Southern Ocean drives multidecadal atmospheric CO 2 rise during Heinrich Stadials

WENDT, KATHLEEN A.; NEHRBASS-AHLES, CHRISTOPH; NIEZGODA, KYLE; NOONE, DAVID; KALK, MICHAEL; MENVIEL, LAURIE; GOTTSCHALK, JULIA; RAE, JAMES W. B.; SCHMITT, JOCHEN; FISCHER, HUBERTUS; STOCKER, THOMAS F.; MUGLIA, JUAN; FERREIRA, DAVID; MARCOTT, SHAUN A.; BROOK, EDWARD; BUIZERT, CHRISTO

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA

NATL ACAD SCIENCES

Año: 2024 vol. 121

0027-8424

The last glacial period was punctuated by cold intervals in the North Atlantic regionthat culminated in extensive iceberg discharge events. These cold intervals, known asHeinrich Stadials, are associated with abrupt climate shifts worldwide. Here, we presentCO 2 measurements from the West Antarctic Ice Sheet Divide ice core across HeinrichStadials 2 to 5 at decadal-­ scale resolution. Our results reveal multi-­ decadal-­ scale jumpsin atmospheric CO 2 concentrations within each Heinrich Stadial. The largest magnitudeof change (14.0 ± 0.8 ppm within 55 ± 10 y) occurred during Heinrich Stadial 4. Abruptrises in atmospheric CO 2 are concurrent with jumps in atmospheric CH 4 and abruptchanges in the water isotopologs in multiple Antarctic ice cores, the latter of which sug-gest rapid warming of both Antarctica and Southern Ocean vapor source regions. Thesynchroneity of these rapid shifts points to wind-­ driven upwelling of relatively warm,carbon-­ rich waters in the Southern Ocean, likely linked to a poleward intensificationof the Southern Hemisphere westerly winds. Using an isotope-­ enabled atmosphericcirculation model, we show that observed changes in Antarctic water isotopologs canbe explained by abrupt and widespread Southern Ocean warming. Our work presentsevidence for a multi-­ decadal-­ to century-­ scale response of the Southern Ocean to changesin atmospheric circulation, demonstrating the potential for dynamic changes in SouthernOcean biogeochemistry and circulation on human timescales. Furthermore, it suggeststhat anthropogenic CO 2 uptake in the Southern Ocean may weaken with polewardstrengthening westerlies today and into the future.