Ice core evidence for major volcanic eruptions at the onset of Dansgaard-Oeschger warming events

• Main Authors: Lohmann, Johannes, Svensson, Anders
• Format: Text
• Language: English
• Published: 2022
• Subjects: geo; envir; Antarctic; Greenland; Antarc*; Dansgaard-Oeschger events; ice core; North Atlantic
• Online Access: https://doi.org/10.5194/cp-2022-1; https://cp.copernicus.org/preprints/cp-2022-1/

A significant influence of major volcanic eruptions on regime shifts and long-term climate variability has been suggested previously. But a statistical assessment of this has been hampered by inaccurate synchronization of large volcanic eruptions to changes in past climate. Here, this is achieved by combining a new record of bipolar volcanism from Greenland and Antarctic ice cores with records of abrupt climate change derived from the same ice cores. We show that bipolar volcanic eruptions occurred significantly more frequently than expected by chance just before the onset of Dansgaard-Oeschger events, the most prominent large-scale abrupt climate changes of the last glacial period. Out of 20 abrupt warming events in the 12–60 ka period, 5 (7) occur within 20 (50) years after a bipolar eruption. A similar statistical relationship is not found for eruptions before the abrupt cooling phases of the Dansgaard-Oeschger cycles. We hypothesize that this asymmetric response to volcanic eruptions may be a result of the direct influence of volcanic cooling on the Atlantic meridional overturning circulation, which is widely regarded as the main climate subsystem involved in Dansgaard-Oeschger cycles. Transitions from a weak to a strong circulation mode, but not vice versa, may be triggered by cooling in the North Atlantic, given the circulation is close to a stability threshold. We illustrate this suggestion by simulations with a global ocean model forced by short-term volcanic cooling. The analysis presented suggests that large eruptions may act as short-term triggers for large-scale abrupt climate change, and may explain part of the variability of Dansgaard-Oeschger cycles.