My work focuses on understanding the evolution of Earth's oceans and climate in the past. The deep sea houses one of Earth's greatest archives of geologic history- layers and layers of mud that build up over time. I measure the chemistry of microfossils found in deep-sea sediments, called foraminifera, to reconstruct changes in ocean carbonate chemistry, such as carbon dioxide content, through time. We also grow foraminifers in the laboratory in order to make calibrations that we can apply to records of past climate.
My current projects include:
1) Interpreting Records of Ocean Acidification from the Paleocene-Eocene Thermal Maximum: Insights from Culture Experiments
Around 56 million years ago, a profound amount of isotopically depleted carbon was released into the ocean-atmosphere system during an event called the Paleocene-Eocene Thermal Maximum (PETM). Often touted as our closest "analog" to modern carbon dioxide release and warming, this perturbation caused widespread ocean acidification, as recorded by two boron-based proxies in planktic foraminifera- boron isotope and B/Ca ratios. To quantitatively interpret B/Ca records at the PETM, we have undertaken a series of laboratory culture calibration experiments where we grew foraminifera across a wide pH range in seawater chemistry that mimics that of the Paleocene Ocean. We are also exploring other potential controls on the B/Ca proxy so that we can more accurately apply it to past periods of ocean acidification.
2) Deep Ocean Carbon Dynamics and Ocean Circulation across the Mid-Pleistocene Transition
The Mid-Pleistocene Transition, which occurred from approximately 1.3 to 0.6 million years ago, remains an enigmatic period in Earth's paleoclimatic history. During this interval, glacial-interglacial cycles transitioned from 40,000-year to 100,000-year pacing without a change in external solar radiation forcing. We are collaborating with large group of researchers using both foraminiferal trace element proxies and neodymium isotopes to investigate the links between ocean circulation and carbon storage in the deep ocean across this time period.