Whether scientists are looking back into the history of the Earth’s climate or making projections for its future, they must use simulations that rely on our understanding of how various factors interact with each other. Known as climate models, these simulations have become increasingly complicated as computers have become more powerful, sometimes revealing connections that leave scientists searching to explain.
Take wildfires in the Northern Hemisphere for example. Scientists have long known that the ash, soot and other particles these fires release into the atmosphere can travel to the Arctic. When these particles settle on Greenland’s ice sheet, they leave behind a record of their occurrence. Those particles also darken the surface, making it harder for the ice to reflect the sun’s energy, a problem that scientists have become increasingly alarmed about as the number of wildfires has increased. Now, new research, detailed in a paper published last month by Science Advances, a journal, seeming to show that there may be a connection between wildfires and sea ice, underscores that the mechanisms that drive the climate can be less straightforward than one would assume.
The findings are the result of a comparison of climate models carried out by scientists with the University of Colorado Boulder and America’s National Center for Atmospheric Research that found that particles from Northern Hemisphere wildfires that reach the Arctic affect the durability of sea ice. Although that is perhaps unsurprising given their effect on ice on land, the study also showed — in simulations at least — that the sea-ice melt this causes potentially has ripple effects on climate patterns elsewhere, reinforcing the interactions in a way that hasn’t been previously seen.
What the team found when comparing the factors that are used to create a climate model (things like carbon-dioxide or methane emissions or solar radiation) between the new and previous generation of climate models was that — again, according the simulated reality of the climate model — particles from wildfires were the biggest driver of Arctic sea-ice loss.
The reason why these particles play such a big role, it appears, is the way they interact with clouds above the Arctic. During years in which there are more wildfires (and consequently more particles released), more and thicker clouds tend to be observed. During years when there are fewer fires, fewer and thinner clouds are observed. This, though, allows more solar radiation to get through and melt more ice. Previous research had already shown a link between sea-ice melt and the number of large wildfires in the western US, but, by showing that smoke from wildfires can help protect the ice, the research suggests that the relationship is complicated.
“When we think about climate, everything’s really interconnected, and this is really a great example of that,” said Alexandra Jahn, an associate professor in atmospheric and oceanic sciences and the University of Colorado Boulder and one of the authors of the paper. “When we’re thinking about climate processes, it’s really a global problem, and we can’t study it in any isolated fashion. We really always have to look at the global picture to understand all these different interactions.”
Although the research only looked at one specific climate model (known as CESM2), the scientists involved believe the work provides the basis for future studies. “The goal that we’re trying to achieve here is to have these climate simulations be more reliable and give us projections that can then inform policy makers and societal choices,” Patricia DeRepentigny, a post-doctoral fellow at the National Center for Atmospheric Research and the lead author of the paper, said.
Kevin McGwin, Polar Journal
Featured image: Peter Griffith / Nasa
Patricia DeRepentigny, Alexandra Jahn, Marika M. Holland, Jennifer E. Kay, John Fasullo, Jean-François Lamarque, Simone Tilmes, Cécile Hannay, Michael J. Mills, David A. Bailey, Andrew P. Barrett. Enhanced simulated early 21st century Arctic sea ice loss due to CMIP6 biomass burning emissions. Science Advances, 2022; 8 (30) DOI: 10.1126/sciadv.abo2405
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