Precession-induced millennial climate cycles in greenhouse Cretaceous

Abstract

Millennial-scale climate cycles persist throughout greenhouse climates, yet the mechanisms remain unclear. Here, using proxy reconstructions, we present centennial-resolution geological records from early Campanian greenhouse deposits in both mid-latitude East Asia and low-latitude Southern Atlantic. These records document pronounced millennial ( ~ 1-6 kyr) wet-dry climate cycles. The amplitude modulation relationship between the most prominent ~4-5-kyr cycles (corresponding to the ¼ precession cycle) and eccentricity aligns perfectly with the theoretically calculated equatorial insolation cycles, demonstrating the climate effect of this predicted insolation forcing on global climate. Other millennial cycles primarily emerge from these ~4-5-kyr cycles via nonlinear amplitude modulation and combination tones. Proxy reconstructions and theoretical calculation thus converge to demonstrate that during this warm greenhouse period, precession can directly and indirectly stimulate millennial climate cycles. The deterministic link between astronomical parameters and millennial climate cycles implies that high-frequency climate oscillations may be predictable in future greenhouse-like climates, particularly under anthropogenic warming.

Fig. 1. Spatial and temporal distribution of sedimentary records displaying millennial-scale climate cycles throughout the Mesozoic and Paleozoic Eras.

A Modern geographic location of records which preserved millennial-scale climate cycles throughout the Mesozoic and Paleozoic Eras, and of study sites related in this study. The detailed information of these records, including paleogeographic locations and chronologies, are compiled in Table S1. The world map was generated using the geom_map function in the R package ggplot2. B The latitudinal extent of continental ice sheets, excluding Alpine glaciers. C The temporal distribution of millennial-scale climate cycles reported throughout the Mesozoic and Paleozoic Eras.

Fig. 2. Quarter-precessional cycles in Cretaceous terrestrial and marine records.

A–C Grayscale, log (Ca/Ti), and Rb/Sr datasets from the SK2 borehole with their ~95.2-kyr (0.0105 ± 0.0035 cycle/kyr), ~22-kyr (0.0455 ± 0.0095 cycle/kyr), and ~4–5-kyr (0.215 ± 0.055 cycle/kyr) filters. D The astronomically-tuned L* datasets (blue) based on TimeOpt chronology (Fig. S4) and anchoring to the magnetostratigraphic age at 1145.132 m (80.702 Ma), with precessional filters (0.054 ± 0.011 cycles/kyr). E The evolutive power spectra of L* using the EHA method, with ~405-kyr filter of tuned L*. F The selected intervals of tuned L* showing quadripartite structure, in which every precession cycle (0.054 ± 0.011 cycles/kyr) includes two semi-precessional (0.1 ± 0.02 cycle/kyr) and four quarter-precessional (0.215 ± 0.055 cycle/kyr) cycles. The quarter-precessional cycles in L* are most prominent at peaks of the 405-kyr filter of L*, indicating an intermodulation relationship between quarter-precessional cycles and long eccentricity.

Fig. 3. Bicoherence spectra based on the WOSA method (the contour plots).

A Periodogram power spectra (upper panel) and p-values for the null hypothesis (middle panel), as well as the bicoherence spectra (bottom panel) of grayscale datasets from the SK2 borehole. B, C Same as (A) but for log (Ca/Ti) from the SK2 borehole and L* datasets from the DSDP–16 F borehole. The bicoherence spectral analysis uses four segments with 50% overlap and a Hanning taper. Thick black contours highlight bicoherence results exceeding the 95% confidence level. Because the FDR-corrected p-values for the power peaks at ~1.8–2.5 kyr in Rb/Sr are larger than 0.2, the Rb/Sr bicoherence plot is shown in Fig. S5 instead.

Fig. 4. Quarter-precessional cycles in theoretical insolation curves and their comparison with geological proxy reconstruction.

A The theoretically-proposed largest equatorial seasonal insolation amplitude (termed equatorial insolation). The insolation amplitude is estimated from the differences between the two insolation maxima at spring and fall equinoxes and the two insolation minima at summer and winter solstices, that is, max (SE, FE)-min (SS, WS), where SE, FE, SS, WS denote the spring equinox, fall equinox, summer solstice, winter solstice, respectively. B The combined effect of equatorial and bi-hemisphere maximum insolation. C The log (Ca/Ti) in the SK2 of SLB. D The periodogram spectra of equatorial insolation. E The periodogram spectra of the combined effect of equatorial and bi-hemisphere maximum insolation at 8 °N/S.