2024 Internship Project
Dissolved oxygen concentration of the ocean has profound implications on the carbon and nitrogen cycles, imposing critical impacts on marine life and biogeochemical processes. Climate model simulations and recent observations suggest an expansion of the ocean’s oxygen-deficient zones (ODZs), linked to declining oxygen solubility under global warming. Studying the behavior of ODZs in response to past climate change would provide additional insights on the rates and trends of ODZ intensity to past global temperature changes.
Denitrification in the suboxic sediment porewaters and in the water column’s ODZs is the major fixed nitrogen removal mechanism from the ocean. Water column denitrification mainly occurs within the Arabian Sea and the eastern tropical Pacific ODZs, with the Arabian Sea ODZ accounting for about one-third of fixed marine nitrogen loss. Water column denitrification produces 15N enrichment in shallow subsurface nitrate, the upwelling of which leads to sinking particulate organic matter with a similarly high 15N enrichment. Therefore, stable isotope ratio measurements (δ15N ~15N /14N) made from paleoclimate archives from the Arabian Sea may provide insights on past denitrification rates, hence, the extent and the intensity of the Arabian Sea ODZ.
This project aims at reconstructing the Arabian Sea denitrification rates (hence, the ODZ behavior) over the past 200,000 years (back to the penultimate glaciation), with δ15N measurements made on foraminifera shell-bound organic matter (FB-δ15N) in sediment cores. The findings will provide a record of ODZ extent over glacial-interglacial cycles, with important insights on ODZs related to increasing global temperatures.
ORGANIZATION
Sigman Research Laboratory, Department of Geosciences
LOCATION
Princeton, New Jersey
Interns
Mentors
