Environmental Internship Program - 2019 Booklet

Margaret Lynch ’21
GEOSCIENCES
CLIMATE CHANGE AND
ENVIRONMENTAL SCIENCE
PROJECT TITLE
Reconstruction of
Southern Ocean Nutrient
Concentrations During
Previous Interglacial
Periods
ORGANIZATION(S)
Sigman Lab, Department
of Geosciences,
Princeton University
LOCATION(S)
Princeton, New Jersey
MENTOR(S)
Daniel Sigman, Dusenbury
Professor of Geological
and Geophysical Sciences,
Professor of Geosciences;
Ellen Ai, Ph.D. candidate,
Geosciences
I prepared and analyzed diatom-bound
nitrogen in a sediment core from the Atlantic
sector of the Southern Ocean in order to
reconstruct nutrient conditions during glacial
and interglacial periods. After preparing these
samples using a variety of physical, chemical and
biological techniques, their nitrogen contents
were measured on a mass spectrometer. The
resulting isotopic signatures were then used to
reconstruct the efficiency of past diatom nitrogen
utilization. This record has great significance
as it provides insight into the release of carbon
— which is closely coupled with nitrogen in
marine processes — into the atmosphere from
Southern Ocean overturning. By examining
the processes that controlled this overturning
and their effects on Earth’s climate in the past,
we can better understand current and future
Southern Ocean overturning and carbon release.
Throughout this project, I learned about stableisotope
geochemistry, the nitrogen cycle, and the
research process, while acquiring new analytical
and technical laboratory skills. This project has
strengthened my interest in geochemistry and
climate science.
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