Using Peruvian Speleothems to Depict Natural Climate Variation

Studying the paleoclimate of our planet is vitally important to predict future patterns as the current climate changes. Global CO₂ levels are reaching 419 ppm and continue to climb due to anthropogenic processes, such as burning fossil fuels. By studying proxy records like stalagmites, we can understand the deviation of the current climate from the natural system. This study examines two stalagmites found in Huagapo Cave, Peru and looks at the natural climate change signal from these records by analyzing their stable carbon and oxygen isotopes. Huagapo Cave is in the Peruvian Andes in Palcamayo, Peru at 11.27°S; 75.79°W. The cave is 3,850 meters above sea level and near 2,800 meters in length. Stalagmite 19-3 is dated by using U/Th ages and is from Marine Isotope Stage (MIS) 11 with the ages 375,799 ka (± 4225) – 375,177 ka (± 4303). The third U/Th date does not fit this age model and with the current ages having errors of over 4,000 ka, another method is needed to date this stal. Because the original ages place this stal at the MIS 10/11 boundary, comparing 19-3 to other records from interglacial and glacial periods suggest 19-3 is from MIS 10 given the strong correlation of glacial d¹⁸O values between -14.5‰ to -18.5‰ when comparing stals. The results of 19-3 show the d¹⁸O and d¹³C values being plotted with MIS 10 insolation, which is the sun’s incoming solar energy, and there is a high-resolution match when comparing these two records. Stalagmite 19-5b is also dated from U/Th ages, placing it in MIS 6 and spanning 169,908 ka (± 694) – 156,041 ka (± 491). 19-5b is the stub to 19-5a in Huagapo Cave and these two records were compared. The results of this study show d¹⁸O and d¹³C values from 19-5b replicating the isotope values from 19-5a. 19-5b is also plotted with insolation from MIS 6 and both isotopes (d¹⁸O and d¹³C) match MIS 6 insolation at a high resolution. The results from both stalagmites (19-3 and 19-5b) show the d¹⁸O and d¹³C values mirroring each other and both indicate that the signal of insolation is a dominant control in the Peruvian climate system. This research matches findings in previous studies which suggest that the fluctuation of insolation drives the seasonality of SASM (South American Seasonal Monsoon) and the movement of the ITCZ (International Tropical Convergence Zone) which dictates the hydroclimate of Peru.