Using stalagmite geochemistry to reconstruct paleoclimate in the Philippines during Heinrich Events

The Indo-Pacific Warm Pool (IPWP), a region in the western Pacific Ocean known as the “heat engine of the globe”, is critical for modulating global climate patterns. Tropical island nations within the IPWP are especially well suited to study how the IPWP will respond to anthropogenic climate change. To understand the effects of future climate change within the IPWP, it is useful to look to past rapid climate change events, like Heinrich Events, which were periods of Northern Hemisphere freshwater forcing. Despite the critical role that paleoclimatic studies of Heinrich Events play in constraining the effects of future climate change, there are few terrestrial paleoclimate records from within the IPWP focusing on these events. Here, we use speleothems from the Puerto Princesa Underground River cave (PPUR) in Palawan, Philippines to reconstruct rainfall patterns during Heinrich Events. We present a combined record of δ18O, δ13C and trace elements (Mg/Ca, Sr/Ca, and Ba/Ca) for two stalagmites (GP-0 and GP-1) from PPUR’s Gaia Passage. GP-0 is 10.5 cm in length and grew between 41,855 ± 1099 to 31,637 ± 280 years B.P. (±2𝜎). GP-1 is 12.5 cm in length and grew between 40,849 ± 272 to 20,914 ± 206 years B.P. (±2𝜎). Taken together, our partially replicated record spans 41.9 to 20.9 ka and provides a robust dataset highlighting the effects of Heinrich Events 2, 3, and 4 on the southwestern Philippines and IPWP. Preliminary δ18O results show approximately 1.5 ‰ variability, suggesting fluctuations between wetter and drier intervals through time. In addition, statistically significant co-variation between Mg/Ca, δ18O, and δ13C indicates that prior calcite precipitation influences the GP-0 and GP-1 records. Additional statistical analyses between the geochemical results of GP-0 and GP-1 during coeval periods of growth will provide a strong understanding of the mechanisms driving rainfall in the Philippines during periods of rapid climate change. Regional comparisons to other archives (speleothems, marine core records) will help to elucidate the ocean-atmosphere feedbacks driving rainfall variability within the IPWP. A comparison to iTRACE climate model output across Heinrich Event 1 will broaden our understanding of the regional hydroclimate response to high latitude forcing. Furthermore, these results will inform much needed policy for water resource management and effective climate adaptation and resilience in the tropics.