As soon as 2027, the Arctic could see its first summer in which nearly all sea ice melts — an unsettling milestone for the planet. An international team of researchers, including climatologist Alexandra Jahn of the University of Colorado, Boulder, and Céline Heuzé of the University of Gothenburg, Sweden, used computer models for the first time to predict when the northernmost ocean will see its first ice-free day. An ice-free Arctic would change weather patterns, with major consequences for ecosystems and the Earth's climate.
"The first ice-free day in the Arctic will not change the situation dramatically," said Jenn, an associate professor in the Department of Atmospheric and Ocean Sciences and a researcher at the Arctic and Alpine Institute at the University of Colorado Boulder. "But it will show that through greenhouse gas emissions, we have fundamentally changed a defining feature of the Arctic Ocean's natural environment, which is that the Arctic Ocean is covered with sea ice and snow year-round."
These research results were recently published in the journal Nature Communications. Jahn will also present the research results on December 9 at the annual meeting of the American Geophysical Union in Washington, DC.
As the climate warms due to increased greenhouse gas emissions, Arctic sea ice is disappearing at an unprecedented rate, at a rate of more than 12% per decade.
In September this year, the National Snow and Ice Data Center reported that this year’s Arctic sea ice nadir (the day with the least frozen water in the Arctic) was one of the lowest recorded since 1978.
This year's minimum coverage area is 1.65 million square miles (or 4.28 million square kilometers), which is higher than the all-time low observed in September 2012. However, compared with the average coverage area of 6.85 million square kilometers from 1979 to 1992, there is still a significant decrease.
When the ice area of the Arctic Ocean is less than 1 million square kilometers, scientists call the Arctic an ice-free area. Previous forecasts of Arctic sea ice changes have focused on predicting when the ocean will be ice-free for a full month. Jenn's previous research has shown that the first ice-free moon is almost inevitable and may occur in the 2030s.
As the tipping point approaches, Jahn wonders when the first summer of melting nearly all Arctic sea ice will occur.
"Because the first ice-free day is likely to precede the first ice-free month, we need to be prepared. It is also important to understand what events could cause all sea ice in the Arctic Ocean to melt," Heuzé said.
Jahn and Heuzé used the results of more than 300 computer simulations to predict/estimate the first ice-free day in the Arctic. They found that most models predict that the first ice-free day could occur within nine to 20 years after 2023, regardless of how humans alter greenhouse gas emissions. The earliest ice-free day in the Arctic Ocean could occur within three years.
This is an extreme scenario, but based on the model it is possible. A total of nine simulations suggested that ice-free days could occur within three to six years.
The researchers found that a series of extreme weather events could melt 2 million square kilometers or more of sea ice in a short period of time: an unusually warm autumn first weakens sea ice, followed by warm Arctic winters and springs that hinder sea ice formation. When the Arctic experiences this extreme warming for three or more years in a row, the first ice-free day is likely to occur in late summer.
Warmer years like this have already occurred. For example, in March 2022, temperatures in the Arctic were 50 degrees Fahrenheit above average, and the area around the Arctic was almost melting. Heuzé said the frequency and intensity of these weather events will only increase as climate changes.
Sea ice protects the Arctic from the effects of climate warming by reflecting incoming sunlight back into space. With less reflective ice, the darker water will absorb more heat from the sun, further raising temperatures in the Arctic and globally. Additionally, a warming Arctic could alter wind and ocean current patterns, leading to an increase in extreme weather events around the world.
But there's good news: According to the study, significant reductions in emissions could delay the time when the Arctic becomes ice-free and shorten the time the oceans remain ice-free. Any measures to reduce emissions will help protect sea ice.
Compiled from /ScitechDaily
DOI:10.1038/s41467-024-54508-3