South American precipitation dipole forced by interhemispheric temperature gradient

Area of Science:

• Paleoclimatology
• Climate Dynamics
• South American Hydroclimate

Background:

• Tropical South America's hydroclimate supports high biodiversity and large populations.
• Amazonia and northeastern Brazil are vulnerable climate change hotspots with uncertain future hydroclimate.
• A proposed precession-driven precipitation dipole between western Amazonia and northeastern Brazil lacks robust long-term evidence.

Purpose of the Study:

• To investigate the persistence of the precession-driven South American precipitation dipole over the last 113,000 years.
• To reconstruct past precipitation patterns in northeastern Brazil to test the dipole hypothesis.
• To understand the mechanisms driving hydroclimate variability in tropical South America.

Main Methods:

• Analysis of quartz thermoluminescence sensitivity in marine sediment cores from northern northeastern Brazil.
• Reconstruction of a 113,000-year precipitation record for northeastern Brazil.
• Modeling the influence of precession-induced insolation changes on regional climate dynamics.

Main Results:

• The study confirms the existence and persistence of the precession-driven South American precipitation dipole over the last 113,000 years.
• A detailed precipitation record from northeastern Brazil supports the anti-phased relationship with western Amazonia.
• Precession-induced insolation changes were identified as the primary driver, modulating the Walker circulation and ITCZ migration.

Conclusions:

• The long-term South American precipitation dipole is a robust feature of the region's hydroclimate.
• Understanding these paleoclimatic dynamics is essential for predicting future hydroclimate shifts under global warming.
• Changes in the interhemispheric temperature gradient, influenced by modern warming, may alter this established precipitation pattern.