Collaborative Research: Quantitative Reconstructions of Last Millennium Hydroclimate and Temperature from the Tropical High Andes

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This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).Glaciated mountain ranges in the Earth’s tropical regions provide critical freshwater resources to local and downstream communities and support richly diverse ecosystems. Yet warming at high elevations (12,000’) is expected to amplify in the future, with the disappearance of many glaciers projected by the mid-21st century. The Cordillera Vilcanota (Peru) is the second largest glacierized mountain range in the Andes, is home to world’s second-largest tropical ice cap, Quelccaya and is a principal source of the Amazon River. However, because instrumental records are sparse, variations in temperature and precipitation prior to the late 20th century are poorly constrained. This project will reconstruct patterns of temperature and moisture availability over the past several centuries using two closely-situated but distinct climate archives: lake/peat sediments and ice cores. Lake and peat sediments accumulate over time, preserving biological and chemical indicators of past temperature and precipitation. Project deliverables include climate reconstructions from well-instrumented Andean lakes and peats, which will imporve the utility of biomarker-based temperature proxies, and enhanced leaf wax and ice cory proxy system models. This project will also support efforts to broaden participation from underrepresented groups in STEM and to develop K-12 educational resources, including development of climate change education modules for high schools, and providing hands-on workshops, training and experiential learning opportunities.Researchers will analyze sediments from sites in and around Lake Sibinacocha (16,043’) and use lake and ice models, calibrated using existing instrumental measurements, to compare these reconstructions to Quelccaya Ice Cap (QIC) ice cores. Results will provide validation and information on air temperature, lake temperature, and moisture changes as the high Andes transitioned from a cold period (the Little Ice Age) to the industrial period. Climate model simulations of the past 1,000 years will contextualize the extent to which these changes were driven by remote processes such as the South American Summer Monsoon and sea surface temperature variations in the tropical Pacific, putting current Andean climate change into a long-term historical context. Data will be generated to reconstruct precipitation δD (δDprecip) from leaf waxes, temperature from glycerol dialkyl glycerol tetraethers (GDGTs), and runoff and precipitation/evaporation from lithologic, bulk geochemical, and paleoecological sensors. Temperature reconstructions will be compared from glacial and non-glacial lakes and peatlands, and air/lake temperature relationships will be quantified using an energy balance model. Proxy system models (PSM) will be used to evaluate the sensitivity of δ18Oprecip, δDprecip, and δDwetland reconstructions from ice cores and sediments to seasonal and mean annual climate variables. Forced responses vs. internal variability will be investigated with isotope-enabled Last Millennium simulations. Because δ18Oice and δDwax both track the stable isotopic composition of precipitation but with differing sensitivities to humidity, evaporation, and seasons of deposition/ablation, the project’s dual-PSM approach will allow multiproxy reconstructions of δ18Oprecip, δDprecip, and temperature while providing new constraints on local evaporative conditions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.