Arctic sea ice decline

Arctic sea ice has been melting more each year, losing both its area and thickness since 1979. This change is mainly caused by global warming, which is linked to human activities that increase greenhouse gases in the atmosphere. Because of this warming, the Arctic is now warmer than it has been in thousands of years, and the time when the ice stays melted each year has grown longer.

The loss of sea ice is changing the Arctic and affecting weather patterns farther south. With less ice, some believe the jet stream may become weaker, leading to more extreme weather in places like mid-latitudes. The Arctic Ocean may also see more ships traveling through it, which can be dangerous for animals such as polar bears.

Scientists have measured this loss carefully. In September 2020, Arctic sea ice covered only 3.74 million square kilometers, its second-smallest size since records began. By 2026, the yearly maximum ice extent was also very low, showing how quickly the ice is disappearing. All of these changes remind us how important it is to care for our planet and understand the effects of climate change.

Definitions

In September 2012, the Arctic sea ice was at its smallest ever, covering 3,410,000 square kilometres. The Arctic Ocean is the area of water above latitude 65° N, and Arctic Sea Ice is the part of this ocean covered by ice.

The Arctic sea ice minimum is the day each year when the ice is smallest, usually in September after the summer melt. The Arctic sea ice maximum is when the ice is largest, usually in March after the cold season. Scientists measure sea ice extent, which is the area with at least 15% ice cover, to understand changes in the ice.

Arctic Ocean Arctic Sea Ice

Observations

Main article: Measurement of sea ice

The Arctic sea ice is getting smaller. This change is because the Earth is warming up. In summer, the ice melts more than it grows in winter.

Satellites show that Arctic sea ice is shrinking. The thick, old ice is disappearing. Big waves are also appearing where ice used to stay all year, which can break the ice apart.

Future ice loss

Arctic sea ice grows in the winter. On March 7, 2017, it reached its lowest maximum ever.

Older and thicker ice changes from 1984 to 2016 (video)

An "ice-free" Arctic Ocean, sometimes called a "blue ocean event" (BOE), means having less than 1 million square kilometers of sea ice. This is hard because the thick ice around the Canadian Arctic Archipelago is tough to melt.

It is hard to know exactly when the Arctic Ocean will become "ice-free". Some studies using different models say this could happen between the 2030s and 2050s. But there is a lot of uncertainty, and it is hard to know when it will happen.

Climate models

A 2006 paper said "near ice-free September conditions by 2040".

A 2009 paper estimated nearly ice-free Arctic Ocean around September 2037, maybe as early as 2028. In 2012, researchers found that under the highest-emission scenario, ice-free September could first happen between 14 and 36 years after 2007, with the median of 28 years (around 2035).

In 2009, a study using 18 climate models found they project ice-free Arctic a little before 2100 under a medium future greenhouse gas emissions scenario. In 2012, a different team found that while their mean estimate avoids ice-free Arctic before the end of the century, ice-free conditions in 2045 were within one standard deviation of the mean.

In 2013, a study projected ice-free September between 2054 and 2058 under a high emissions scenario. Under a moderate emissions scenario, Arctic ice gets very close to the ice-free threshold in 2060s, but does not cross it by the end of the century, and stays at an extent of 1.7 million km².

In 2014, IPCC Fifth Assessment Report indicated a risk of ice-free summer around 2050 under the scenario of highest possible emissions.

The Third U.S. National Climate Assessment (NCA), released May 6, 2014, reported that the Arctic Ocean is expected to be ice free in summer before mid-century. Models that best match historical trends project a nearly ice-free Arctic in the summer by the 2030s.

In 2021, the IPCC Sixth Assessment Report assessed that there is "high confidence" that the Arctic Ocean will likely become practically ice-free in September before the year 2050 under all SSP scenarios.^{: 1247–1251} 

A paper published in 2021 shows that the CMIP6 models project the first ice-free conditions around 2035 under a scenario of continually accelerating greenhouse gas emissions.

By weighting multiple CMIP6 projections, the first year of an ice-free Arctic is likely to occur during 2040–2072 under the SSP3-7.0 scenario.

Impacts on the physical environment

Global climate change

Main article: Ice–albedo feedback

See also: Climate change feedback

Arctic sea ice helps keep the polar regions cool. In summer, the bright ice reflects sunlight. When the ice melts, the dark ocean absorbs more sunlight and grows warmer. This warmth can cause more ice to melt, creating a cycle that makes things warmer over time.

Ice-free summer vs. ice-free winter

In 2021, a report said that Arctic summer ice will keep melting. Thinner ice lets more heat escape in winter, which can help the ice grow back if summers are cooler. But with more global warming, ice-free summers could happen more often. Very high warming might stop Arctic ice from forming in winter, but this is unlikely until temperatures rise a lot.

Amplified Arctic warming

Arctic warming is closely linked to sea ice loss. When sea ice disappears, the Arctic warms faster, especially during the months when ice normally melts. Antarctica, with its thick ice, has not warmed much in recent years.

Impacts on extreme weather

Barents Sea ice

The Barents Sea is warming quickly and may lose its ice permanently if global temperatures rise beyond 1.5 degrees Celsius. Changes in Barents Sea ice can affect weather in Europe and Asia, sometimes causing colder winters in some places and more rain in others. But these links are still being studied.

Other possible impacts on weather

Changes in sea ice near Greenland might affect weather patterns in Korea and India. Ice loss in other Arctic areas could influence spring temperatures in Russia.

Atmospheric chemistry

See also: Arctic methane release

As Arctic ice melts, it can release more methane—a gas that traps heat—into the atmosphere. Melting ice also allows mercury, a harmful substance, to enter ocean water and move up the food chain, affecting fish and animals that eat them.

Shipping

As Arctic ice melts, shipping routes across the Arctic Ocean have become more accessible. The number of voyages through the Arctic has increased, and some ships now cross without ice-breakers. This trend is expected to continue, which could change global trade routes and put pressure on the Arctic environment.

Impacts on wildlife

See also: Polar bear conservation § Climate change

The loss of Arctic sea ice changes the environment for many animals. It opens up new areas for people to reach, which can harm land animals and sea creatures.

Polar bears depend on sea ice to hunt seals. With the ice melting earlier and forming later each year, polar bears have less time to find their favorite food. They must look for other food on land, which is not as healthy. This change can make it harder for polar bears to grow and have babies, leading to fewer polar bears over time.

As the ice melts, tiny plants and animals under the ice can also change. Some small organisms may help the ice stay strong, while others might make it melt faster. Scientists are still studying how these changes affect the ice and the creatures that live there.