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Carbon capacity, continued

System stressors

Desai is also working in the central Rocky Mountains, a region plagued by persistent drought and a warming-induced spread in the frequency and intensity of pest outbreaks, particularly bark beetle infestations. The beetles have thrived through recent unusually mild winters, threatening the region’s evergreen forests. 

With support from the National Oceanic and Atmospheric Administration, Desai is measuring the atmospheric carbon concentration on the tops of mountains to study how these forest stressors have impacted carbon absorption. The findings will help guide projections of how carbon uptake could change in a world with an increased frequency of drought or pest outbreaks, or a decreased frequency of either. 

Galen McKinley. Photo: Jeff Miller/
UW-Madison

Galen McKinley, who studies how large bodies of water influence carbon cycling, is also investigating the impact of pest outbreaks on carbon uptake, but from an underwater perspective. 

In collaboration with Harvey Bootsma of the UW-Milwaukee School of Freshwater Sciences, McKinley is trying to better understand how quagga mussels are modifying Lake Michigan.

The invasive species has blanketed the lake bottom at a rate of about 10,000 mussels per square meter. The trillions of mussels gorge on phytoplankton, removing the primary food source for fish. 

McKinley and her lab of researchers are developing a hydrodynamic model that simulates circulation in the lake’s food web. By representing quagga mussels in the model, McKinley hopes to be able to demonstrate in more detail the mussels’ influence on nutrient and carbon cycling. 

“Their impact is so important that you can’t simulate the rest of the system without them; it becomes part of the lake chemistry,” McKinley says. Once the mussels are integrated into the model, she says, “You can start asking ‘what if’ questions like ‘what if we get rid of them’ or ‘what if acidification hurts them? What might warming do?’”

Ocean exploration

Acidification – a decrease in water pH as a result of carbon uptake – is another area of study for McKinley in both the Great Lakes and the global oceans. “As we put more carbon dioxide in the atmosphere, we drive more carbon into the water and that acidifies the water,” she explains. 

Ocean pH has fallen significantly since preindustrial times and continues downward, with a range of ecological impacts. McKinley suspects the same is true in the Great Lakes, but available datasets aren’t detailed enough to know for sure. 

This lack of data isn’t limited to acidification; as a whole the Great Lakes are understudied, she says. With Nelson Institute Environment and Resources student Jennifer Phillips (M.S. ‘12), McKinley has worked to encourage better monitoring of pH and other factors. 

In her research of the Great Lakes, McKinley draws from her extensive background in ocean physics. She’s been especially focused on how ocean carbon uptake is changing in the face of increasing atmospheric carbon. Her goal is to learn how much more carbon dioxide the oceans can pull from the air, particularly as the planet warms.

McKinley and colleagues recently published a nearly three-decade analysis of the rate at which the ocean is absorbing human-produced carbon by comparing the surface carbon content of the North Atlantic to atmospheric carbon trends from 1981-2009.

The report, funded by the National Aeronautics and Space Administration, provides some of the first evidence that the ocean is taking up less carbon because of climate change. Warm water can’t hold as much carbon dioxide, so rising temperatures weaken the ocean sink. 

As is true with the Great Lakes, limitations in ocean data are a major obstacle to research. As more data becomes available, McKinley can expand her analyses, using her findings to refine predictive models and future data collection. 

“That’s an area that a lot of people in CCR have worked on – trying to understand the future climate – but this brings in the carbon cycle component, which is still pretty nascent,” she says. 

“As we better observe the ocean carbon cycle, see changes and get more data, there’s going to be a lot of new questions brought forward,” she says. “I don’t see any limitation on the questions that can be asked. That’s one of the reasons I love oceanography – it’s a brave new world.”  

Novel partnership trains students as climate scientists 

When Ankur Desai measures greenhouse gases in northern Wisconsin forests, he’s not just helping to illuminate how ecosystems modify climate. He’s also igniting the spark of scientific inquiry in local students. 

For two years, Desai has coordinated with the College of Menominee Nation in Keshena to bring students into the field as climate researchers. The multi-day course is supported by a five-year National Science Foundation grant that includes an outreach component. 

College of Menominee Nation students measure carbon
dioxide levels of soil in a maple forest near Minocqua for
Desai's field course. Photo: Bryce Richter/UW-Madison

“The Wisconsin Idea compels us to make sure our research and teaching benefits the entire state. For me, doing research in northern Wisconsin, it was important to work with people who live and study there,” says Desai, an associate professor of atmospheric and oceanic sciences and affiliate of the Nelson Institute Center for Climatic Research (CCR). 

“CCR is a research-oriented center, but we’ve been learning over time that our mission is useless if we’re not communicating that knowledge broadly and widely, and not just to experts in science,” he continues. 

While participants contribute to Desai’s field observations, his larger goal is to expose the students to scientific careers. The project targets community college students who might want to pursue advanced degrees in environmental science.

“The more you get students doing hands-on science, the more you pique their interest in potentially doing this as a career,” he says. “The most important part of this outreach is that the students are in a community of other scholars and they’re getting to meet scientists.” 

Desai brings his own students along to describe their experiences. 

“Every student has their own story about how they got into the field, what struggles they had, how their research is going,” he says. “For the Menominee students to learn those stories and for them to share their own, it really helps everyone get a better understanding of what’s going on there, which can undoubtedly improve research.”