Research

The research in my lab focuses on the use of biomarkers in paleoclimate ("molecular paleoclimatology"). Biomarkers are diagnostic fossil fats produced by algae, microbes, higher plants, and animals. They can be well preserved in sediments and rocks for millions and even billions of years. However, most of my research focuses on relatively recent timeframes (geologically speaking) such as the Late Quaternary Period and the last few millennia. From the biomarkers, it's possible to infer past changes in a number of important climatic and biogeochemical variables including temperature, precipitation, vegetation change and microbial productivity. An overview of these molecular tools is given below.

In addition to measuring biomarkers and creating paleoclimatic data, my research aims to synthesize the data with other types of proxies as well as climate models. I collaborate with both modelers and climate dynamicists to construct model-proxy comparisons from which we can learn important aspects of the climate system. Recent work has addressed climatology in East Africa, Indonesia, and the glacial tropical Indo-Pacific.

For information on specific projects, check the submenu at left.

GDGTs

flexible
GDGTs (glycerol dialkyl glycerol tetraether) are produced by Archaea (and some unknown types of Bacteria) and can be used for paleotemperature reconstruction. I have applied the isoprenoidal GDGT proxy TEX86 to lacustrine settings to reconstruct temperatures in East Africa both in ancient and relatively recent times. Since 2009, I have been researching the applicability of branched GDGTs towards paleotemperature reconstruction in lakes, including formulating calibrations and investigating non-temperature environmental influences. Ongoing research focuses on the development of new statistical approaches towards lipid paleotemperature calibration.

Leaf wax isotopes

flexible
The stable hydrogen and carbon isotopic composition of leaf wax compounds can be used to infer past changes in precipitation and vegetation. Leaf waxes can be isolated from both near-shore marine and lacustrine sediments anywhere on Earth, providing a near-universal proxy for terrestrial climate change. Furthermore, leaf wax isotope reconstructions can be used in tandem with isotope-enabled modeling experiments to look at complex aspects of the hydrological cycle going back through time. I have used leaf wax isotopes, primarily hydrogen isotopes, to reconstruct changes in the hydrological cycle in Africa and Indonesia.

Alkenones

flexible
Alkenones are long-chain ketone compounds produced by haptophyte algae like Emiliana huxleyi. The relative unsaturation of these compounds is a very precise proxy for sea-surface temperatures that has been used in paleoceanography for over 30 years. Some of my new projects use alkenones in marine sediment cores to infer past SST changes that may have influenced the tropical hydrological cycle.