Â鶹ÒùÔº

Climate change is starving the Arctic Ocean of essential nutrients, with the region's six largest rivers now delivering far less of the type of nitrogen that marine ecosystems need to survive, according to new research in one of Earth's most vulnerable regions.

The study, led by Bridger J. Ruyle of NYU Tandon School of Engineering, is published in , where it has been selected as an Editor's Choice. Ruyle completed the research as a Postdoctoral Fellow at the Carnegie Institution for Science.

The study found that warming temperatures and thawing permafrost are fundamentally altering the chemistry of Arctic rivers. The result is that coastal food webs that have sustained Indigenous communities for millennia are being deprived of inorganic nitrogen, an essential nutrient, potentially triggering cascading effects throughout the Arctic Ocean ecosystem.

"This is a red flag for the Arctic," said Ruyle, who joined NYU Tandon in the summer of 2025 as an Assistant Professor in the Civil and Urban Engineering Department. "Rapid changes in river nitrogen chemistry could completely transform how these marine ecosystems function."

The research analyzed 20 years of data from six major Arctic rivers—the Yenisey, Lena, Ob', Mackenzie, Yukon, and Kolyma—which collectively drain two-thirds of the land area flowing into the Arctic Ocean. These rivers transport nitrogen that supports up to 66% of the ecosystem's primary production in coastal Arctic regions.

Between 2003 and 2023, Ruyle and colleagues documented declines in inorganic nitrogen accompanied by simultaneous increases in dissolved organic nitrogen, a far less bioavailable form of the element, in four of the six rivers. The findings reveal that warmer temperatures and increased precipitation caused by climate change are driving the shift in nitrogen composition through their effects on river discharge and permafrost thaw.

Using sophisticated statistical modeling, the researchers identified permafrost loss as the key factor explaining the diverging trends between organic and inorganic nitrogen in these rivers. The study combined 20 years of water chemistry data with environmental variables including temperature, precipitation, land cover, and permafrost extent to pinpoint the climate drivers behind the chemical shifts.

This Arctic rivers research represents Ruyle's broader research mission to understand how human activity, climate change, and natural processes interact to affect water quality globally. Among other areas of focus, his work includes tracking "forever chemicals" and pharmaceuticals in wastewater.

"Whether we're looking at PFAS contamination in drinking water or nitrogen cycling in Arctic rivers, the common thread is understanding how environmental changes propagate through water systems," Ruyle explained.

His research explores how human activity, the biosphere, and climate change affect water quality, with particular focus on developing analytical tools to quantify chemical contamination and developing models using remote sensing data to assess climate impacts.

The Arctic findings have implications for ecosystem management and climate adaptation strategies. River transport of nitrogen is estimated to support up to 66% of primary production in Arctic coastal regions, making these compositional changes important for marine food webs and the Indigenous communities that depend on these resources.

The research also highlights the interconnected nature of global environmental challenges. As Ruyle noted in previous work on pharmaceutical contamination, climate-driven water scarcity could exacerbate water quality problems, as there's less dilution of contaminants during drought conditions. The Arctic study similarly shows how temperature and precipitation changes cascade through complex biogeochemical systems, resulting in water quality and ecosystem impacts.

"This work demonstrates why we need to think about water quality and climate change as fundamentally linked challenges," Ruyle said. "As climate change intensifies, we must understand these interconnections to protect both human health and ecosystem integrity."