Decadal warming events extended into central North America during the last glacial period

The connection between abrupt high-latitude warming during the last glacial period—Dansgaard–Oeschger (DO) events—and rapid climate changes at lower latitudes has revealed inter-hemispheric teleconnections in the ocean–atmosphere system. Links between DO events and climate variability in mid-latitude, mid-continent settings remain, however, poorly understood, especially in North America where climate archives with sufficient time resolution are scarce. Here we examine a speleothem that grew from ~70–50 thousand years ago (ka) in Wisconsin (United States) and combine fluorescent imaging of its growth banding with an annual-resolution oxygen isotope (δ 18 O) record. Eight large (2.0–3.0‰) negative δ 18 O excursions, each with an onset in 10 °C in 10 °C occurred repeatedly during the last glacial period in central North America, probably coinciding with Dansgaard–Oeschger warming events, according to an annually resolved speleothem oxygen isotope record and palaeoclimate simulations.