(AFP) - The worrying shrinkage of Arctic sea ice could accelerate dramatically in coming decades, leaving the planet's most northerly ocean virtually devoid of ice in summer by 2040, according to a new study.
The paper, which appeared in the US journal Geophysical Research Letters on Tuesday, mainly points the finger at greenhouse-gas emissions, reports Trend.
It warned that if carbon pollution continues to increase at present rates, the Arctic's normal cycle of freezing and thawing faces catastrophic disruption.
A simulation run by scientists at the National Center for Atmospheric Research (NCAR) and Canada's McGill University predicted that the area covered by ice in September -- before new ice begins to form each year -- could shrink from about 5.9 million square kilometres to 1.9 million sq. kms. (2.3 million to 770,000 sq. miles) within a decade.
By 2040, "only a small amount of perennial sea ice" would remain along the north coasts of Greenland and Canada in summer, NCAR said in a press release.
In winter, ice thickness would be reduced from about 3.5 metres (about 12 feet) to less than a metre (three feet).
"We have already witnessed major losses in sea ice, but our research suggests that the decrease over the next few decades could be far more dramatic than anything that has happened so far," said NCAR scientist and lead author of the study, Marika Holland. Greenhouse gases trap the Sun's heat, gradually forcing up Earth's surface temperature.
But several peripheral factors could also account for such a rapid meltdown.
Open water absorbs more sunlight than ice, accelerating the rate of warming and leading to more ice loss. In addition, global climate change is likely to drive warmer ocean currents into the Arctic region.
"This is a positive feedback loop with dramatic implications for the entire Arctic region," Holland said.
The shrinkage of the Arctic ice cap is viewed with alarm by scientists, as it appears to perturb important ocean currents elsewhere, notably the Gulf Stream, which gives western Europe its balmy climate.
It also threatens animals such as polar bears and seals that depend on ice -- as well as Inuits and other native peoples who hunt these animals and have to travel on thinner ice in this quest.
There are geopolitical implications, too, as Canada, Russia and the United States jockey to claim rights over transpolar passages that open up within their newly ice-free waters.
In September, European scientists unveiled satellite images from late August showing that perennial sea ice -- thick ice that is normally present year-round and is not affected by the Arctic summer -- had disappeared over an area bigger than the British Isles.
The study released Tuesday concludes that reduced rates of greenhouse gas emissions could slow the ice loss. "Our research indicates that society can still minimize the impacts on Artic ice," Holland said.