Among six EEPS majors graduating this spring, four completed honors research to receive Distinction in Research and Creative works. Read on for highlights of their effort and where they are headed next.
Lingkun Guo, with advisor Laurence Yeung, conducted research using clumped isotopes of oxygen. In her thesis titled “Oxygen Isotope Fractionation During Cyanobacterial Photosynthesis”, Guo wanted to understand how different isotopes of oxygen are processed by cyanobacteria in order to begin to address quantifying the contribution of atmospheric oxygen through marine primary productivity.
“I became really interested in the topics of nutrient cycling in the ocean and the interaction between oceans and the climate system after taking a course on Oceans atmospheres and climates. I also worked in the Stable Isotope Lab during my junior year, so I wanted to work on a project that could combine my interests in ocean biogeochemistry and the use of stable isotope methods.”
In a set of controlled laboratory experiments, she studied the effect of nutrient availability, in this case nitrate, on the ratio of oxygen isotopes produced by freshwater cyanobacteria during photosynthesis.
Her biggest challenge was learning how to deal with experiments that took a lot of time, but would often generate results that were less ideal.
“I had to learn how to be persistent and patient in the lab, especially when things didn’t go well. I loved the fact that the project gave me the opportunity to use many different instruments for the various measurements I needed to make. It was really fun to learn different techniques and methods in the lab.”
Guo’s results provide important constraints to on the behavior of ‘clumped’ isotopes of oxygen for interpreting broader heterogenous clumped isotope patterns observed in nature. She is headed off to Princeton to study geosciences in the fall.
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Emilia Pichon, was advised by Sylvia Dee, was very interested in climate science and the impacts of climate change on society. She looked to study hurricanes as a way to address that important issue.
Pichon’s research, titled “Changes in Atlantic Tropical Cyclones and the Bermuda High: Clues from the Last Millennium to Inform the Future,” would evaluate the products of two climate models to better understand the relationship between the phenomenon known as the Bermuda High and its relationship with hurricane characteristics over the last 1000 years.
As 20th century data sources are limited given the brevity of the satellite era, Pichon used datasets produced by the Last Millennium Reanalysis and the Community Earth System models to analyze the strength and position of the Bermuda High, which influences hurricane track and the currents that steer them.
“The biggest challenge was gaining a sense of the bigger picture despite the size of the dataset used for the project. I really enjoyed the creativity associated with generating the datavisuals and how climate models are used to study specific problems. “
By comparing various Bermuda High indices (BHI) defined by previous studies, she generated maps of sea level pressure anomalies and hurricane tracks during years with high vs. low BHI values. Her results provide a better understanding of the relationship between the Bermuda High and hurricane characteristics over the last 1000 years, and will provide better context for hurricane prediction in the future.
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Stella Potemkin worked with Cin-Ty Lee on phosphorous in arclogites and what role it may play in the global phosphorous (P) cycle evolution throughout Earth’s history. Potempkin’s research titled “Understanding Phosphorus Mobility in Arclogites”, looks at P mobility in continental arc settings. Arclogites are unique rocks associated with volcanic arcs produced at convergent plate margins associated with subduction zones.
Phosphorus is an essential element to the development of life on Earth, but its availability is limited. While much is known about P fluxes at Earth’s surface, little work has been done to understand how P is cycled through igneous systems, specifically at subduction zones.
“I discovered that I really enjoy igneous petrology and geochemistry. My favorite aspect about Earth science research is how interdisciplinary it can be and how it can have implications for so many other fields of study. I think that's what drove me towards a thesis that focuses on a part of the Earth system but also has greater connection to things like nutrient availability and life history.”
Potemkin analyzed the mineral chemistry and quantified the whole-rock bulk mineral volume of the various phases for several arclogite samples with bulk P greater than 0.2 wt%. “Using the EPMA, looking at the backscatter electron images for my samples and seeing the minerals we measured the chemistry of was a cool experience."
The results identified apatite and titanite as the current main carriers of P, but other minerals, such as garnet, might also play an important role, potentially as an early P reservoir, which implies a more complicated evolution for the rock and thus cycling of phosphorous.
“The big challenge during my project was framing unexpected results as new opportunities.”
The study demonstrates that arclogites have a dynamic history that needs to be investigated further. Potemkin outlined potential pathways forward, including expanding her approach to more samples, and exploring arclogites from other parts of the world.
Stella will take a gap year, moving back to Colorado to work and travel while applying to graduate school.
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Sarah Preston has been working with Kirsten Siebach for several years processing remote sensing data collected by Mars rovers. In her thesis titled “Differences between modern and ancient Martian grain size distributions may reveal different paleoatmospheric conditions and provenance,” Preston presented the results of a study that addresses Mars mysterious early atmospheric history and its role in shaping Mars surface both in the past and potentially in the present.
The ancient Stimson sandstone appears to have a coarser grain size distribution than the modern Bagnold dune, which Preston hypothesized may reflect a different atmospheric density at the time the Stimson was deposited, and perhaps be comprised of a different sediment provenance than the Bagnold.
For the project, she utilized imagery captured with rover instruments to characterize the grain size distribution and apply that to various transport mechanisms under differing atmospheric conditions.
Her results show that the Stimson grains are coarser than those of the modern Bagnold dunes. The mechanisms for that result work better under an early denser atmosphere with lower windspeeds that can move a greater range of grains. In order to get the observed fraction of larger grains in the Stimson, the starting materials had to be coarser and more abundant.
Sarah is headed to UCLA for graduate school this fall.
You can read their research abstracts HERE.