Synchronous volcanic eruptions and abrupt climate change ∼17.7 ka plausibly linked by stratospheric ozone depletion

Abstract

Glacial-state greenhouse gas concentrations and Southern Hemisphere climate conditions persisted until ∼17.7 ka, when a nearly synchronous acceleration in deglaciation was recorded in paleoclimate proxies in large parts of the Southern Hemisphere, with many changes ascribed to a sudden poleward shift in the Southern Hemisphere westerlies and subsequent climate impacts. We used high-resolution chemical measurements in the West Antarctic Ice Sheet Divide, Byrd, and other ice cores to document a unique, ∼192-y series of halogen-rich volcanic eruptions exactly at the start of accelerated deglaciation, with tephra identifying the nearby Mount Takahe volcano as the source. Extensive fallout from these massive eruptions has been found >2,800 km from Mount Takahe. Sulfur isotope anomalies and marked decreases in ice core bromine consistent with increased surface UV radiation indicate that the eruptions led to stratospheric ozone depletion. Rather than a highly improbable coincidence, circulation and climate changes extending from the Antarctic Peninsula to the subtropics-similar to those associated with modern stratospheric ozone depletion over Antarctica-plausibly link the Mount Takahe eruptions to the onset of accelerated Southern Hemisphere deglaciation ∼17.7 ka.

Keywords: aerosol; climate; deglaciation; ozone; volcanism.

Fig. 1.

Changes in climate indicators during the last glacial termination relative to the 17.7 ka glaciochemical anomaly. Shading shows the ∼192-y glaciochemical anomaly. (A) Annually integrated (12) 65°S insolation and (B) WD δ¹⁸O (12); (C) WD CO₂ (15) and (D) Taylor Glacier δ¹³C of CO₂ synchronized to the WD CO₂ record (46); (E) WD CH₄ (60) and (F) WD mineral acidity; SH dust proxies (G) nssCa in the WD core, (H) Ca in the European Project for Ice Coring in Antarctica Dome C (EDC) (11) synchronized to WD using volcanic events, and (I) Fe in a South Australian ocean sediment core (9); (J) the surface UV indicator Br in the WD core; and (K) Botuvera speleothem δ¹⁸O that is a proxy for summertime precipitation in southeastern Brazil (8).

Fig. 2.

Selected high-resolution elemental and gas phase measurements through the ∼192-y glaciochemical anomaly in the WD ice core at 17.7 ka (gray shading) showing nine distinct pulses. Acidity, low-boiling-point heavy metals (e.g., Bi), and halogens (e.g., Cl) other than Br (Fig. 1) were highly elevated throughout the anomaly (SI Appendix, Fig. S1), with REE (e.g., Ce) enhanced only during the first ∼120 y. SH dust indicators (e.g., nssCa) were elevated only slightly, and slowly increasing greenhouse gas [CH₄ (60), CO₂ (15)] concentrations accelerated during the event (Fig. 1). Measurements in the Byrd core are similar (SI Appendix, Fig. S2). Calculated break points (1σ uncertainty) suggest that long-term changes in nssCa, CH₄, and CO₂ concentrations in the WD core began during the 17.7 ka anomaly (Materials and Methods).

Fig. 3.

Spatial extent of the glaciochemical anomaly. Evidence of the ∼192-y anomaly has been found >2,800 km from Mount Takahe in ice core (circles) chemical records (SI Appendix, Fig. S3) as well as radar surveys from much of West Antarctica. Also shown are area volcanoes (triangles). September/October horizontal wind vectors at 600 hPa based on 1981–2010 National Centers for Environmental Prediction reanalysis fields show transport patterns consistent with observations.

Fig. 4.

Sulfur isotope anomalies indicate changes in UV radiation during the 17.7 ka event. Despite relatively modest increases in sulfur concentration in both the WD and Byrd records, volcanic sulfur emissions led to decreased δ³⁴S, while increased UV radiation resulted in anomalous Δ³³S. Uncertainties are 2σ.

Fig. 5.

Observed and modeled SH precipitation anomalies linked to modern stratospheric ozone depletion. Shown are observed and modeled zonal mean austral summer (DJF) net precipitation changes between 1979 and 2000 (37). Changes represent a ∼10% increase between 15°S and 35°S relative to the climatology (37). Simulated LGM responses to stratospheric ozone depletion are qualitatively similar (SI Appendix, AOGCM Simulations). Approximate latitude ranges for SH aridity and glacial outwash dust sources as well as wetlands during the LGM are indicated. Sharp changes in SH climate proxies occur exactly at this time (4, 6, 7, 10, 11, 14) (Fig. 1).