Decoupling Local and Global Influences on South American Monsoon Dynamics During MIS 8/9: Insights from Peruvian Andes Stalagmites

The strength of the South American Monsoon (SASM) is captured in paleoclimate stalagmite records from the Peruvian Andes near Junín. Comparisons between these stalagmite records and global climate data reveal consistent trends. However, global records often fail to capture local or environmental variability, which is critical for understanding regional climate dynamics. This study analyzes data from three stalagmites from Huagapo Cave (located at -8.533°N, 120.433°E), which provide insights into local climatic influences. The stalagmites offer a high-resolution record of Marine Isotope Stages (MIS) 8 (244-301 ka) and 9 (301-334 ka), including trace metal ratios (Ba/Ca, Sr/Ca) and stable isotopes (δ18O, δ13C ). While δ18O generally aligns with summer insolation patterns, a notable deviation occurs during MIS 8 (~260-280 ka), where δ18O diverges from insolation trends. This anomaly is hypothesized to reflect northern hemisphere influences, potentially linked to glacial conditions that introduced freshwater into the oceans, disrupting Atlantic Meridional Overturning Circulation and weakening the SASM. Trace metal ratios and δ18O exhibit statistically significant correlations (P ≈ 0.02, calculated using Pearson's product-moment correlation in R), though δ18O is influenced by global factors, whereas trace metals reflect localized precipitation. Future work will focus on δ13C and trace metal data to further elucidate local environmental conditions in the Junín region of the Peruvian Andes.