Caves, Climate and Cycling: UT Alumna Barbara Wortham

Barbara Wortham

When Barbara Wortham rode out of Boston to start her doctorate at the University of California at Davis, she was on her bicycle.

“At first, it was really long days: getting through the Adirondacks was pretty difficult, and it took 3.5 weeks to get to Chicago,” says Wortham, a 2013 graduate of the Environmental Science Program (EVS) at The University of Texas at Austin. “I think more women should do things like this—ride solo—because it was definitely an empowering experience.”

Wortham is currently researching the record of dry and wet years over the last 20,000 years by analyzing stalagmites created through slow calcite precipitation in caves—continuing a volume of research that started in her undergraduate years in Austin.  She recently answered questions about her academic path, research interests, and, of course, cycling.

What do you remember most about your undergraduate time in EVS?

It is so awesome that EVS is blossoming into the bigger thing that it was. The program was really new when I was an undergraduate. It was really fun: there were 20 of us, so we really bonded and had a lot of contact with people at the Environmental Science Institute. The field work that we did totally inspired me to continue cave work. As an undergraduate research assistant, I helped monitor local caves every month for two years. Monitoring is important because each cave responds to rain events in different ways which has implications for stalagmites that develop.

One thing that I want to communicate is that undergraduates at UT have opportunities that don’t exist elsewhere: they can take advantage of the geology they learn in the program and immediately turn these skills into internships. I also did internships at the Texas Commission on Environmental Quality and with a private consulting firm CDM Smith.

What was your next step after UT Austin?

I went to Boston College to continue to work with Corinne Wong for my Masters. We worked in Brazil to reconstruct monsoons—typically in January and February—over the past few thousand years at a really high resolution. We wanted to see if monsoon strength changed since the Industrial Revolution. We looked at strontium isotopes left in the stalagmites in caves and found that the amount of precipitation falling in central Brazil has been getting stronger over last two thousand years.  This may be related to an increase in monsoon strength which may in turn be related to climate change (although it is difficult to assign a driver to these large-scale changes).  

How do you collect climate data from a stalagmite?

Stalagmites grow like a tree with a ring every season for thousands and thousands and thousands of years. They grow from the cave floor, and each layer holds a record of the local climate that year through the physical and chemical signals archived. When we collect, we make certain that the stalagmites are well preserved—not knocked over or scratched. Stalagmites stop growing if touched regularly or muddy because the organics make it so that the calcite cannot precipitate out and stick as they would normally. We collect the sequence in different ways, depending on how big the stalagmite is. We either core it like an ice core, or collect it out of the cave, saw it in half and put the other half back into the cave.

What are you currently researching?

We are collecting data from caves in the Western Sierra Nevada. We have some really exciting preliminary data on cold and warm periods since the last glacial maximum. The warm periods act like the Holocene—a stable and warm period—which may be due to precipitation forcing or causing drought cycles to be longer during warm periods. We are using quantitative proxies that are different from the stable isotopes of calcite that many others use. We use fluid proxies, or water that is trapped in the stalagmite calcite. Noble gas concentrations in the fluid help us get at temperature, and we use stable isotopes in the fluid to understand precipitation.  With these proxies, we are hoping to be able to compare our data better with climate models over the same period.

What do you enjoy outside of caves?

I do a lot of century rides on my bicycle, riding various pieces up and down the California coast.


Author: Kristin Elise Phillips, Communications Coordinator, Office of Sustainability