Most visitors to the Caribbean hope that their stay won’t coincide with a major tropical storm.

Hyejung Lee hoped for exactly the opposite.

Last summer Lee, an earth sciences major at the University of Pennsylvania, traveled to Puerto Rico to “chase storms,” studying how rainfall and flooding impact carbon cycling from the atmosphere to the ocean, a process that is relevant to climate change. Enthralled with the subject and her field experience, she will pursue additional research in Puerto Rico next month. Her findings will form the basis of her honors thesis project.

Lee, a rising senior who hails from Seoul, has conducted her studies under the guidance of Jane Willenbring, an assistant professor in Penn’s Department of Earth and Environmental Science in the School of Arts and Sciences.

“Hyejung outlined her own project and got her own funding,” Willenbring says. “Last year she was looking at where the carbon in the system was coming from. Now she’s going to look at what factors cause carbon to become sequestered in flood plains.”

Lee began her exploration of earth science research her sophomore year by consulting the list of potential projects offered by the Penn Undergraduate Research Mentoring program. PURM allows professors to propose substantive research projects for first- and second-year students to complete during a summer break.

“I thought that would be a good opportunity for me,” Lee says. “Professor Willenbring had a few projects listed, and I applied for all of hers because I thought they were really interesting.”

During her trip to Puerto Rico in May of 2011, Lee’s investigation attempted to answer the question of whether stronger tropical storms — a byproduct of climate change — may lead to increased carbon sequestration in the ocean. She hypothesized that the storms’ heavy rainfall and flooding might trigger erosion of carbon-containing sediment into rivers and finally to the ocean bottom. There, it could become locked away, unable to contribute to growing carbon dioxide levels in the atmosphere.

To address these hypotheses, Lee and her fellow researchers eagerly awaited a storm to arrive. Within the first week of their trip, the group was “really fortunate,” Lee says, to be hit by a big storm. As the storm came through, Lee’s aim was to measure the suspended sediment and carbon content of the river water.

“We stayed up all night in front of a bridge over the river because we didn’t know exactly what time the storm would start. When it did, every 30 minutes or so we’d just grab big paint buckets and fill them up with sediment.”

To concentrate the sediment samples, Lee hefted the weighty buckets and poured them through filter paper. Once back at Penn, she could analyze what remained on the filter paper to determine the amount of carbon present.

“I need a lot more data,” Lee says, “but we could see trends that agreed with some of the papers I had read.”

Though her studies indicated that more flooding actually led to less carbon concentration in the sediment samples, she’s unsure if that is an artifact of her site selection, the small sample size or dilution of carbon by sediment.

Although Lee has completed many aspects of the work independently, she’s been grateful for Willenbring’s advice throughout the process, from generating a research question to preparing the poster that showcased her results.

“Professor Willenbring is really available, which is great for students,” Lee says. “I also like how she doesn’t do everything for you, so you have to come prepared and with your own interests.”

Now Lee is reading up on relevant literature to prepare for her second trip to the Caribbean. Funded by the Center for Undergraduate Research and Fellowships, her research will examine how carbon is deposited and how it decomposes in flood plains.

Lee says that this year, she’ll be better equipped for the field experience.

“I’m hoping that I’ll take ownership more, I’ll take more initiative,” she says. “After coming back from the field last year I realized that not many students get to go on these trips; I was the only undergraduate there. So I hope this summer I’ll make the most out of the opportunity.”