Investigation of climate, terrestrial ecosystems, and aquatic productivity during the past 1,500 years from the Lake Sibinacocha watershed, Peruvian Andes

Climate change is projected to drive glacial retreat and changes in freshwater availability, but historical hydroclimate data from high elevations in the Andes of South America are spatially inconsistent and most temperature observations are either short or nonexistent. Here we present a record from the central high Andes in order to understand long-term interactions among alpine ecosystems, climate changes, and human influences during the past ~1,500 years. We present initial biomarker data from sediment cores collected from the watershed of Lake Sibinacocha (13.86 S, 71.02 W; 4860 m a.s.l.), ~20 km northwest of the Quelccaya Ice Cap. We analyzed long-chain n-alkanes and n-alkanoic acids (leaf waxes) to reconstruct terrestrial vegetation community and precipitation, branched glycerol dialkyl glycerol tetraethers (brGDGTs) to reconstruct temperature, and bulk and isotope carbon and nitrogen to reconstruct past aquatic productivity. Preliminary results based on the MBT'5Me calibration, which yields brGDGT temperatures similar to present-day lake temperatures, reveal that the Sibinacocha watershed warmed by ~2°C in the last ~200 years. The average chain length of long-chain n-alkanes suggests a stable regional vegetation community, with possible long-range transport of waxes from lowland ecosystems. We contextualize our paleoclimatic data with the aid of regional paleoclimate reconstructions and the archaeological record in order to better understand long-term relationships between the high Peruvian Andean environment and climate change due to both natural forcing and humans. This will provide a foundation for future paleo-ecological research and water resource management in the central Andes.