NOAA/WDS Paleoclimatology - Huagapo Cave, Peru 7,200 Year Speleothem Stable Isotope Data

Stable oxygen isotope (d18O) measurements of two speleothems, collected from Huagapo Cave in the central Peruvian Andes and with overlapping age from 1.1 to 1.4 ka, characterize tropical South American climate variability over the last 7150 years. In the study region, precipitation d18O (d18Op) is inversely correlated to rainfall amount upstream in the Amazon Basin and the intensity of convection associated with the South American summer monsoon (SASM). Speleothem long-axis profiles yield an average age resolution of five years and permit investigation of climate over orbital to decadal timescales. Variations in the isotopic composition of Huagapo Cave calcite (d18Oc) are in good agreement with several precipitation proxy records from ice cores, speleothems, and lake sediments from the central Peruvian Andes. From the mid-Holocene to today, d18Oc, a proxy for d18Op, tracks changes in local insolation and exhibits a ~2 per mil decrease. In the Late Holocene, Huagapo Cave d18Oc is characterized by two periods of significant decline in SASM intensity (up to 1.5 per mil increase in d18Oc) even when insolation is reaching a local maximum and the SASM would be expected to intensify. These millennial-scale reductions in SASM intensity could in part be influenced by a reduction in the zonal SST gradient of the Pacific Ocean, favoring El Nino-like development.