Fig. 4: Simulated hydroclimate changes during DO warmings.

a Modeled AMOC index defined by the maximum stream function between 500–2500 m in the North Atlantic north of 45°N in the self-oscillatory AMOC equilibrium experiment (E40ka_34Orb in ref. ⁵³). We classify three AMOC phases: Stadial phases, Overshoot phases and Interstadial phases (Methods). Also shown is the modeled NGRIP mean annual δ¹⁸O_p. Both time series were averaged using a 30-year running window. b Composites of changes in mean annual δ¹⁸O_p over continents and mean annual δ¹⁸O of sea-surface water (δ¹⁸O_sw) over oceans (shaded, units: ‰) and vertical integrated water-vapor transport (WT) (vectors, units: kg/m/s) during simulated short (Overshoot minus Stadial phases) warming events, (c) same as (b) but for differences between simulated long and short (Interstadial minus Overshoot phases) interstadials. Note that the color scales and wind vectors in (b) and (c) are different. d Impact of the Northern Westerlies on interstadial ASM δ¹⁸O_p variations, expressed as the ratio of δ¹⁸O_p changes: (Interstadial minus Overshoot phases)/(Interstadial minus Stadial phases). In the core ASM domain, positive values denote regions with influences of the Westerlies shifts. The values of the ratio approaching 1 indicate a muted δ¹⁸O_p depletion during transitions from stadial to short interstadials and to overshoot phases of long interstadials, as a consequence of a further northward shift in Northern Westerlies. Ratios near zero indicate δ¹⁸O_p differences between interstadials and stadials are independent of the Westerlies shift. Bittoo, Xinglong, Xiaotian, Qixing, Shennong and Xianyun cave locations are indicated by the yellow stars (refer to Fig. 1d). The thick black line delineates the approximate region of the EASM and ISM and the transitional zone between them, as same as in Fig. 1d. ASM Asian summer monsoon; ISM Indian summer monsoon; EASM East Asian summer monsoon. DO Dansgaard-Oeschger.