South Pole Ice Core (SPICEcore) Dust Record of Southern Westerly Wind Variability during Dansgaard-Oeschger Events

Dansgaard-Oeschger (DO) events of the last glacial period are the most extreme climate fluctuations recorded in Greenland ice cores, providing dramatic examples of natural abrupt climate change that provide insight to nonlinear climate dynamics. Multi-decadal temperature changes of 5-15°C characterized Greenland's DO transitions between cold "stadial" periods and warm "interstadial" periods. The longest Stage 3 (60-27 ka) stadial events in the Greenland ice core record were coincident with Heinrich Events (hereafter `Henrich stadials'), when armadas of icebergs traversed the North Atlantic Ocean as recorded in marine sediments. While changes in Atlantic Meridional Overturning Circulation (AMOC) can largely account for the muted, out-of-phase DO temperature changes observed in Antarctic ice cores, the signature and impact of atmospheric circulation changes during DO events are poorly constrained. For example, atmospheric CO<sub>2</sub> concentrations increased during Heinrich stadials but not during non-Heinrich stadials, despite similar Antarctic warming during both. Changes in the position and intensity of the southern westerly wind (SWW) belt are likely involved because they can strongly affect carbon flux between the Southern Ocean and the atmosphere. However, the behavior of the SWW during Heinrich and non-Heinrich stadials remains unclear. Here we use the new, high-resolution mineral dust flux record from the South Pole Ice Core (SPICEcore) to infer changes in the SWW position and intensity during Stage 3. We find persistently strong relationships between dust flux and stable water isotopes (hereafter `dust-¹⁸O slope') throughout Stage 3, consistent with prior results (Lambert et al., 2008; Markle et al., 2018). However, the SPICEcore dust-¹⁸O slope during non-Heinrich stadials is significantly different than the slope during Heinrich stadials and the remainder of Stage 3. This evidence indicates that the SWW responded differently during Heinrich and non-Heinrich stadials, potentially reconciling the observed differences in atmospheric CO₂. Our work provides new details about the Southern Hemisphere atmospheric response during DO events, clarifying an essential link in the sequence of events that produced this remarkable climate variability.