Fig. 4: Top panel: OS stalagmite oxygen (blue) and carbon (green) isotope records.

Darker overlay lines are running averages with a resolution of 50 years. OS isotopic records cover the interval from 17.6 to 14.3 kyrs BP. Timing of Heinrich event 1 and distinct peaks in ice-rafted detritus (IRD) of Heinrich Layer 1 (from ref. ⁴), as well as the Bølling–Allerød (B/A) warm interval, are shown on the plot (blue and orange bars, respectively). Mean of both δ¹⁸O and δ¹³C records are denoted with a solid black line. Data symbols are red shaded if higher than the mean (drier), and blue shaded if lower than the mean (wetter). Lower panel: wavelet spectral power analyses of OS oxygen isotope record. Higher intensity of the color is indicating more power over a specific periodicity range within that same time interval. This indicates that periodicity range in particular (e.g., 8 years) is more strongly represented in the timeseries. The area outside the white curves indicates the cone of influence where the edge effects of the wavelet transform and uncertainties become important. Black contours reflect statistically significant power spectra (CI = 95%) (see Methods and Supplementary (page 6) for details).