From a tube filled with mud to an environmental reconstruction
Lakes are abundant on the Earth and their sediments provide unique continuous climatic and environmental archives extending far back in time (some records >1 million years). Lakes capture local and regional climatic, environmental, and anthropogenic signals that eventually are incorporated in their sediments. When the sedimentation process is undisturbed, the youngest material deposits on top overlying the older material and thus, the age of the sediments increases with depth.
Sedimentologists take advantage of this feature and drill sediment cores perpendicularly to the sediment-water interface at the depocenter (deepest point in the lake) to extract chronologically ordered records. The longer the sample core (the deeper in the sediment), the further back in time it goes. Back in the laboratory, the sediment cores are split lengthwise and an age-depth model is established on one half of the sediment core to convert the sediment depths into specific ages. The other half of the sediment core is subjected to a range of analytical measurements allowing for the reconstruction of multiple environmental and climatic indicators (e.g., mineralogy, algal remains, plant pollens, bacterial remains, DNA fragments, etc.).
The combination of the information obtained on both halves (the measured indicators with the age-depth model) finally results in a reconstruction of the past climatic and environmental conditions. These reconstructions can then be used to elucidate regional environmental and climatic changes and fluctuations of the past and thus, build the foundation to investigate the nexus of climate, environment, ecosystems, and humans.
Holocene climate variability from Kerguelen Islands and NE Greenland: combining sedimentary lipid biomarkers with hyperspectral imaging techniques
Currently (2021-2022), I am hosted by Prof. Dr. William J. D'Andrea and conduct my SNSF Postdoc.Mobility project. The project aims at providing hydroclimate and high-resolution temperature reconstructions from the Southern Ocean (Kerguelen islands) and from northeast Greenland (Pearyland). The research is based on the analysis of Holocene-length lake sedimentary records. We apply a combination of scanning techniques (X-Ray fluorescence scans, CT-scans, hyperspectral imaging), biogeochemical methods (lipid biomarkers such as branched Glycerol dialkyl glycerol tetraethers and H-isotopes measured on leaf waxes), and chronological techniques (radiocarbon dating) to reconstruct the regional temperature and hydroclimate of the past.
Information about the Greenland project can be found on wandeldal.org.
Past climate variability from SE and N Greenland lake sediments: exploring the potential of sedimentary lipid biomarkers combined with novel hyperspectral imaging techniques
I was awarded an SNSF early Postdoc.Mobility fellowship (2019-2021), which allowed me to conduct this project at the Climate System Research Center (CSRC) and the Biogeochemistry Laboratory (BGC Lab) at UMass, Amherst, MA, where I was hosted by Prof. Dr. Isla S. Castañeda, and Prof. Dr. Raymond S. Bradley. Based on lake sediments from Lake 578 in SW Greenland, in the vicinity of the fjord where Erik the Red arrived in the year 985 CE, we established a Holocene-length temperature, productivity and anoxia reconstruction combining brGDGTs (branched glycerol dialkyl glycerol tetraethers) and hyperspectral imaging. Although the Holocene-reconstruction paper is still in preparation, I contributed as a co-author to two recently published articles:
Zhao, B., Castañeda, I.S., Salacup, J.M., Thomas, E.K., Daniels, W.C., Schneider, T., de Wet, G.A., Bradley, R.S. (2022). Prolonged Drying Trend Coincident with the Demise of Norse Settlement, Southern Greenland. Science Advances. doi: https://doi.org/10.1126/sciadv.abm4346
Zhao, B., Castañeda, I.S., Bradley, R.S., Salacup, J.M., de Wet, G.A., Daniels, W.C., Schneider, T. (2021). Development of an in-situ branched glycerol dialkyl glycerol tetraether (brGDGT) calibration in Lake 578, southern Greenland. Organic Geochemistry. doi: https://doi.org/10.1016/j.orggeochem.2020.104168
Lake sediments as paleo climatic and environmental history archives - Case studies from Ecuador and Switzerland (Dissertation/ PhD Thesis)
In 2018, I obtained my PhD at the Oeschger Centre for Climate Change Research (OCCR), University of Bern, Switzerland supervised by Prof. Dr. Martin Grosjean. We investigated chronologically-well constrained lake sedimentary records of seven lakes at different altitudes located in the Cajas National Park, Ecuador, as well as a record from the Ponte Tresa basin of Lake Lugano, Switzerland. We applied a range of methods to reconstruct local eutrophication (green pigments, Lake Lugano), anthropogenic pollution (heavy metals, and polycyclic aromatic compounds, Ecuador), climate (ENSO, Lake Pallcacocha), and additionally established a tephrochronology for the studied lakes in Cajas Nationalpark.
Schneider, T., Bandowe, B.A.M., Bigalke, M., Mestrot, A., Hampel, H., Mosquera, P.V., Fraenkl, L., Wienhues, G., Vogel, H., Tylmann, W., Grosjean, M. (2021). 250-year records of mercury and trace element deposition in two lakes from Cajas National Park, SW Ecuadorian Andes. Environmental Science and Pollution Research. doi: https://doi.org/10.1007/s11356-020-11437-0
Arcusa, S. H., Schneider, T., Mosquera, P.V., Vogel, H., Kaufman, D., Szidat, S., Grosjean, M. (2020). Late Holocene tephrostratigraphy from Cajas National Park, southern Ecuador. Andean Geology 47(3), doi: http://dx.doi.org/10.5027/andgeoV47n3-3301
Schneider, T., Hampel, H., Mosquera, P.V., Tylmann, T., Grosjean, M. (2018). Paleo-ENSO revisited: Ecuadorian Lake Pallcacocha does not reveal a conclusive El Niño signal. Global and Planetary Change 168, p. 54-66, doi: https://doi.org/10.1016/j.gloplacha.2018.06.004
Schneider, T., Rimer, D., Butz, C., Grosjean, M. (2018). A high-resolution pigment and productivity record from the varved Ponte Tresa basin (Lake Lugano, Switzerland) since 1919: insight from an approach that combines hyperspectral imaging and high-performance liquid chromatography. Journal of Paleolimnology 60, p. 381-398, doi: https://doi.org/10.1007/s10933-018-0028-x
Bandowe, B. A. M., Fränkl, L., Grosjean, M., Tylmann, W., Mosquera, P. V., Hampel, H., Schneider, T. (2018). A 150-year record of polycyclic aromatic compound (PAC) deposition from high Andean Cajas National Park, southern Ecuador. Science of the Total Environment 621, p. 1652-1663, doi: https://doi.org/10.1016/j.scitotenv.2017.10.060
Climatic and environmental history of the past 1300 years based on multi-proxy sediment analyses from Laguna Escondida (38°S), Chilean Andes (Msc Thesis)
De Jong, R., Schneider, T., Hernández-Almeida, I., Grosjean, M. (2016). Recent temperature trends in the South Central Andes reconstructed from sedimentary chrysophyte stomatocysts in Laguna Escondida (1742 m a.s.l., 38°28 S, Chile). Global and Planetary Change 137, p. 24-34, doi: https://doi.org/10.1016/j.gloplacha.2015.12.006