Biomarker Reconstruction of Tropical High-Elevation Climate in the Rwenzori Mountains

High-elevation tropical regions are believed to be some of the most sensitive environments to climate change. In tropical African mountains, the effects of climate warming have already caused glaciers to significantly retreat in the past century, and recent droughts, fires, and floods suggest that climate warming is impacting a variety of ecosystem processes and services. However, the short duration of observational records limits our ability to test whether these changes result from shifts in precipitation, temperature, or human activities. The Rwenzori Mountains, located on the border between Uganda and the Democratic Republic of the Congo, is one such region where the impacts of warming are apparent. To assess the driving mechanisms of these modern climatic and environmental changes, we use branched glycerol dialkyl glycerol tetraethers (brGDGTs), hydrogen and carbon isotopes of leaf waxes (δDwax and δ13Cwax), and polycyclic aromatic hydrocarbons (PAHs) from lake sediments to reconstruct climate during the Holocene in the Rwenzori Mountains. Here, we present the highest elevation records of climate in Africa using sediment cores from two different lakes: Lake Africa (3895 m asl) and Lake Kopello (4017 m asl). We find that despite evidence for amplification of climate changes at high altitudes, we observe similar amplitudes and trends in δDwax consistent with other regional records. Additionally, we find that although there are changes in hydroclimate and fire regimes across the Holocene at these sites, there is no clear shift in vegetation as recorded by δ13Cwax. Our records, combined with others in the Rwenzori Mountains and elsewhere in East Africa, demonstrate regional similarity in climate across sites despite elevational differences. These records serve to improve our understanding of Afroalpine climate-ecosystem dynamics and evaluate how high-elevation tropical regions may respond to anthropogenic warming.