Researchers from Dartmouth College have uncovered how fossil fuel emissions have profoundly impacted the Arctic’s atmospheric chemistry. Their findings show that pollution reaches the region in amounts large enough to alter its environment, challenging earlier assumptions about marine ecosystem health.
Published in Nature Geoscience, the study also highlights the effectiveness of air quality regulations in reversing these changes.
The research team, led by scientists from Dartmouth, studied ice cores from Alaska’s Denali National Park and Greenland to trace changes in atmospheric chemistry over centuries.
Ice cores, often described as time capsules, preserve gas bubbles, particles, and compounds from the past, offering a window into Earth’s climatic history. The key finding? A decline in methanesulfonic acid (MSA), a biomarker produced by marine phytoplankton, occurred shortly after the rise of fossil fuel combustion during the industrial era.
Phytoplankton, microscopic organisms in ocean ecosystems, play a crucial role in carbon cycling and marine food webs. Typically, MSA levels are used to indicate the productivity of these organisms. However, the Dartmouth team found that even as phytoplankton populations remained stable, MSA levels plummeted. This contradiction was tied not to a collapse in marine ecosystems, but to atmospheric pollution.
Air pollution alters the Arctic
Jacob Chalif, the study’s first author and a PhD student at Dartmouth, noted that the team observed a significant decline in MSA levels in Greenland’s ice cores beginning in the mid-1800s – just as Europe and North America were rapidly industrializing. Later, a similar drop was seen in Alaskan ice cores, coinciding with East Asia’s industrial boom.
“By releasing all this pollution into the world, we’re fundamentally altering atmospheric processes,” Chalif stated. “The fact that these remote areas of the Arctic see these undeniable human imprints shows that there’s literally no corner of this planet we haven’t touched.”
The drop in MSA was puzzling at first, but researchers soon realized that pollutants, particularly nitrate from fossil fuel emissions, were interfering with the natural production of MSA. Phytoplankton typically produce a compound called dimethyl sulfide, which can be converted into either MSA or sulfate. However, in areas with high levels of pollution, dimethyl sulfide is more likely to become sulfate, leading to a steep decline in detectable MSA, even without a corresponding crash in phytoplankton productivity.
For years, scientists had debated the significance of declining MSA levels in ice cores. Many believed that the drop indicated a major disruption in marine ecosystems, potentially due to climate change. But the Dartmouth team’s findings have turned that theory on its head. The problem wasn’t the ocean – it was the air above it.
The project began with the collection of a 700-foot ice core (in 2013) from Denali National Park and Preserve by Erich Osterberg, senior author of the study and associate professor of Earth Sciences at Dartmouth, along with his colleagues. The core, which dates back over a millennium, showed stable MSA levels for centuries – until the mid-20th century when it abruptly plummeted.
“When I saw that I had a Eureka! moment,” Osterberg explained. “Marine ecosystem collapse just wasn’t working as an explanation for these MSA declines, and these young scientists figured out what was really going on. For me, it’s a new way of understanding how pollution affects our atmosphere. The good news is that we are not seeing the collapse of marine ecosystems we thought we were. The bad news is that air pollution is causing this.”
The research not only sheds light on how pollution affects remote areas of the planet but also provides evidence that environmental regulations can help reverse the damage. The team found that, in Greenland, MSA levels began to recover in the 1990s as air quality regulations in Europe and North America took effect.
Osterberg expressed optimism about these findings, emphasizing that pollution reductions—particularly nitrogen oxide emissions – have a near-immediate effect. Unlike long-lived greenhouse gases like carbon dioxide, nitrogen oxides dissipate quickly once emissions are reduced.
“These data show the power of regulations to reduce air pollution,” Osterberg said. “I worry about younger people resigning to an environmental crisis because all we hear about is bad news. I think it’s important to acknowledge good news when we get it. Here, we see that regulations can work.”
While the study offers some hope, it also serves as a stark reminder of the global interconnectedness of pollution. The emissions from industrial activities in one part of the world can drastically affect atmospheric chemistry thousands of miles away. This reinforces the need for strong international cooperation on environmental policies to mitigate the impacts of air pollution, particularly in vulnerable regions like the Arctic.
Journal Reference:
Chalif, J.I., Jongebloed, U.A., Osterberg, E.C. et al. ‘Pollution drives multidecadal decline in subarctic methanesulfonic acid’, Nature Geoscience (2024). DOI: 10.1038/s41561-024-01543-w
Article Source:
Press Release/Material by Dartmouth College
Featured image: The Dartmouth-led study analyzed ice core data from Greenland and a 700-foot core members of the research team extracted from Denali National Park and Preserve in 2013. The Denali ice core contains a millennium of climate data in the form of gas bubbles, particulates, and compounds trapped in the ice. Credit: Mike Waszkiewicz
