Arctic: Why the ice is melting and CO₂ emissions are rising

The Arctic, once a stable store of organic carbon, is now releasing more carbon dioxide (CO₂) than it absorbs. According to the latest NOAA Arctic Report Card 2024, thawing permafrost, increased microbial activity, and more frequent wildfires are chiefly responsible for this development. The Arctic, which long acted as a carbon sink, is now releasing greenhouse gases at an accelerating rate. This trend amplifies global warming and threatens Arctic ecosystems and the animal species that live there.

When permafrost thaws: carbon release with global consequences

Permafrost soils, which store more than half of the world’s organic soil carbon, are thawing as temperatures rise. Much like a freezer in which thawed food spoils quickly, thawing permafrost sets microbial processes in motion that decompose stored organic matter and release large amounts of carbon dioxide (CO₂) and methane.

In addition, tundra fires north of the Arctic Circle and fires in the boreal forests near the Arctic contribute substantially to carbon dioxide releases. According to the NOAA Arctic Report Card 2024, fires in the high Arctic alone released 42.3 million tonnes of CO₂ in 2024 – the second-highest level since measurements began.

Another decisive factor is the rapid rise in sea temperatures. A study by Merchant et al. (2024) shows that ocean surface temperatures are increasing not linearly but at an accelerating rate. While the warming trend between 1985 and 1989 was still 0.06 degrees Celsius per decade, it had already risen to 0.27 degrees Celsius per decade between 2019 and 2023. This has serious implications for ocean currents and weather patterns, which in turn influence permafrost and ice formation in the Arctic.

Impacts on wildlife

Rapid warming is already having noticeable effects on Arctic wildlife. A prominent example is migratory caribou (Rangifer tarandus), whose populations have declined by 65 percent over the last two to three decades. The habitat of these animals is changing dramatically: as the tundra greens, taller shrubs displace the lichens that are vital to caribou, making it harder for them to find food.

Arctic seal species such as the ringed seal (Pusa hispida) are also adapting to these changes by increasingly consuming saffron cod (Eleginus gracilis) instead of the more energy-rich Arctic cod (Arctogadus glacialis). However, the long-term consequences of this dietary shift are still uncertain.

One of the most threatened species is the polar bear (Ursus maritimus). Especially in Hudson Bay, populations risk regional extinction as early as the 2030s if climate change continues unchecked. Scientists predict that warming of more than two degrees Celsius could lengthen ice-free periods so much that polar bears can no longer find sufficient food and could go extinct in the 2030s.

Greenhouse gases: why methane and carbon dioxide are so harmful

Methane (CH₄) and carbon dioxide (CO₂) are two of the most significant greenhouse gases contributing to global warming. While CO₂ remains in the atmosphere for centuries and drives long-term climate change, methane is even more dangerous in the short term: over a period of 20 years, it has an approximately 80 times stronger warming effect than CO₂.

Methane is produced mainly by the breakdown of organic matter in thawing permafrost as well as by human activities such as livestock farming and fossil fuel extraction. Although it breaks down in the atmosphere within about twelve years, its high greenhouse effect accelerates warming. This, in turn, intensifies permafrost thaw and releases even more methane – a dangerous feedback loop that further destabilizes the climate.

Global consequences and the need for action

The Arctic influences the entire climate system through its role as a global cooling system. The loss of sea ice reduces the reflection of sunlight and promotes further warming. In addition, atmospheric circulation changes, which can lead to more extreme weather events worldwide.

In particular, the accelerated warming of the oceans contributes to destabilizing the Arctic. The study by Merchant et al. shows that almost half of the recent temperature increase is attributable to human-caused climate change. This development boosts greenhouse gas releases in the Arctic, creating a dangerous feedback effect.

The NOAA Arctic Report Card 2024 emphasizes that addressing these challenges requires close cooperation between scientists and Indigenous communities. Indigenous peoples have centuries of experience dealing with climatic changes and can provide valuable insights for adaptation. At the same time, far-reaching measures to reduce greenhouse gas emissions are necessary to stabilize an overheated planet.

A look at Europe: potential for carbon storage

While the Arctic is increasingly becoming a source of carbon dioxide and methane, a new report by BirdLife Europe highlights the immense potential of European ecosystems to store carbon. According to the report, fully restored natural ecosystems in the EU could store around 13 billion tonnes of carbon – equivalent to global annual CO₂ emissions. Forests, peatlands, and wetlands in particular could bind substantial amounts of CO₂ through targeted restoration measures, helping to combat climate change. Expanded restoration could help mitigate some of the negative feedback effects triggered by Arctic warming and significantly improve Europe’s net carbon balance.

The Arctic is undergoing an ongoing, rapid transformation with far-reaching global consequences. Without decisive action, we risk irreversible changes to the climate system.

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Sources

• Moon, Twila A. et al. (2024). NOAA Arctic Report Card 2024: Executive Summary.
• Merchant, C. et al. (2025). Accelerated Ocean Surface Warming, Environmental Research Letters.
• BirdLife Europe (2025). Carbon Sequestration on Land through Nature-Based Solutions and Land-Use Trade-Offs.