期刊
CLIMATE DYNAMICS
卷 45, 期 11-12, 页码 3623-3633出版社
SPRINGER
DOI: 10.1007/s00382-015-2561-x
关键词
Little Ice Age; Volcanic forcing; Last millennium; Horizontal visibility graphs; Time series irreversibility; Marine sediments; Tipping element
资金
- Deutsche Bundesstiftung Umwelt
- Stordalen Foundation
- Potsdam Institute for Climate Impact Research (PIK)
- German Federal Ministry for Science and Education (Project CoSy-CC2) [01LN1306A]
- German Federal Ministry for Science and Education (Project GLUES)
A prominent characteristic of the reconstructed Northern Hemisphere temperature signal over the last millennium is the transition from the Medieval Climate Anomaly to the Little Ice Age (LIA). Here we report indications for a non-linear regime shift in the North Atlantic ocean circulation at the onset of the LIA. Specifically, we apply a novel statistical test based on horizontal visibility graphs to two ocean sediment August sea-surface temperature records from the Norwegian Sea and the central subpolar basin and find robust indications of time-irreversibility in both records during the LIA onset. Despite a basin-wide cooling trend, we report an anomalous warming in the central subpolar basin during the LIA that is reproduced in ensemble simulations with the climate model of intermediate complexity CLIMBER-3 as a result of a non-linear regime shift in the subpolar North Atlantic ocean circulation. The identified volcanically triggered non-linear transition in the model simulations provides a plausible explanation for the signatures of time-irreversibility found in the ocean sediment records. Our findings indicate a potential multi-stability of the North Atlantic ocean circulation and its importance for regional climate change on centennial time scales.
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