How does the interplay between ocean circulation and biological processes govern the cycling of nutrients in the sea?
As an isotope geochemist with a strong interest in global-scale ocean biogeochemistry, I use stable isotope tracers to study this interaction, in research that is funded by the Swiss National Science Foundation with support from the US National Oceanic and Atmospheric Administration.

My research in Prof. Jorge Sarmiento's ocean biogeochemistry group at Princeton combines observational isotopic data with ocean general circulation model studies to gain a process-based understanding of the controls on oceanic stable isotope distributions, specifically the stable isotopes of silicon, an element that is vital to the growth of siliceous phytoplankton such as diatoms.

Observations:

A section through the southeastern Pacific Ocean at 103W, showing the propagation of the Si isotope signal of utilisation from the surface Southern Ocean far into the subtropics in the salinity minimum of SAMW/AAIW. These observations were published by de Souza et al. (2012) in Biogeosciences.

Model:

Results from an ocean general circulation model simulation (MOM3 P2A) that deconvolves Si into its preformed and regenerated components. The plots show the isotopic composition of total dissolved Si and these two components at a model depth of ~2000m. From the modelling study of de Souza et al. (2014).