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 research interests include:
1) Interpreting Records of Past Ocean Acidification Events from Foraminifera Proxies
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. I am currently using these new calibrations to generate a quantitative framework for interpreting past surface ocean acidification.
2) Deep Ocean Carbon Dynamics and Ocean Circulation across the Mid-Pleistocene Transition
During the Pleistocene epoch, Earth’s climate regularly swung in and out of glacial and interglacial periods. Approximately 1.3 to 0.6 million years ago, the pacing of these oscillations changed without any alterations in external solar radiation forcing. I am using the B/Ca proxy in benthic foraminifera to constrain changes to carbon storage in the deep Pacific and Atlantic oceans that may have helped to facilitate this transition. 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 critical time period.