This project is in
collaboration with Pat Anderson (Quaternary Research Center, University of
Washington) and Beverly Johnson (Bates College). The D/H and 13C/12C of lipids extracted
from the sedimentary record of lakes in the Siberia will be measured. These measurements will be used to
reconstruct changes in the lake’s hydrologic and carbon balances since the Last
Glacial Maximum (LGM). These isotopic
reconstructions of changes in the paleoenvironment will be compared to the
paleoclimate changes inferred from the existing pollen stratigraphies for each
lake. A portion of the proposed
research involves testing how well the isotopic composition of specific lipids
track changes in the isotopic composition of the water and dissolved inorganic
carbon in modern lakes. Based on these
results a determination will be made about how well the lipid proxy works. Additionally, modern day measurements will
be used to identify the most promising aquatic lipid biomarkers that will be
selected as proxies to reconstruct the changes in the hydrologic and carbon
budget of the lakes back to the LGM.
To accomplish these
objectives compound-specific GC/C/IRMS method will be used for the 13C/12C
and D/H measurements of individual lipids extracted from plants and
sediments. Continuous flow in-line
combustion or pyrolysis for 13C/12C or D/H, respectively,
will allow nanomolar quantities of lipids to be measured. GC and GC/MS techniques will be used to
quantify and identify the lipids.
It is expected that the
proposed research will accomplish the following.
•
Reconstruct the temporal changes in the δD of water for lakes and
the temperature changes needed to yield these δD changes. Compare the paleoclimate conditions that
would yield these temperature changes to the paleoclimate conditions inferred
from the pollen stratigraphy in these lakes.
•
Reconstruct the temporal changes in the 13C/12C of
terrestrial plants from measured changes in the 13C/12C
of terrestrially plant produced lipids and macrofossils of a single species
extracted from lake sediments.
Determine the consistency of these two proxies and how the paleoclimate
conditions that yield 13C/12C changes compares to the
paleoclimate conditions inferred from the pollen stratigraphy of these lakes.
•
Reconstruct the temporal changes in the carbon budget of two lakes from
measured changes in the 13C/12C of aquatic plant produced
lipids extracted from lake sediments.
Compare this reconstruction with changes in the hydrologic budget and
paleoclimate conditions inferred from the pollen stratigraphy of these lakes.