UT-Austin researchers make progress toward understanding climate change

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Photo Credit: Courtesy of Kaustubh Thirumalai

Analyzing marine sediment samples collected from the Gulf of Mexico, scientists are gathering information to make new connections about climate change.

Dr. Terrence Quinn, director of the University of Texas Institute for Geophysics, said one of the key things scientists need to better communicate with the general public is that climate change starts with the ocean. One issue is that scientists are still understanding how it all starts. A study published on Jan. 26 in Nature Communications places scientists one step closer to putting all the pieces together.

“Our knowledge of ocean currents, circulation patterns, and how they have varied over the last millennium is fragmentary at best,” said Dr. Kaustubh Thirumalai, a postdoctoral researcher at Brown University and first author of the study.

The study, conducted at the institute during Thirumalai’s time at UT-Austin as a graduate student, shows that a correlation exists between surface-ocean circulation in the northern Atlantic Ocean and climate in the Northern Hemisphere. In terms of climate change, this will help scientists better understand climate variability and the resilience of regional climate systems to ongoing climate change, Thirumalai said.

Surface circulation in the Atlantic Ocean is integral to global climate change, facilitating heat transport between the hemispheres, according to the paper. In addition, large currents in the northern Atlantic are known to travel through the Gulf Stream into the Gulf of Mexico, into Florida, and then back through the Gulf Stream and to the northern Atlantic, Quinn said.

With this information, scientists generated records of ocean properties, and the next step was to start comparing them to others.

“You sort of build the pyramid from the base like that,” Quinn said. “We said, ‘Okay, well we know from the observations that we have global connections, and now let’s see how far (they) go.’”

Thirumalai reconstructed past oceanic parameters, like temperature and salinity, from sites yielding high-sample resolution — meaning each sample is an average over 30 to 50 years — and used that to determine how ocean circulation changed in the past, Thirumalai said. From those samples, the researchers extracted information from the shell chemistry of foraminifera, a type of plankton.

“The tricky thing is to understand what these changes at near-coastal sites can tell us about large-scale Atlantic Ocean circulation,” Thirumalai said. “(But) since our sample resolution was near 30-year increments, we were able to analyze modern decadal observations to help understand widespread links with our climate record developed from the Gulf of Mexico.”

Co-authors of the study included researchers from the U.S. Geological Survey and MIT, and research was supported by the NSF, National Oceanic and Atmospheric Administration, the Consortium for Ocean Leadership, the UT Jackson School of Geosciences and Brown University.

“This research could not have been completed without collaborations,” Thirumalai said. “In my experience, more diverse partnerships in science lead to better science, mainly due to more unique perspectives. I remind myself that the climate system doesn’t really have borders.”

This study was the result of the classic sort of science that starts with a small hypothesis, expands it, and sees how far it can push current boundaries, Quinn said.

“There’s always a bit of serendipity in all things that we do, especially in science,” Quinn said. “I consider myself blessed to have had someone as good as Khau be my graduate student, and together we were a great team.”

In addition, the earth and climate sciences are interactive and encourage scientists to work together, Quinn said.

“(It’s) a real bonus, and that helps us recruit graduate students here to UT because they know that they’re going to be able to work on these big problems and work with not just national, but international, partners,” Quinn said. “It’s a wonderful, symbiotic relationship that happens.”