A global Bayesian temperature calibration for lacustrine brGDGTs

Despite widespread use of branched glycerol dialkyl glycerol tetraethers (brGDGTs) for paleo-temperature reconstruction, no global calibration for their application in lakes has been generated since improved analytical methods have allowed for the separation of the structural isomers [Hopmans et al., 2016]. This is a substantial obstacle for the application of this tool as soil calibrations underestimate temperature values when applied to lake sediments. In order to generate a global calibration, we present a comprehensive dataset (N = 272) of lacustrine brGDGT distributions, consisting of both new and previously reported samples [Boldt et al., 2015; Dang et al., 2018; 2016; Li et al., 2017; Stefanescu et al., 2021], spanning a wide range of geographical locations. In addition, we compiled environmental information from these locations through in situ measurements [Li et al., 2017] and literature search for pH, conductivity, and nutrient content. For parameters such as mean annual air temperature (MAAT), temperature of months above freezing (MAF), mean annual precipitation (MAP), we estimated values from either the CRU [Osborn and Jones, 2014] or PRISM [https://prism.oregonstate.edu/] products depending on the location. Our new calibration [Martínez-Sosa et al., 2021] facilitates the use of lacustrine brGDGTs to reconstruct continental temperatures, a vital piece of information for understanding past climates.