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 at least 4,000 years, and the time when the ice stays melted each year has grown longer.

The loss of sea ice is not only changing the Arctic but also 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

On September 2, 2012, the Arctic sea ice reached its smallest size 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 often measure sea ice extent, which is the area with at least 15% ice cover, to better understand changes in the ice.

Arctic Ocean Arctic Sea Ice

Observations

Main article: Measurement of sea ice

The area covered by sea ice in the Arctic has been getting smaller over the past few decades. This change is linked to climate change, which causes the Earth to warm up. During summer, the ice melts more than it refreezes in winter.

Satellites have shown that the amount of Arctic sea ice, both in area and thickness, has been decreasing for many years. Older, thicker ice has become much less common. Scientists have also noticed big waves in areas where ice used to be year-round, which can further break up the ice.

Future ice loss

Arctic sea ice grows and extends through the winter. On March 7, 2017, Arctic sea ice reached its record lowest maximum.

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

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

Estimating the exact year when the Arctic Ocean will become "ice-free" is very difficult. Some studies using different models predict this could happen between the 2030s and 2050s. However, there is a lot of uncertainty, and it is hard to know exactly when it will happen.

Climate models

A 2006 paper examined projections and predicted "near ice-free September conditions by 2040".

A 2009 paper applied observational constraints to projections and estimated nearly ice-free Arctic Ocean around September 2037, with a chance it could happen as early as 2028. In 2012, this pair of researchers found that under the highest-emission scenario, ice-free September first occurs between 14 and 36 years after the baseline year of 2007, with the median of 28 years (i.e. around 2035).

In 2009, a study using 18 climate models found that they project ice-free Arctic a little before 2100 under a scenario of medium future greenhouse gas emissions. 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 compared projections and found good agreement. Altogether, it projected ice-free September between 2054 and 2058 under a high emissions scenario, while 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. During summer, the bright surface of the ice reflects sunlight. When the ice melts, the dark ocean absorbs more sunlight, which makes the ocean warmer. This warmth can cause more ice to melt, creating a cycle that worsens over time. Between 1979 and 2011, Arctic ice loss had an impact on climate similar to a quarter of all carbon dioxide emissions during that period. This is a major factor in global warming.

Ice-free summer vs. ice-free winter

In 2021, a report said that Arctic summer ice will continue to melt without reaching a point of no return. Thinner ice lets more heat escape in winter, which can help the ice recover if summers are cooler. However, with more global warming, ice-free summers could happen more often and earlier. Very high warming could eventually stop Arctic ice from forming in winter, though this is unlikely to happen until temperatures rise much higher than today.

Amplified Arctic warming

Arctic warming is linked closely to sea ice loss. When sea ice disappears, the Arctic warms faster, especially during months when ice is normally melting. In contrast, Antarctica has thick ice that keeps it stable and has not warmed much in recent decades.

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. Research suggests that changes in Barents Sea ice can affect weather in Europe and Asia, sometimes leading to colder winters in some areas and more rain in others. However, 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. In some areas, there are only about 900 polar bears left.

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.