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The promise of emerging molecular indicators of climate change at Lake El’gygytgyn

Explore the potential of emerging molecular indicators to study climate change at Lake El'gygytgyn, including changes in organic matter sources, temperature structure, mean annual soil temperature, precipitation patterns, and evaporation/precipitation balance.

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The promise of emerging molecular indicators of climate change at Lake El’gygytgyn

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  1. The promise of emerging molecular indicators of climate change at Lake El’gygytgyn Steven Petsch, Kenna Wilkie & Julie Brigham-Grette – UMass, Amherst Sabine Hanisch – AWI, Bremerhaven

  2. Depth plots of physical properties, organic and isotope geochemistry, and major lithological characteristics of core PG1351 indicating warm (unit 1), peak warm (unit 2), cold and dry (unit 3), and cold and more moist (unit 4) climate modes at Lake El’gygytgyn (from Melles et al., 2007)

  3. Expanding the uppermost 270 cm (approximately 60 kyr), we see fine texture to %TOC and d13CTOC record, at approximately 400 year resolution. • Outstanding questions: • What are the dominant sources of organic matter [OM] to Lake El’gygytgyn sediments? • What changes in OM source and/or preservation are responsible for 8-fold increase in TOC during LGM? • What changes are indicated by the simultaneous ~ 4 ‰ drop in bulk d13CTOC during LGM? • What critical climate variables (temperature, precipitation patterns, regional humidity) can be recovered?

  4. Potential climate variables available through Lake El’gygytgyn biomarkers: I. Lake water column temperature structure • TEX86 • a tetraether index based on the relative amount of cyclopentane-containing glycerol dialkyl glycerol tetraethers (GDGTs) • developed from samples in the marine environment • Lake El’gygytgyn “TEX86” temperatures are approximately 5±1.4 °C • because TEX86 in lakes records temperature at/near base of thermocline, lake-based TEX86 temperatures not expected to vary within Lake El’gygytgyn sediments. Source:Schouten et al., 2002

  5. Potential climate variables available through Lake El’gygytgyn biomarkers: • Mean annual soil temperature [MAT] • (from Weijers et al. 2007) • MBT and CBT indices • tetraether indices based on the extent of methylation (MBT) and cyclization (CBT) of tetraether membrane lipids common to soil microbiota • not yet tested or explored for high latitude environments – may show bias towards summer temperatures during soil biota growing season

  6. Results for Late Pleistocene and Holocene Congo Basin show marked increase in tetraether lipid-based MAT at ~16 ka. (from Weijers et al., 2007) Warming (or greater export of soil from warm regions) in Congo Basin at ~16 ka

  7. Potential climate variables available through Lake El’gygytgyn biomarkers: • changes in precipitation delivery to Lake El’gygytgyn • biomarkers of aquatic plankton: • C17 & C19n-alkanes, dinosterol, C16-C20n-alcohols • lipids in aquatic plankton faithfully record the dD of the water in which they are growing (from Huang et al. 2002) • will be attenuated by water residence time in the lake (D/H)sample – (D/H)std dD (‰) = x 103 (D/H)std

  8. Potential climate variables available through Lake El’gygytgyn biomarkers: • changes in precipitation deliver to Lake El’gygytgyn • biomarkers of terrestrial plants: • C25 – C35n-alkanes, sitosterol, stigmastanol, C16-C26n-alcohols • lipids in plants reflect the dD of “leaf water”, which is significantly related to both growing season precipitation dD values and to growing season humidity

  9. Potential climate variables available through Lake El’gygytgyn biomarkers: • changes in growing season evaporation/precipitation balance at Lake El’gygytgyn • the offset (DdD) between aquatic biomarker dD values and coeval terrestrial biomarker dD values will reflect - differences in the source of summer vs winter precipitation to Lake El’gygytgyn - the intensity of summer growing season humidity and evaporation/precipitation balance

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