Orbital eccentricity and internal feedbacks drove the Triassic megamonsoon variability.

Area of Science:

• Paleoclimatology
• Earth System Science
• Orbital Dynamics

Background:

• The Triassic megamonsoon's evolution is linked to Earth's orbital variations.
• The precise mechanisms driving these orbital-scale monsoon cycles remain unclear.

Purpose of the Study:

• To investigate orbital-scale megamonsoon variability during the Middle Triassic (246–239 Ma).
• To synthesize paleoclimate data with climate models to understand monsoon dynamics.

Main Methods:

• Integrated high-resolution reconstructions of hydrologic fluctuations from lacustrine sediments (Ordos Basin).
• Utilized lithological and magnetic susceptibility data series.
• Employed climate simulations and data-model synthesis.

Main Results:

• Identified monsoon cycles in the 20, 100, and 405 kyr Milankovitch bands.
• Revealed a ~3.3 Myr eccentricity-related cycle influencing monsoons, temperature, carbon cycles, and sea level.
• Earth system models demonstrated the impact of orbital configurations and CO₂ on megamonsoon dynamics.

Conclusions:

• Orbital forcing and Earth system feedbacks significantly shape long-term megamonsoon variability.
• Megamonsoon dynamics exhibit threshold responses to solar radiation.
• Findings enhance understanding of astronomical influences on paleoclimate patterns.