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Validation and application of a novel, terrestrial biomarker-based paleo thermometer to Holocene Swiss lake sediments and soils

English title Validation and application of a novel, terrestrial biomarker-based paleo thermometer to Holocene Swiss lake sediments and soils
Applicant Niemann Helge
Number 140662
Funding scheme Project funding (Div. I-III)
Research institution Institut für Umweltgeowissenschaften Universität Basel
Institution of higher education University of Basel - BS
Main discipline Other disciplines of Environmental Sciences
Start/End 01.10.2012 - 30.09.2015
Approved amount 210'109.00
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All Disciplines (5)

Discipline
Other disciplines of Environmental Sciences
Organic Chemistry
Climatology. Atmospherical Chemistry, Aeronomy
Hydrology, Limnology, Glaciology
Pedology

Keywords (9)

Switzerland; MBT/CBT-paleothermometer; Lipid Biomarker; Paleotemperature; branched GDGT; Proxy indicator; Sediments; Paleoclimate; Lakes

Lay Summary (English)

Lead
Lay summary
Of paramount importance for our comprehension and simulation of recent and future climate change is the precognition of climate variations in Earth’s history, yet instrumental and reliable historical data are only available for the last few centuries. For times scales beyond this very recent past, climate variations can be reconstructed with the aid of proxy-indicators in climate archives such as ice sheets, spelotherms, as well as aquatic sediments. Albeit the importance of the terrestrial realm in the global climate, paleoclimatological research traditionally focused on marine sediments. Typically, these span very long time periods, but they are rarely suitable to resolve sub-millennial time scales. Where they exist, the continental temperature (T) reconstructions are often limited to relative T fluctuations. A promising approach to go beyond the qualitative assessment of T variability in the past is to use a temperature-proxy, which is based on the analysis of (presumably) soil-bacterial lipids preserved in sedimentary archives, and which allows for absolute T reconstructions. This paleothermometer relies on the relative abundance of methyl-branched and cyclic dialkyl glycerol tetraethers (GDGTs) (i.e., MBT/CBT-indices), which changes in response to mean annual air temperature (MAAT) (Weijers et al. 2007a). In addition to information on MAAT, MBT/CBT-measurements allow for the reliable assessment of soil-pH, which can be a qualitative indicator of climate wetness. 
Similar to marine sediments, lake sediments are important geological archives, which may span time intervals from thousand to hundred thousands of years, and, hence, have a high potential for portraying long-term terrestrial climate variations. While MBT/CBT-ratios were successfully used to reconstruct mean annual air temperature (MAAT) from soils, the applicability of this paleothermometer to lacustrine sediments needs substantial testing. To date, for example, most of the existing MBT/CBT-measurements from modern lake sediments seem to consistently underestimate observational T-data, yet the mechanisms behind the observed discrepancies remain unresolved. It has been suggested that in situ production of the relevant bacterial GDGTs (within the lake’s water column or after burial in sediments) and/or diagenetic effects are likely to alter soil-derived GDGT-patterns in lake sediments. However, in a pilot study to this proposal (Niemann et al., 2011), we could show that specific environmental conditions (e.g., as encountered in the euxinic Lake Cadagno, Switzerland) may be particularly conducive to the preservation of original bacterial GDGT-signatures, so that the MBT/CBT paleothermometer can precisely resolve subtle temperature changes of < 1 °C. 
Here, we propose to test and calibrate the MBT/CBT-paleothermometer in lacustrine settings, with the particular goal to elucidate the processes that may perturb the direct reflection of primary soil signatures within the lake’s sedimentary archive. We plan i) to conduct GDGT measurements in catchment soils, sediment trap material and surface sediments from various Swiss lakes ii) to set up incubation experiments with soil and sediment samples under controlled laboratory conditions to study mechanisms of secondary GDGT-alteration, and iii) to apply the calibrated MBT/CBT thermometer to the Holocene sediments from central Switzerland. In the first stage of the project, we will compare GDGT-patterns in recent lake sediments with those in soils from the respective lake catchments. MBT/CBT -based T and pH estimates will be compared to instrumental data, which will permit us to determine the sensitivity and accuracy of the lacustrine MBT/CBT-paleothermometer under the given sedimentation/preservation conditions. The GDGT analysis of the sinking flux collected in sediment traps - representing the transient stage between soil organic matter genesis and burial in the lake basin - will allow further insight into the potential role of in situ production and secondary alteration of MBT/CBT-signatures. In the second part of the project, bacterial GDGTs will be studied in experimental setups where soils and sediments are exposed to different regimes of oxia and temperature. Here, we also plan to measure the relevant GDGTs not only as core-lipids but also as intact polar lipids (IPLs), which will allow us to discern dead (fossil) and viable sources of the target lipids. Results from the calibration study will finally provide the basis for GDGT measurements in a long sediment core from Lake Soppensee. The Holocene and Late Glacial record of T-variations from Lake Soppensee will be compared to other proxy-based T-records (e.g., from Lake Cadagno), and will allow constraints on the effect of large-scale climate perturbations on geographically adjacent regions, which are separated by a meteorological divide (i.e. the Alps). 
The proposed study will represent an important step forward in our efforts to reconstruct past climate variations from lake sediments using a lipid-based paleothermometer. In addition, it will yield paleoclimatic records that will be the first of their kind for Switzerland. These records may prove vital for revealing north- versus south alpine climate variation, as well as for the modelling and understanding Holocene climate perturbation in central Europe.

Weijers, J. W. H., Schouten, S., van den Donker, J. C., Hopmans, E. C., and Sinninghe Damsté, J. S.: Environmental controls on bacterial tetraether membrane lipid distribution in soils, Geochimica Et Cosmochimica Acta, 71, 703-713, 2007.

Niemann, H, Stadnitskaia, A, Wirth, SB, Gilli, A, Anselmetti, FS, Sinninghe Damsté, JS, Schouten, S, Hoppmans, EC and Lehmann, MF: Distribution of bacterial GDGTs in Holocene sediments and catchment soils of the high-alpine Lake Cadagno: applications of the MBT/CBT-paleothermometer , Climate of the Past


Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Identification and carbon isotope composition of a novel branched GDGT isomer in lake sediments: Evidence for lacustrine branched GDGT production
Weber Yuki, De Jonge Cindy, Rijpstra W. Irene C., Hopmans Ellen C., Stadnitskaia Alina, Schubert Carsten J., Lehmann Moritz F., Damste Jaap S. Sinninghe, Niemann Helge (2015), Identification and carbon isotope composition of a novel branched GDGT isomer in lake sediments: Evidence for lacustrine branched GDGT production, in GEOCHIMICA ET COSMOCHIMICA ACTA, 154, 118-129.

Collaboration

Group / person Country
Types of collaboration
SUPSI Lugano (Dr. M. Veronesi and Dr. M. Simona) Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
- Exchange of personnel
Dr. A Gilli (ETHZ) Switzerland (Europe)
- Research Infrastructure
Organic Geochmistry Group at NIOZ (Prof. J. S. Sinninghe Damsté & Dr. A. Stadnitskaia) Netherlands (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure

Associated projects

Number Title Start Funding scheme
144960 XRF Core Scanner and digital radiography 01.01.2013 R'EQUIP
121861 Biogeochemical fluxes in South-Alpine Lakes: Linking nitrogen and methane dynamics in lacustrine redox-transition zones using a combined stable isotope and molecular approach 01.12.2008 Project funding (Div. I-III)
162414 Lacustrine in situ production and stable carbon isotope dynamics of branched GDGTs 01.10.2015 Project funding (Div. I-III)
121909 FloodAlp! Frequency and intensity of extreme floods in the Alps through the Holocene and implications for natural hazards in future climate scenarios 01.12.2008 Project funding (Div. I-III)
131870 Alteration of isotopic signatures during organic matter degradation (ISOALT) - Nitrogen in aquatic environments 01.02.2011 Project funding (Div. I-III)
131407 Holocene Paleoclimate Reconstruction of Southern Switzerland: Testing the MBT/CBT Paleothermometer on Lake Sediments (Lake Cadagno, Switzerland) 01.03.2010 International short research visits

Abstract

Of paramount importance for our comprehension and simulation of recent and future climate change is the precognition of climate variations in Earth’s history, yet instrumental and reliable historical data are only available for the last few centuries. For times scales beyond this very recent past, climate variations can be reconstructed with the aid of proxy-indicators in climate archives such as ice sheets, spelotherms, as well as aquatic sediments. Albeit the importance of the terrestrial realm in the global climate, paleoclimatological research traditionally focused on marine sediments. Typically, these span very long time periods, but they are rarely suitable to resolve sub-millennial time scales. Where they exist, the continental temperature (T) reconstructions are often limited to relative T fluctuations. A promising approach to go beyond the qualitative assessment of T variability in the past is to use a temperature-proxy, which is based on the analysis of (presumably) soil-bacterial lipids preserved in sedimentary archives, and which allows for absolute T reconstructions. This paleothermometer relies on the relative abundance of methyl-branched and cyclic dialkyl glycerol tetraethers (GDGTs) (i.e., MBT/CBT-indices), which changes in response to mean annual air temperature (MAAT) (Weijers et al. 2007a). In addition to information on MAAT, MBT/CBT-measurements allow for the reliable assessment of soil-pH, which can be a qualitative indicator of climate wetness. Similar to marine sediments, lake sediments are important geological archives, which may span time intervals from thousand to hundred thousands of years, and, hence, have a high potential for portraying long-term terrestrial climate variations. While MBT/CBT-ratios were successfully used to reconstruct mean annual air temperature (MAAT) from soils, the applicability of this paleothermometer to lacustrine sediments needs substantial testing. To date, for example, most of the existing MBT/CBT-measurements from modern lake sediments seem to consistently underestimate observational T-data, yet the mechanisms behind the observed discrepancies remain unresolved. It has been suggested that in situ production of the relevant bacterial GDGTs (within the lake’s water column or after burial in sediments) and/or diagenetic effects are likely to alter soil-derived GDGT-patterns in lake sediments. However, in a pilot study to this proposal (Niemann et al., 2011), we could show that specific environmental conditions (e.g., as encountered in the euxinic Lake Cadagno, Switzerland) may be particularly conducive to the preservation of original bacterial GDGT-signatures, so that the MBT/CBT paleothermometer can precisely resolve subtle temperature changes of < 1 °C. Here, we propose to test and calibrate the MBT/CBT-paleothermometer in lacustrine settings, with the particular goal to elucidate the processes that may perturb the direct reflection of primary soil signatures within the lake’s sedimentary archive. We plan i) to conduct GDGT measurements in catchment soils, sediment trap material and surface sediments from various Swiss lakes ii) to set up incubation experiments with soil and sediment samples under controlled laboratory conditions to study mechanisms of secondary GDGT-alteration, and iii) to apply the calibrated MBT/CBT thermometer to the Holocene sediments from central Switzerland. In the first stage of the project, we will compare GDGT-patterns in recent lake sediments with those in soils from the respective lake catchments. MBT/CBT -based T and pH estimates will be compared to instrumental data, which will permit us to determine the sensitivity and accuracy of the lacustrine MBT/CBT-paleothermometer under the given sedimentation/preservation conditions. The GDGT analysis of the sinking flux collected in sediment traps - representing the transient stage between soil organic matter genesis and burial in the lake basin - will allow further insight into the potential role of in situ production and secondary alteration of MBT/CBT-signatures. In the second part of the project, bacterial GDGTs will be studied in experimental setups where soils and sediments are exposed to different regimes of oxia and temperature. Here, we also plan to measure the relevant GDGTs not only as core-lipids but also as intact polar lipids (IPLs), which will allow us to discern dead (fossil) and viable sources of the target lipids. Results from the calibration study will finally provide the basis for GDGT measurements in a long sediment core from Lake Soppensee. The Holocene and Late Glacial record of T-variations from Lake Soppensee will be compared to other proxy-based T-records (e.g., from Lake Cadagno), and will allow constraints on the effect of large-scale climate perturbations on geographically adjacent regions, which are separated by a meteorological divide (i.e. the Alps). The proposed study will represent an important step forward in our efforts to reconstruct past climate variations from lake sediments using a lipid-based paleothermometer. In addition, it will yield paleoclimatic records that will be the first of their kind for Switzerland. These records may prove vital for revealing north- versus south alpine climate variation, as well as for the modelling and understanding Holocene climate perturbation in central Europe.Weijers, J. W. H., Schouten, S., van den Donker, J. C., Hopmans, E. C., and Sinninghe Damsté, J. S.: Environmental controls on bacterial tetraether membrane lipid distribution in soils, Geochimica Et Cosmochimica Acta, 71, 703-713, 2007.Niemann, H, Stadnitskaia, A, Wirth, SB, Gilli, A, Anselmetti, FS, Sinninghe Damsté, JS, Schouten, S, Hoppmans, EC and Lehmann, MF: Distribution of bacterial GDGTs in Holocene sediments and catchment soils of the high-alpine Lake Cadagno: applications of the MBT/CBT-paleothermometer , Climate of the Past
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