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.
Northernmost Holocene temperature record inferred from lake sediments: quantitative lipid biomarker thermometry from 83.5° N Greenland (in progress), SNSF-project page
During this SNSF Postdoc return phase project (P5R5PN_214300), I am hosted by Prof. Dr. Nathalie Dubois at the Swiss Federal Institute of Aquatic Science and Technology (EAWAG, ETH Domain) Dübendorf.
Heatwaves and cold weather extremes observed in the midlatitudes have become more frequent in recent decades manifested for instance by the European record heat extremes of summer 2022. One of the reasons for these prolonged and more frequent extreme weather patterns is the reduction of the poleward temperature gradient. To better assess the impacts of current anthropogenic warming on this gradient, we need to investigate previous warm phases. However, meteorological records are too short to capture warm phases during the Holocene. Therefore, we investigate in this project the potential of lake sediments from Lake 1, one of the northernmost lakes on the Earth as temperature archive to fill the gap of temperature records. We will employ a combination of brGDGT-thermometry and alkenone-thermometry to reconstruct the temperature variability of the Holocene on Pearyland. Specifically, two main research questions will be addressed: 1) How does the rate of temperature change reconstructed from previous warm phases compare to the rate observed during the anthropogenically forced current warming period? 2) Was there a different latitudinal temperature gradient present during previous warm phases than observed in the current warming period? Aside from new quantitative temperature reconstructions from the northernmost landmass on Earth, the systematic comparison of two increasingly applied paleothermometers will contribute to the molecular paleoclimatology field.
Holocene climate variability from Kerguelen Islands and NE Greenland: combining sedimentary lipid biomarkers with hyperspectral imaging techniques (2021-2022), SNSF-project page
I was hosted by Prof. Dr. William J. D'Andrea to conduct my SNSF Postdoc.Mobility project at the Lamont-Doherty Earth Observatory, Columbia University NY.
Meteorological measurements reveal that the polar regions, which contain the largest ice bodies and host dominant climate modes, warm at an increased rate compared to the global mean. To further investigate the effects of the recent warming, it is vital to disentangle the human-induced changes from the natural climate variability and to place these observations in a long-term context. However, meteorological records in these data-limited areas are too short to capture long-term trends. Thus, an alternative approach is to examine climate reconstructions based on climate proxies - indirect indicators of climate change - extracted from natural climate archives, such as lake sediments. This project focused on contributing new hydroclimate and temperature reconstructions based on lake sedimentary records from data-limited regions in the sub-Antarctic (Kerguelen Islands) and the high Arctic (Pearyland, N Greenland) in order to fill this data gap. We specifically aimed at 1) reconstructing the Holocene-length climate variability from Lake 5 (49.1°S, 69.1°E) on the Kerguelen Islands; 2) providing a multiproxy reconstruction from Lake SW, N Greenland (82.1°N; 35.7°W); and 3) comparing the reconstructions obtained from each hemisphere with each other. We applied a workflow combining a suite of lipid biomarkers, used as temperature- (alkenone-thermometry) and hydroclimate- (δ2H measured on leaf waxes; n-alkanes and fatty acid methyl esters, FAMEs) proxies, with hyperspectral imaging inferred proxies for productivity (green pigments) and anoxia (bacterio-pheophytins) along with a range of other sedimentologic proxies (C/N-analyses, µXRF-scans, CT-scans, and age-depth modeling). The publications are in preparation.
More 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 (2019-2021), SNSF-project page
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. While the Holocene-length reconstruction paper is still in preparation, two articles were recently published:
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), SNSF-project page
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