While the loss of Arctic sea ice remains an unfolding climate disaster, new research suggests that melting ice may deliver an unexpected boost to carbon-eating algae—organisms that could help absorb surprising amounts of greenhouse gas.
The paradox of a worsening climate event that might also enhance Earth’s natural ability to offset carbon emissions is not lost on scientists, who caution that how this process will ultimately unfold is still uncertain.
In a new study published in Communications Earth & Environment, researchers identify a key factor behind this potential shift: a dramatic increase in nitrogen ammonia in the Arctic Ocean expected due to continued sea ice melt, which is the primary food for algae.
Nitrogen Fixation
At the heart of the discovery is the team’s detection of nitrogen fixation occurring beneath the central Arctic Ocean’s sea ice for the first time. Through this process, bacteria convert atmospheric dinitrogen gas into ammonia—a form of nitrogen that most marine organisms can readily use. Because most life forms cannot absorb dinitrogen gas directly, ammonia serves as an essential building block in the Arctic food web, supporting not only bacteria but also algae and other marine life.
“Until now, it was believed that nitrogen fixation could not take place under the sea ice because conditions were thought to be too harsh for the organisms that perform it,” said lead author Lisa W. von Friesen.
“We were wrong.”
While nitrogen fixation occurs throughout much of the world’s oceans, its Arctic form is unusual. Instead of being carried out by cyanobacteria—as is typical elsewhere—it is performed by non-cyanobacterial microbes, marking a distinct ecological adaptation to extreme polar conditions.
The Edges of the Arctic Sea Ice
Researchers observed the highest rates of nitrogen fixation along the edges of melting sea ice, where conditions are most dynamic. Although fixation also occurs beneath the remaining ice, it happens at a much slower rate. From these findings, the team concluded that as sea ice continues to retreat, nitrogen availability in the Arctic Ocean will increase dramatically—a factor not currently accounted for in most climate models.
“In other words, the amount of available nitrogen in the Arctic Ocean has likely been underestimated, both today and for future projections. This could mean that the potential for algae production has also been underestimated as climate change continues to reduce the sea ice cover,” said von Friesen.
“Because algae are the primary food source for small animals such as planktonic crustaceans, which in turn are eaten by small fish, more algae can end up affecting the entire food chain,” she added.
Rethinking Climate Models
An increased supply of nitrogen could effectively fertilize the Arctic Ocean, allowing algae to thrive. A rapidly expanding algal population would represent an ironic twist—a climate-driven change that might help mitigate climate change itself by drawing down atmospheric CO₂ as algae grow and store carbon in their biomass.
“For the climate and the environment, this is likely good news. If algae production increases, the Arctic Ocean will absorb more CO2 because more CO2 will be bound in algae biomass,” said co-author Lasse Riemann. “But biological systems are very complex, so it is hard to make firm predictions, because other mechanisms may pull in the opposite direction.”
While many variables remain to be studied, the researchers emphasize that the discovery is too significant to ignore. Future Arctic climate models, they argue, must incorporate this newly identified process to more accurately forecast ecological and atmospheric outcomes.
“We do not yet know whether the net effect will be beneficial for the climate,” Rieman concluded. “But it is clear that we should include an important process such as nitrogen fixation in the equation when we try to predict what will happen to the Arctic Ocean in the coming decades as sea ice declines.”
The paper, “Nitrogen Fixation Under Declining Arctic Sea Ice,” appeared in Communications Earth & Environment on October 20, 2025.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.