Millennial-scale glacier fluctuations in southern New Zealand during the past 200 ka

Glacials and interglacials characterized the Quaternary period and were caused by global and regional climate fluctuations. The advances and retreats of glaciers in New Zealand’s Southern Alps during the Late Quaternary can be attributed to global climate fluctuations in conjunction with the adjacent surface ocean dynamics and interactions with the southern westerly wind belt. Several studies have been conducted to better understand the role of New Zealand’s climate in the Quaternary ice age cycles, mostly focusing on the last glacial period that is well covered by regional climate archives. However, marine sediment cores can be used as continuous archives for glacier fluctuations over several of the past glacial-interglacial cycles. The present study investigates the glaciation history of New Zealand’s South Island over the last 200,000 years and its interaction with paleoceanographic changes of the adjacent Southeast Tasman Sea. South of New Zealand, Solander Trough is located under the Subtropical Frontal Zone (STFZ) that separates warm subtropical waters from cold subantarctic waters. During glacial periods, the STFZ shifted equatorward. Core SO290-17-1 from Solander Trough was dated using oxygen isotopes from benthic foraminifera as well as paleo- and rock-magnetic measurements in combination with x-ray fluorescence (XRF) core scanning data and aligning them to a well-dated neighboring sediment core (TAN1106-28; Toucanne et al., 2026) covering the last glacial period. n-alkane biomarkers were used to investigate terrigenous input and vegetation changes, whereas C₃₇ alkenones (U^K’₃₇) were used to estimate sea-surface temperatures (SST). These data are compared to the Ti/K ratio and terrigenous Nd isotope compositions (expressed as ɛNd) of the sediments as proxies for the source of the terrigenous material and hence glacier fluctuations. The concentration of n-alkanes increases during glacial periods indicating terrestrial organic matter input. The Ti/K ratio shows a similar pattern and indicates compositional changes of the terrigenous fraction that are also seen in ɛNd and suggest that during these phases, extensive glaciation occurred in the Southern Alps. The SST anti-correlates with those glacier advances and follows an Antarctic pattern. Changes in SST of ~12°C can be observed between glacial and interglacial periods together with a short-term, millennial variability. Compared to Patagonia, the SST changes more abruptly and with a higher magnitude. Our preliminary results indicate glacier advances during MIS 5b and 5d, which are consistent with the dominance of beech forests from pollen records during these cooler intervals. Furthermore, our data indicate large glacier fluctuations during MIS 6 with three major expansion phases at ~137 ka, ~157 ka and ~178 ka and even more frequent phases of glacier expansions on a millennial scale.

 

References

Toucanne, S., Vázquez Riveiros, N., Soulet, G., Blard, P.-H., Migeon, A., Rigalleau, V., Roubi, A., Cheron, S., Boissier, A., Menviel, L., and Bostock, H.: Synchronous bipolar retreat of mid-latitude ice masses during Heinrich Stadials, Nat. Geosci., 1–6, https://doi.org/10.1038/s41561-025-01887-x, 2026.