Recent news stories have focused on the slowdown in the decline of Arctic sea ice and some have interpreted these as ‘good news stories’, but what does the science really show?

As sea ice is a vital aspect of the delicate and complex Earth system, it’s vital we understand exactly what is happening with sea ice as global temperatures continue to rise.

Sea ice should not be confused with icebergs, which break away from glaciers as they reach the ocean.

Sea ice forms when sea water freezes, creating ice floes that float on the surface. Sea ice is found year-round in the Arctic and Southern oceans, where the air is cold enough to freeze salt water.

Unlike land-based ice, when sea ice melts it does not contribute to sea level rise in a significant way, but it still has an impact on the Earth’s systems.

Sea ice helps regulate the Earth’s temperature

Sea ice has a higher ‘albedo’ than the surrounding sea water. This means it is more reflective due to its lighter colour. It reflects solar radiation from the sun back into space helping to keep the planet cool and regulating global temperatures.

When sea ice melts, there is a larger proportion of darker sea surface with a ‘low albedo’, absorbing more of the sun’s heat. This creates a feedback loop which means the planet warms further.

This process creates a ‘positive feedback mechanism’. This refers to changes in a system which creates effects that make that change even stronger. As melted ice exposes more dark ocean water, which absorbs more heat from the sun than ice does, the extra heat causes even more ice to melt, which exposes more dark water, and so on. The process reinforces itself and speeds up.

Sea ice helps drive ocean circulation patterns

Ocean currents, which determine weather patterns around the world and help drive the Earth’s wider carbon cycle, are driven by differences in temperature and salinity of the water. This is referred to as thermohaline circulation.

A complex series of processes take place during the sea ice life cycle. Sea water contains salt, making it more dense than fresh water. When it freezes, the ice crystals can’t retain all the salt and so some is rejected into the water around it, making it denser. When sea ice melts, it releases freshwater into the ocean. These fluxes in salt and freshwater dictate the movement of water within the polar oceans and have implications for wider ocean circulation.

One circulation pattern which is sensitive to declining Arctic sea ice is the Atlantic Meridional Overturning Circulation (AMOC), a system of ocean currents that includes the gulf stream. The gulf stream relies on cold salty water sinking in the North Atlantic to drives the flow of waters from the Azores up towards northern Europe.

As sea ice in the Arctic melts, the water in the northern Atlantic Sea is becoming increasingly diluted and therefore not as heavy. This change has the potential to divert or even collapse these currents and change the patterns of weather Europe and northern United States have become used to, such as milder winters and warmer summers.

Sea ice is a habitat for some of the Earth’s most beautiful species

Sea ice also provides a habitat for a range of species including polar bears, whales, krill and seals. As it melts, these species are increasingly under pressure.

Key indicators of sea ice health

Scientists monitor sea ice using:

• Extent: The surface area of the sea where the ice is at least 15% ice concentration.
• Thickness: The vertical depth of the ice
• Ice volume: The actual amount of ice in volume.

Observing changes in these indicators helps scientists gain a robust understanding of climate change.

How headlines can misrepresent the science

There have been some viral social media stories suggesting that sea ice hasn’t changed over the decades and that sea ice decline is a myth.

There have been other stories that focus on how sea ice in the Artic is not declining at the rate we would expect considering the Arctic is warming four times faster than the rest of the planet.

These could seem like good news stories.

What the science reveals

• CPOM data show average Arctic sea ice thickness in October has reduced by 0.6 centimetres per year since 2010 suggesting an overall decline in sea ice volume even if extent has not reduced.
• Arctic sea ice has declined in both extent and volume throughout the year, with the most significant losses occurring in late summer, according to ESA satellite data.
• In this article, NASA reported that in 2025 global sea ice coverage was at a record low. This is due to a rapid decline in Antarctic sea ice extent. There is more information about the current state of sea ice cover in this report from NASA.

Explaining a complex system in one sentence

The problem with headlines is that you can’t capture a complex situation in one sentence, and sea ice is a dynamic and expansive puzzle.

• Some headlines focus on sea ice extent, which is only one indicator of sea ice coverage, ignoring thickness and volume. Even if the extent of the sea ice remains the same from one year to the next, if it is only half as thick, then the total volume of ice has also halved. The Arctic is losing its thickest multi-year ice, with the ice pack becoming increasingly seasonal. This means that overall there is less sea ice, and therefore more freshwater in the ocean. 
• Decline in sea ice may appear to slow down due to ‘seasonal variability’, which are ‘short-term variations’ while the overarching long-term trend, monitored over many decades, may still be one of decline. Scientists use climate model simulations to help understand and predict the behaviour of sea ice. Models show that as Arctic sea ice declines over multiple decades, we can expect periods of no change or even growth, due to natural variability within the climate system.
• As Julienne Stroeve points out in this article, even though sea ice melts during the summer, new ice forms again in winter when temperatures drop. A growth that can obfuscate some of the ice lost in summer. As winters get shorter, there will be less time for the ice to grow, and it won’t grow as thick meaning this “buffer” replacing lost ice is reducing.

The bigger picture

When media outlets report on scientific studies relating to changes in the cryosphere, the focus might be on one element. The problem with this is it might paint a picture of the state of Earth’s ice that may not reveal the full story.

Anthropogenic Global Warming (AGW), long-term warming of the Earth’s climate due to human activities such as burning fossil fuels, is undeniably taking place. The WMO recently declared 2024 as the hottest year on record, and you can see a graph showing global temperatures since 1860 to see how temperatures have, and are rising over centuries.

The Earth’s ice still sees natural cyclical changes caused by ocean currents, short-term weather patterns and atmospheric conditions. This means sea ice extent may recover in the winters, but the long-term trend due to warming remains true.

Over the last three decades sea ice in the Arctic has declined during the summer months and winter ice is newer and thinner. Despite seasonal ups and downs, the net loss of ice is accelerating.

These trends are worrying, but there are some positives we can focus on.

Although the challenge is great, the world is equipped to tackle that challenge.

Monitoring sea ice is rapidly improving, and scientists are getting increasingly better at understanding these huge and dynamic areas of ice. This means we can better project future outcomes and plan and mitigate for future changes.

The fact that sea ice still shows seasonal recovery during winters means there is still the opportunity to protect it through working towards net zero and limiting global warming.

With increasingly sophisticated satellite missions and models, multi-agency projects and powerful movements pressing for change, we can adapt and protect our changing planet.

Featured image credit: Amy Swiggs