Microscopic plants in the ocean, called phytoplankton, are responsible for about half of the solar-powered photosynthesis on Earth. As they grow and reproduce, phytoplankton take up dissolved carbon dioxide (CO2) from the surface ocean, where it is in balance with atmospheric CO2 gas, and convert it into solid organic carbon. When they die, this organic matter sinks into the deep ocean, and is converted back to dissolved CO2 via grazing by other plankton and bacteria. This process, called the biological pump, removes CO2 from the surface ocean-atmospheric reservoir and transfers it to the deep ocean, where it may be trapped for several hundred, or even thousand, years.
The biological pump is pivotal to Earth’s climate. Without it, pre-Industrial Revolution levels of atmospheric CO2 would have been more than 50% higher than observed, while today the oceans have already absorbed about 30% of human CO2 emissions. A key goal of my research is to understand the controls on the efficiency of the biological pump, in the modern, past and future ocean, and the implications for Earth's climate.
I am an isotope geochemist, interested in developing novel isotopic tracers of carbon cycling in the past and present ocean. My tools are the isotopes of various trace metals (including copper, zinc, cadmium). These elements are micronutrients, which are essential in small amounts for life.
et al., 2021, Bioactive Trace Metals and Their Isotopes as Paleoproductivity Proxies: An Assessment Using GEOTRACES‐Era Data, Global Biogeochemical Cycles, Vol:35, ISSN:0886-6236
et al., 2021, Cold-water corals as archives of seawater Zn and Cu isotopes, Chemical Geology, Vol:578, ISSN:0009-2541, Pages:1-20
et al., 2021, Towards balancing the oceanic Ni budget (vol 547, 116461, 2020), Earth and Planetary Science Letters, Vol:557, ISSN:0012-821X
Sherman DM, Little SH, 2020, Isotopic disequilibrium of Cu in marine ferromanganese crusts: Evidence from ab initio predictions of Cu isotope fractionation on sorption to birnessite, Earth and Planetary Science Letters, Vol:549, ISSN:0012-821X
et al., 2020, Towards balancing the oceanic Ni budget, Earth and Planetary Science Letters, Vol:547, ISSN:0012-821X