Significance Antarctic ice cores provide a precise, well-dated history of increasing atmospheric CO ₂ during the last glacial to interglacial transition. However, the mechanisms that drive the increase remain unclear. Here we reconstruct a key indicator of the sources of atmospheric CO ₂ by measuring the stable isotopic composition of CO ₂ in samples spanning the period from 22,000 to 11,000 years ago from Taylor Glacier, Antarctica. Improvements in precision and resolution allow us to fingerprint CO ₂ sources on the centennial scale. The data reveal two intervals of rapid CO ₂ rise that are plausibly driven by sources from land carbon (at 16.3 and 12.9 ka) and two others that appear fundamentally different and likely reflect a combination of sources (at 14.6 and 11.5 ka).