Fig. 1: High-resolution CO₂ and δ¹³C-CO₂ data from Taylor Glacier.

a Data from this study (red circles) show larger variations in δ¹³C-CO₂ across the transition into and out of Marine Isotope Stage 4 (74–59.5 ka) than preexisting δ¹³C-CO₂ data (white and blue circles) spanning the last two deglaciations (140–125 and 21–11 ka)^{4, 22,23,24} and the Heinrich Stadial (HS)-4/Dansgaard–Oeschger (DO)-8 transition (46–36 ka)²⁶. The large changes in the δ¹³C-CO₂ are surprising given the relatively smaller magnitude changes in CO₂. Mean ocean temperature data derived from ice core noble gas measurements show relatively smaller changes across the MIS 5-4 transition¹² relative to the last two deglaciations^80,81,82. North Greenland Ice Core Project (NGRIP)⁴⁸ and EPICA Dome C (EDC)⁸³ water isotopes are plotted for chronological and climatic reference. b An enlarged plot of the interval 77–55 ka compares Taylor Glacier data to preexisting CO₂ and δ¹³C-CO₂ data from EPICA Dome C (EDC), EPICA Dronning Maud Land (EDML), and Talos Dome ice cores. The interval is divided into four subintervals (I–IV) highlighting distinct modes of change in CO₂ and δ¹³C-CO₂ discussed in the text. Error bars represent 1-sigma analytical uncertainty.