Abstract:
Large volcanic eruptions have long been recognised as drivers of climatic and environmental change, such as “volcanic winters”. Speleothems are secondary calcite deposits that form in caves, which provide a record of external environmental conditions. In this study, a New Zealand stalagmite (Te Reinga A [TRA]) was investigated to search for potential chemical and isotopic fingerprints of global volcanic eruptions of late Holocene age, like those that have been recorded in polar ice cores and temperate tree-ring records. U–Th-series dating revealed that in the TRA, the growth period ~1000 CE to ~1950 CE was analysed, with apparent hiatuses at ~1112 ± 5, ~1136 ± 17, ~1186 ± 23, ~ 1285 ± 65, ~1453 ± 67, and ~1801 ± 149 CE. Trace element analysis of TRA by laser ablation inductively coupled plasma mass spectrometry revealed that these hiatuses were associated with distinct periods of short-term geochemical change, particularly for Mg and Sr, as well as speleothem textural changes. Stable Ca isotopic data also revealed changes across these hiatuses. These geochemical and textural anomalies temporally coincide with large global volcanic eruptions identified in the tree-ring and ice core record of Sigl et al. (2015), suggesting these were the likely drivers of these changes. The 1258 CE Samalas, 1458 CE Kuwae, and the 1815 CE Tambora eruptions are notable in the chronology extracted from TRA. Further evidence of the volcanically forced origins for the changes includes excess Tl, a volcanically derived volatile, for some of the anomalies. These results show, for the first time, that global volcanic eruptions have produced major climatic and presumably environmental impacts in New Zealand. The magnitude of these changes due to global volcanic eruptions are apparently more severe than any other climatic factors in the past 1,000 yr, at least for the eastern region of the North Island.
