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The last glacial period was punctuated by cold intervals in the North Atlantic region that culminated in extensive iceberg discharge events. These cold intervals, known as Heinrich Stadials, are associated with abrupt climate shifts worldwide. Here, we present CO₂measurements from the West Antarctic Ice Sheet Divide ice core across Heinrich Stadials 2 to 5 at decadal-scale resolution. Our results reveal multi-decadal-scale jumps in atmospheric CO₂concentrations within each Heinrich Stadial. The largest magnitude of change (14.0 ± 0.8 ppm within 55 ± 10 y) occurred during Heinrich Stadial 4. Abrupt rises in atmospheric CO₂are concurrent with jumps in atmospheric CH₄and abrupt changes in the water isotopologs in multiple Antarctic ice cores, the latter of which suggest rapid warming of both Antarctica and Southern Ocean vapor source regions. The synchroneity of these rapid shifts points to wind-driven upwelling of relatively warm, carbon-rich waters in the Southern Ocean, likely linked to a poleward intensification of the Southern Hemisphere westerly winds. Using an isotope-enabled atmospheric circulation model, we show that observed changes in Antarctic water isotopologs can be explained by abrupt and widespread Southern Ocean warming. Our work presents evidence for a multi-decadal- to century-scale response of the Southern Ocean to changes in atmospheric circulation, demonstrating the potential for dynamic changes in Southern Ocean biogeochemistry and circulation on human timescales. Furthermore, it suggests that anthropogenic CO₂uptake in the Southern Ocean may weaken with poleward strengthening westerlies today and into the future. 

This data set contains measurements of carbon dioxide (CO2) amount fractions in gas bubbles from the WAIS Divide ice core WD06. All measurements were made in the Ice Core Laboratory at Oregon State University in Corvallis, Oregon USA. The data set includes the replicate-mean values and measurement precision (1 sigma standard error) from all CO2 measurements published in Wendt et al. (2024) PNAS. Bauska et al. (2021) Nature Geoscience, and Marcott et al. (2014) Nature. See respective publications for details. Ages listed in years before 1950 AD on the WD2014 timescale (see Buizert et al., 2015 and Sigl et al., 2014 for chronology details).