events.

Keywords: Last Glacial Period, Speleothem, New Zealand, Interhemispheric teleconnections.