Interhemispheric monsoon dynamics over the past 450,000 years.

Monsoon variability over the past 450,000 years is linked to Milankovitch forcing and internal boundary conditions, with notable out-of-phase behavior between hemispheres.

• Why it matters: Understanding monsoon changes over glacial-interglacial cycles is crucial for predicting future climate impacts, yet records from the Southern Hemisphere are limited, hindering comprehensive insights.
• What they did: The study analyzed speleothem oxygen-isotope data from the Amazon Basin to reconstruct South American Summer Monsoon variability and compared it with Asian monsoon records, identifying ten synchronous events.
• The result: Findings suggest that greenhouse gases, thermal gradients, and sea surface temperatures influence monsoon reorganizations, especially during periods of rapid planetary boundary condition changes.