ORGANIC BIOMARKER BASED CLIMATE RECONSTRUCTION IN SOUTHERN GREENLAND AND ITS RELATIONSHIP TO THE DEMISE OF NORSE SETTLEMENTS

• Main Author: Zhao, Boyang
• Format: Text
• Language: unknown
• Published: ScholarWorks@UMass Amherst 2021
• Subjects: Paleoclimate; Organic biogeochemistry; Climate–human–environment interactions; Branched GDGT; Leaf wax hydrogen isotopes; Greenland; Biogeochemistry; Climate; Sedimentology
• Online Access: https://scholarworks.umass.edu/dissertations_2/2391; https://doi.org/10.7275/24528222; https://scholarworks.umass.edu/context/dissertations_2/article/3428/viewcontent/dissertation_Boyang_Zhao_v2.3.pdf

Climate change is an urgent, complicated, and challenging issue for human society today. Changing climate may have large and unexpected influences on the global environment, leading to severer living conditions for billions of people on our planet. To better elucidate relationships between climate change and human societies, we can look back and try to disentangle climate–human–environment interactions in the past. Because the period of instrumental measurements is quite short, it is important to reconstruct past climate using different proxies in geologic materials (Bradley, 2014). Among different proxies in a variety of natural archives, organic biomarkers preserved in lake sediments stand out for providing continuous, high-resolution, and comprehensive climate information from massive locations across the globe (Castañeda and Schouten, 2011). Organic molecular biomarkers in lake sediments are the individual compounds that can be used to trace to the particular source organism, bioprocess, and the environmental conditions at the time of deposition (Castañeda and Schouten, 2011). Among a wealth of biomarkers, branched glycerol dialkyl glycerol tetraethers (brGDGTs) and leaf wax (n-alkanes) are considered to be useful tools, and have been widely applied to lake sediments to generate temperature and hydroclimate reconstructions (e.g., Thomas et al., 2018). BrGDGTs are bacterial membrane lipids, containing tetra- (I), penta- (II), or hexamethylated (III) components, with zero (a), one (b), or two (c) cyclopentyl moieties (Sinninghe Damsté et al., 2000; Weijers et al., 2006; De Jonge et al., 2013). These compounds are ubiquitous in peats, soils, lacustrine and marine sediments (Schouten et al., 2013). Although the brGDGTs source organisms are still largely unknown (Sinninghe Damsté et al., 2018; van Bree et al., 2020), the methylation index of brGDGTs (MBT′5ME) of surface soils and peat is significantly correlated with mean annual air temperature (MAAT) on a global scale (Weijers et al., 2007; De Jonge et ...