Do terrestrial geomagnetic field reversals have an effect on Earth's climate? Cooper et al. created a precisely dated radiocarbon record around the time of the Laschamps geomagnetic reversal about 41,000 years ago from the rings of New Zealand swamp kauri trees. This record reveals a substantial increase in the carbon-14 content of the atmosphere culminating during the period of weakening magnetic field strength preceding the polarity switch. The authors modeled the consequences of this event and concluded that the geomagnetic field minimum caused substantial changes in atmospheric ozone concentration that drove synchronous global climate and environmental shifts.Science, this issue p. 811Geological archives record multiple reversals of Earth’s magnetic poles, but the global impacts of these events, if any, remain unclear. Uncertain radiocarbon calibration has limited investigation of the potential effects of the last major magnetic inversion, known as the Laschamps Excursion [41 to 42 thousand years ago (ka)]. We use ancient New Zealand kauri trees (Agathis australis) to develop a detailed record of atmospheric radiocarbon levels across the Laschamps Excursion. We precisely characterize the geomagnetic reversal and perform global chemistry-climate modeling and detailed radiocarbon dating of paleoenvironmental records to investigate impacts. We find that geomagnetic field minima ~42 ka, in combination with Grand Solar Minima, caused substantial changes in atmospheric ozone concentration and circulation, driving synchronous global climate shifts that caused major environmental changes, extinction events, and transformations in the archaeological record.
Funding: We thank the Australian Research Council for Discovery Grant and Laureate Fellowship support [DP170104665 and FL140100260 (A.C.) and FL100100195 (C.S.M.T.)], the University of Adelaide Environment Institute, the Australasian Antarctic Expedition 2013?2014 and The Tiama, the Royal Society of New Zealand Marsden Fund (contract MFPNIW1803), NIWA, the University of Waikato, the Leverhulme Trust (RF-2019-140\9), the Russian Science Foundation (20-67-46016), and a Swiss National Science Foundation Ambizione grant (PZ00P2_180043).
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- Journal Article
- Research Support, Non-U.S. Gov't