ORCID
https://orcid.org/0000-0001-7997-4016
Date of Award
12-12-2023
Degree Name
Doctor of Philosophy (PhD)
Degree Type
Dissertation
Abstract
The tropical and central Andean highlands (>4,000 m above sea level) supply critical freshwater resources to the Amazon Basin, supporting large communities in mountain regions and lowlands. Due to the scarcity of historical weather data spatially and temporally, it is challenging to quantify hydroclimate and environmental responses to anthropogenic climate change. Paleoclimate reconstruction and modeling can provide critical insights into key hydroclimate processes and how hydroclimate in this region has responded to climate change and variability through time. However, biomarker-based paleoclimate proxy reconstructions are still very rare in this region. This dissertation quantifies local-scale and regional-scale hydroclimate and environmental changes in the tropical and central Andes over the past 2,700 years using geochemical proxies from lake sediments, peats, and soils, and computational approaches. I first develop past air temperature records based on glycerol dialkyl glycerol tetraethers (GDGTs), a group of archaeal and bacterial lipid membranes, preserved in lake sediments, peats, and soils, and compare them to climate indices to evaluate how this region’s air temperature has responded to climate forcings and natural climate variability in inter-decadal to millennial timescales. I apply instrumental data, climate reanalysis, and climate model outputs to a calibrated 1-D lake energy balance modeling to assess higher frequency variability (sub-daily to sub-decadal) in recent air and lake temperatures as well as to predict future changes. Finally, I present records of leaf wax n-alkane stable isotopes preserved in lake sediments and peat samples from the Sibinacocha Watershed in the Cordillera Vilcanota, Peru. I find that these records track the South American Summer Monsoon variability similarly to isotope-based hydroclimate reconstructions from different sites across the Peruvian Andes. Coupled with lake sediment geochemistry, they can also offer critical information on local hydroclimate and landscape productivity changes in the Cordillera Vilcanota. This dissertation offers the first quantitative GDGT-based temperature reconstruction from the central Andean highlands. Together with leaf wax isotope records and lake energy balance modeling, the results allow me to identify potential climatic drivers controlling high-alpine hydroclimate, glacial activity, and lake thermal properties in this region under natural and anthropogenic climate changes and variability. These findings are critical for future studies on climate sensitivity and high-alpine environmental responses to current and future climate changes.
Language
English (en)
Chair and Committee
Bronwen Konecky
Recommended Citation
Sae-Lim, Jarunetr, "Paleoclimate of the Peruvian Andean highlands during the late Holocene" (2023). Arts & Sciences Electronic Theses and Dissertations. 3199.
https://openscholarship.wustl.edu/art_sci_etds/3199