Application of organic geochemistry
to paleoceanographic studies

Over the past decade I have worked to develop and apply UK'37 to estimate past sea surface temperature (SST). When the technique was proposed in the mid 1980’s it still needed to be calibrated, its sources determined, and the stability of the resulting temperature record assessed before it could be reliably applied world-wide to paleoceanographic questions. My development work on C37 alkenones addressed each of these issues. By applying UK'37 to paleotemperature estimation, my multi-proxy work helped to establish that alkenone-based temperature estimates are robust and produce late Quaternary temperature records in the Atlantic, Pacific, and Southern Oceans. Recent studies have shown the radiocarbon ages of alkenones and foraminifera in sediments differ, suggesting that post depositional lateral transport of the organic fraction may be important in some locations. Presently, I am funded to re-examine the veracity of the alkenone record in the sediments by determining the 14C ages of sedimentary alkenones in areas of varying flow regimes on the sea floor. I continue to work with alkenone temperature estimation in modern samples to elucidate the controls on temperature proxies as they are produced. I am comparing the relative timing of the fluxes and the temperature estimates of UK'37 with foraminiferal-based techniques (assemblages and δ18O), along with additional biomarkers and bulk fluxes in sediment traps. My results show that the differences between the responses of each of these biologically based estimates suggests that the organisms responds differently to their environment and this impacts temperature reconstructions across climatic shifts. We are presently applying our new understanding of these productivity differences to down-core paleo-studies to better interpret the offsets in timing between different proxies and their impacts on paleoclimatic records.

New Zealand Map   We have sediment traps deployed on the Chatham Rise that have been collecting a time series of fluxes for the last decade. Chatham Rise Sea Surface Temperature We are interested in the Chatham Rise because the temperature changes dramatically across the rise from Subtropical waters to the north and Subantarctic waters to the south. Wet Chemistry After collecting the samples from the traps we process the samples. The samples are shared out to different labs, and we collect the fractions we are interested in.  In our lab we focus on the lipid portion of the organic matter. Injecting a Sample   After processing the sample we analyze it on a gas chromatograph (GC) or a GC-mass spec to determine its composition.