Timing and structure of the Younger Dryas event and its underlying climate dynamics

Abstract

The Younger Dryas (YD), arguably the most widely studied millennial-scale extreme climate event, was characterized by diverse hydroclimate shifts globally and severe cooling at high northern latitudes that abruptly punctuated the warming trend from the last glacial to the present interglacial. To date, a precise understanding of its trigger, propagation, and termination remains elusive. Here, we present speleothem oxygen-isotope data that, in concert with other proxy records, allow us to quantify the timing of the YD onset and termination at an unprecedented subcentennial temporal precision across the North Atlantic, Asian Monsoon-Westerlies, and South American Monsoon regions. Our analysis suggests that the onsets of YD in the North Atlantic (12,870 ± 30 B.P.) and the Asian Monsoon-Westerlies region are essentially synchronous within a few decades and lead the onset in Antarctica, implying a north-to-south climate signal propagation via both atmospheric (decadal-time scale) and oceanic (centennial-time scale) processes, similar to the Dansgaard-Oeschger events during the last glacial period. In contrast, the YD termination may have started first in Antarctica at ∼11,900 B.P., or perhaps even earlier in the western tropical Pacific, followed by the North Atlantic between ∼11,700 ± 40 and 11,610 ± 40 B.P. These observations suggest that the initial YD termination might have originated in the Southern Hemisphere and/or the tropical Pacific, indicating a Southern Hemisphere/tropics to North Atlantic-Asian Monsoon-Westerlies directionality of climatic recovery.

Keywords: Younger Dryas; climate dynamics; event phasing; structure; timing.

Fig. 1.

Comparison between Greenland NGRIP ice-core and Seso speleothem δ¹⁸O records. (A, C) Greenland NGRIP (25) and Seso speleothem δ¹⁸O records (this study), respectively. (B) Comparison between NGRIP (blue) and Seso (gray) δ¹⁸O records. The error bars show the typical age error of each YD record (color-coded). The two vertical red dashed lines depict the initial onset (the abrupt drop at ∼12,870 ± 30 B.P.) and initial termination (initiated at ∼11,700 ± 40 B.P.) of the YD based on correlation of distinct features at subcentennial precision. The gray bar shows the YD termination excursion from ∼11,700 to ∼11,610 B.P. Kyr BP, 1 × 10³ B.P.

Fig. 2.

Comparison of δ¹⁸O records from the North Atlantic, East AM, Indian Monsoon, and AW domains. (A, B) NGRIP δ¹⁸O on GICC05 chronology (25) and Seso δ¹⁸O record from the North Atlantic, respectively. (C–H) Kulishu, Hulu (38), Qingtian (39), Shennong, Yamen (40), and Dongge δ¹⁸O records from the East AM domain, respectively. (I) Mawmluh (yellow) and Cherrapunji (marron) δ¹⁸O records from the Indian Monsoon domain. (J) Timta δ¹⁸O record from the Indian Monsoon domain (41). (K) Tonnel’naya δ¹⁸O record from the AW domain. (L) NGRIP Ca²⁺ on the GICC05 chronology (1) (SI Appendix, Fig. S1). Speleothem records are from this study except for those indicated by references. Error bars depict the typical age error of each record. Two vertical red dashed lines depict the initial onset (12,870 ± 30 B.P.) and termination (11,700 ± 40 B.P.) of the YD based on Seso and NGRIP δ¹⁸O records. The vertical bars show durations of full-onset (beige) and termination (gray) excursions of the YD. Kyr BP, 1 × 10³ B.P.

Fig. 3.

Comparison of speleothem δ¹⁸O records from North Atlantic and tropical Pacific regions. (A, B) NGRIP δ¹⁸O on the GICC05 chronology (25) and Seso δ¹⁸O record from the North Atlantic region, respectively. (C–F) Palawan (48), Borneo (49), Sumatra (50), and Liang Luar (51) records from the western tropical Pacific and nearby regions. (G, H) are NC-B/ELC-B/NAR-C (53, 54) and Juxtlahuaca (52) records near the eastern tropical Pacific. (I) Jaraguá record from the South American Monsoon domain (this study). (J) Patate record from the South Indian Ocean (59). Error bars depict the typical age error of each record. Two vertical dashed red lines mark the initial onset (12,870 ± 30 B.P.) and initial termination (11,700 ± 40 B.P.) of the YD. The vertical purple line indicates the initial termination in two SH records, (I) and (J), at ∼11,900 B.P., consistent with the WAIS record (Fig. 4). The vertical dashed green line indicates the beginning of the YD termination excursion in the western tropical Pacific at ∼12,300 B.P. Kyr BP, 1 × 10³ B.P.

Fig. 4.

Interpolar phasing. (A) NGRIP δ¹⁸O on the GICC05 chronology (25). Orange dashed lines and green squares depict trends and breakpoints of the record. (B) Seso δ¹⁸O record (this study). (C) Antarctic WDC δ¹⁸O record on the WD2014 chronology (61). Blue lines and green squares depict trends and breakpoints of the record, respectively. (D) Mean global ocean temperature record (62). The gray lines indicate uncertainty. (E) East AM δ¹⁸O record (Shennong record; this study). (F) Indian Monsoon δ¹⁸O record (Cherrapunji record; this study). (G) Atmospheric CH₄ records from the WDC ice core (olive, ref. ; black, ref. 61). (H) Atmospheric CO₂ record from the WDC ice core (on WD2014 chronology) (84). Error bars depict the typical age error of each record, except for CH₄ records, which show the uncertainty of the ice–gas age difference (61). The blue and gray errors for the NGRIP δ¹⁸O record depict NGRIP age error (GICC05 chronology) and the error based on synchronization to the Seso chronology, respectively. Two vertical red dashed lines depict the initial onset (12,870 ± 30 B.P.) and initial termination (11,700 ± 40 B.P.) of the YD in the NGRIP and Seso records. Two vertical purple lines indicate two breakpoints in the WDC δ¹⁸O record at ∼11,900 and ∼12,770 B.P. Two vertical gray dashed lines indicate the abrupt jump in North Atlantic temperature at ∼11,610 B.P. and the peak of AM and CH₄ around ∼11,450 B.P. at the end of the YD. The solid orange line depicts the Pt-anomaly in the GISP2 ice core (73) at ∼12,820 B.P. on GICC05 chronology (1). Two horizontal dashed gray lines in (H) depict an ∼15-ppm increase (red arrows) of atmospheric CO₂ since the initial onset of the YD. Kyr BP, 1 × 10³ B.P.