Precession-induced millennial climate cycles in greenhouse Cretaceous

Area of Science:

• Paleoclimatology
• Climate Dynamics
• Geological Sciences

Background:

• Millennial-scale climate cycles are observed in greenhouse climates, but their underlying mechanisms are not well understood.
• Previous research has not clearly linked these cycles to specific astronomical forcings.

Purpose of the Study:

• To investigate the mechanisms driving millennial-scale climate cycles during the early Campanian greenhouse period.
• To determine the influence of astronomical parameters, specifically precession and eccentricity, on these climate cycles.

Main Methods:

• Utilized centennial-resolution geological proxy reconstructions from East Asia and the Southern Atlantic.
• Analyzed amplitude modulation relationships between climate cycles and orbital parameters (precession and eccentricity).
• Compared proxy data with theoretical calculations of equatorial insolation cycles.

Main Results:

• Documented pronounced millennial (1-6 kyr) wet-dry climate cycles in early Campanian greenhouse deposits.
• Established a direct correlation between ~4-5 kyr climate cycles and predicted equatorial insolation cycles.
• Demonstrated that precession directly and indirectly stimulates millennial climate cycles through nonlinear amplitude modulation.

Conclusions:

• Astronomical parameters, particularly precession, are key drivers of millennial climate cycles in greenhouse conditions.
• The identified deterministic link suggests potential predictability of high-frequency climate oscillations in future warming scenarios.
• Findings provide crucial insights into climate dynamics under sustained warm, greenhouse-like conditions.