The Arctic Ocean May Have Passed a Crucial Tipping Point That Could Harm Food Webs and Worsen Climate Change

Sea ice loss seems to have triggered a decline in the nutrient nitrate, affecting the tiny organisms that form the foundations of marine food chains and absorb atmospheric carbon dioxide, according to a new study

Sara Hashemi | Daily Correspondent

July 8, 2026 11:36 a.m.

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The Arctic Ocean is losing sea ice at an unprecedented rate, mainly because of human-caused climate change. While the amount rises and falls with the seasons, satellite images have shown that over recent decades, increasingly more ice has been melting in the summers and less has been forming in the winters.  

Now, scientists say that the decline in frozen water has crossed a critical tipping point, and that the shift could have devastating consequences for wildlife and the ocean’s ability to stabilize Earth’s climate.

A study published in the journal Communications Earth & Environment on May 28 found that melting ice has drastically reduced levels of nitrate, a key nutrient in the ocean. The change, which the research team suspects is irreversible, might mean that in the future, the Arctic Ocean will only be able to support phytoplankton—plant-like microorganisms—that are smaller and less nutritious than their larger counterparts that play a big role in the foundations of marine food webs.

“For years, sea-ice loss in the Arctic Ocean was expected to increase phytoplankton growth because more sunlight could reach surface waters,” says study co-author Marta Santos-García, a marine biogeochemist at the University of Edinburgh in Scotland, in a statement.

However, she and her colleagues found that the relationship has changed. To do so, the team examined ocean sampling data collected from 1998 to 2023 in the Fram Strait, a passage between Greenland and the Norwegian archipelago Svalbard where the Arctic and Atlantic oceans meet. Past research has revealed that sea ice there has become thinner in recent years, so the scientists wanted to know how that might affect interactions between biology, chemistry and geology.

Their analysis suggests that nitrate levels passed a tipping point around 2009. The nutrient has been steadily declining in the Fram Strait since then—a time frame that coincides with a dramatic drop in sea ice.

The shrinking sea ice probably boosted a process called benthic denitrification, according to the researchers. Large swaths of the region are now exposed to sunlight, allowing photosynthetic phytoplankton to thrive. When the microorganisms die, they sink to the seafloor, where they are decomposed by bacteria and archaea. Eventually, they consume all the nitrate, meaning waters that flow to the Fram Strait and other areas have little of the nutrient, allowing tinier, more nitrate-efficient phytoplankton—called microplankton—to take over.   

“Shifts towards smaller phytoplankton have already been observed in parts of the Arctic, although these changes have not previously been linked to nitrate losses,” Santos-García tells Sascha Pare at Live Science. Microplankton are generally not great at moving energy up the food web, she adds, leading to less food for larger types of plankton, fish, seabirds and marine mammals.

Earth’s climate could also be affected. Phytoplankton need nitrates for photosynthesis, in which they remove heat-trapping carbon dioxide from the atmosphere, so the shift might reduce the ocean’s ability to store carbon. That would be a big loss. The ocean has absorbed about 30 percent of human-emitted carbon dioxide between 1994 and 2004, according to a study published in 2019.   

The new work reveals that the Arctic Ocean has moved from being a system that is mainly limited by sunlight to one that is mainly limited by nitrate, says Jean-Éric Tremblay, a biologist at Laval University in Canada who was not involved in the research, to Alec Luhn at New Scientist.

“What this is showing is that the Arctic Ocean is not going to become the oasis of the future,” he adds. “If you increase [phytoplankton] production, you enhance denitrification, you remove nitrate, and further down the line you reduce productivity.”

Unfortunately, the researchers think denitrification has passed a point of no return.

“Even if sea ice were to increase temporarily, the Arctic nutrient system responds over much longer timescales,” Santos-García tells Live Science. “Short-term increases in sea ice would be unlikely to rapidly reverse the decline in nitrate inventories, which may take much longer to recover.”

Sara Hashemi | Read More

Sara Hashemi is a science writer and fact-checker currently based in New York City. Her work has appeared in Sierra, The Body, Maisonneuve magazine and more.