Somewhere along the northern coast of Siberia coast in the mid-1990s, Russian researchers and their international colleagues cruised through vast estuaries — where fresh and saltwater mix — on a giant icebreaker ship. Pausing along the Yenisei and Ob’ Rivers, they slipped tea-like water into test tubes — the first steps in a decades-long research project to study how Arctic river systems are changing over time.

NASA estimates this is the planet’s warmest record in 10 years, accelerated by anthropogenic sources such as the release of key greenhouse gases since the Industrial Revolution. A spike in temperature this drastic has led to a myriad of consequences, including extreme weather events, widespread ecological damage and declining biodiversity.

But what is most worrying to scientists? Arctic permafrost.

Surface temperature in the Arctic region has increased three to four times more than the global average, clocking in at 3 degrees Celsius.

“In the Arctic, climate change is not a political opinion — it’s scientific reality,” Texas A&M Professor of Marine & Coastal Environmental Science Rainer Amon, Ph.D., said. “There is a large amount of organic carbon locked up in the North’s Arctic permafrost. It’s almost twice the amount of what’s currently found in atmospheric CO2. The annual loss of permafrost will have substantial effects on river chemistry and CO2 concentrations in the atmosphere.”

Amon said that human activity has pushed the planet to a threshold of no return and that Earth’s system itself might become a carbon source rather than a sink, with thawing permafrost naturally fueling rising temperatures globally. To study the effects of a melting Arctic, Amon and an international team of scientists looked to the Arctic’s largest rivers.

In a 2023 study, the team reported on 17 years of seasonal samples from six major Arctic river systems. The data stems from the Arctic Great Rivers Observatory, or ArcticGRO, a large collection project that is still active today but is now, for political reasons, limited to North American rivers. 

One of the project’s goals is to analyze river outflows that serve as “fingerprints,” tracing Earth’s changes in geography and chemical signature over time.

“Two decades after first embarking on the Arctic Great Rivers endeavor, we are finding changes across the land-ocean Arctic system that far surpass the 9.5% increase in atmospheric CO2 measured over the period of our dataset,” lead author and University of Alberta professor Suzanne Tank, Ph.D., said in a Frontiers news release.

Alkalinity — the ability of water to neutralize acids like calcium — increased by 18%. This uptick influences the amount of CO2 released from rivers into the atmosphere. Nitrate — an important nutrient for plants — decreased by 32%. This means there are fewer nutrients available to aquatic ecosystems, negatively impacting food webs in the rivers and nearby coastal areas.

But what surprised ArcticGRO researchers was that dissolved organic carbon — the carbon stored in permafrost that has now melted into river water — showed no change despite a huge loss of ice and a drastic increase in Arctic surface temperatures.

“The Arctic is changing very fast,” co-author and senior scientist at the University of Chicago’s Marine Biological Laboratory James McClelland, Ph.D., said. “These results bring more questions to the table: How does this organic matter decompose? Where? How does it influence the coastal ecosystems it’s decomposing in?” 

Amon theorizes the dissolved organic carbon is being respired by microbes early on.

Microbes are similar to little invisible bugs that live inside both the soil and water of Arctic rivers. They “eat” dissolved organic carbon for energy and breathe it out as carbon dioxide, just like humans. This means that thawing permafrost releases carbon directly into the atmosphere, bypassing the river system and Arctic Ocean altogether.

“This is why it is important to go upstream, close to where the permafrost is melting — that’s where the action is happening,” Amon said. “But the reality is that there are many barriers to getting that data: geopolitics, remote locations, international collaboration and the big one, funding.”

Operating an icebreaker, a ship built to plow through frozen seas, can cost more than $100,000 a day, plus nearly $1 million in diesel fuel. Germany’s next-generation icebreaker, slated for completion in 2030, carries a price tag of over $1 billion. Few financial backers can provide that level of support, making the search for grants especially challenging.

Despite these challenges, McClelland stresses the importance of this research as global temperatures continue to rise.

“What happens in the Arctic does not stay in the Arctic,” McClelland said. “When permafrost thaws at high latitudes, CO2 is released to the atmosphere and affects the global climate. It’s not just some far-off place where maybe things are changing fast. Those things don’t just matter to the organisms and people living up there — they matter to all of us. It has implications for how global ocean circulation works. That’s why it’s so important that we continue to study these trends.”

Amon’s work to maintain monthly river collections with colleagues in Siberia ended in 2022 amid political tensions, so he is now recruiting graduate students to help analyze those samples. But access to the rivers’ source points — the ultimate goal — may stay out of reach for now.  

“What people should take away from this study is that things are moving, they are changing,” Amon said. “Yes, they have always changed, but they have never changed as fast as they are now. We need to get a handle on it.”