By Chelsea Zhao
Medill Reports
Crystal Rao, a geoscience graduate student at Princeton University, bases her research on environmental changes and impacts on species using nitrogen isotopes in fossils.
Rao uses the ratio of two common forms of nitrogen as a standard and compares it with the nitrogen inside the tooth tissue of the megalodon shark.
From there, she reconstructed a picture of when and where megalodon sharks topped the food chain in Arctic waters. Rao said this fierce predator could “basically eat anything in the ocean.”
Yet this species of shark, roughly 50 feet long, went extinct 3.5 million years ago. Rao said the food source the sharks relied on to fuel their massive bodies caused their downfall.
“As climate shifts, maybe the production in the ocean could change,” Rao said. “And depending on what the ecosystem responded to, there could be less food availability for those megalodon sharks.”
And that’s where the nitrogen fingerprint in the teeth comes in. The nitrogen isotope levels change in warm spells compared with ice ages so Rao can track climate change in the distant past.
Rao shared her research at the Comer Climate Conference this fall, an annual gathering of global climate scientists held virtually for the third year due to COVID-19. Comer conference veteran climate scientists, graduate students and post-docs investigate the effect of climate change from ancient life forms to theoretical models.
While Rao’s work examines a species belonging to an ancient era, another Comer scientist’s work takes estimation into the possibilities of the future.
Edmund Derby, a climate science Ph.D. student at Oxford University, utilizes simple models of Arctic sea ice from his past research in 2009 to examine the bifurcation, or tipping point, accompanying ice cover changes throughout the season.
Derby’s research presents climate from basic principles to its core behavior. In the scientific model, when atmospheric carbon dioxide exceeds a certain point, after all the Arctic ice melts, it is no longer possible to gain back the ice. His research presented at the conference investigates this tipping point under a model when the Arctic is covered in ice all year round.
“When you’ve reached this tipping point, you don’t get a reversible change once you’ve lost your ice cover,” Derby said.
The temperature of the Arctic is intrinsically connected with global warming across the rest of the world. In a phenomenon known as Arctic amplification, the Arctic warms twice as fast as the rest of the world, which has warmed in excess of 1 degree Celsius with global warming with the industrial age and emissions from petroleum-based fuels.
The ice has the light reflective property that redirects the heat. But as it melts, the heat-absorbent ocean water takes its place, according to Derby.
With heat transport to lower latitudes, as the Arctic warms up, the transfer of heat to the Arctic would be expected to decrease.
However, in a changing climate, the transport of water vapor or clouds into the Arctic can counteract the cooling of the heat transport. The water vapor causes local temperature in the Arctic to rise.
In his research, Derby is adding more factors into the model to make it more realistic to the Arctic ice cover and to investigate how the global rise of greenhouse gas will impact the ice melt at a local level.
Rao said in her field of geoscience, the past informs the present and the future. Studying the ancient past of Earth’s environment builds a better understanding of the complex systems involved.
“Only when we can really understand or estimate the future better, then we can come up with better plans in terms of how we do climate adaptation and climate mitigation,” Rao said.
Through Rao’s and Derby’s research of both the past and the future, concerns of climate change continue to loom in both the vanishing fabric of the Arctic and the demise of a species.
Chelsea Zhao is a Health, Environment & Science graduate student of journalism at Medill. You can follow her on twitter @chelseaqizhao
