First ice-free summer day forecast for Arctic Ocean by 2030s

Under a worst-case scenario, Arctic could become ice-free for three quarters of the year, including some winter months

Svalbard, Norway. Frozen ocean water in the Arctic shrinks during summer as it gets warmer, then forms again in the long winter. AP

Sea ice could disappear during some summer days in the Arctic within the next few years, researchers have warned.

A study by scientists at the University of Colorado Boulder suggest the first ice-free day in the Arctic Ocean could occur more than 10 years earlier than previous projections.

Greenhouse gas emissions are the main contributors to sea ice loss. As the amount of heat from the Sun absorbed by the ocean increases in the Arctic, warming and melting results.

Analysing sea-ice coverage data from computational climate models to predict how it may change, researchers suggest an ice-free Arctic is “inevitable”.

The team predicts there could be no sea ice in the Arctic Ocean for the first time on a late August or early September day, when levels are traditionally at a minimum, sometime by the beginning of the 2030s under all greenhouse gas emission scenarios.

Under the world’s current path, which researchers refer to as an “intermediate emissions scenario”, the Arctic Ocean might become ice-free by mid-century from August to October.

But in the worst-case, highest-emissions scenario, the Arctic, which is warming more than twice as fast as the rest of the planet, could become ice-free nine months a year, including during some the winter.

“This would transform the Arctic into a completely different environment, from a white summer Arctic to a blue Arctic,” said Alexandra Jahn, associate professor of atmospheric and oceanic sciences and fellow at CU Boulder’s Institute of Arctic and Alpine Research.

"So even if ice-free conditions are unavoidable, we still need to keep our emissions as low as possible to avoid prolonged ice-free conditions."

An ice-free Arctic Ocean is not entirely free of ice but defined as having less than 1 million square km (386,000 square miles) of coverage.

That is less than 20 per cent of the region’s seasonal minimum ice cover in the 1980s.

And it is significantly less than in recent years, when the Arctic Ocean had about 3.3 million square km of sea ice at its minimum in the month of September.

“When it comes to communicating what scientists expect to happen in the Arctic, it is important to predict when we might observe the first ice-free conditions in the Arctic, which will show up in the daily satellite data,” Ms Jahn said.

Declining levels of sea ice have a significant impact on Arctic animals that rely on it for survival, such as seals and polar bears. In addition, as the ocean warms up, researchers are concerned that non-native fish could move into the Arctic Ocean causing an adverse effect on the ecosystem.

The loss of sea ice also poses a risk to the communities living near the coastal region.

Sea ice acts as a buffer to ocean waves crashing on to coastal land, Ms Jahn said.

As the ice retreats, ocean waves are set to get bigger, causing more coastal erosion.

While an ice-free Arctic may be inevitable, Ms Jahn said emission levels will still determine how often the conditions occur.

The researchers stress that Arctic sea ice is resilient and can return quickly if the atmosphere cools down.

“Unlike the ice sheet in Greenland that took thousands of years to build, even if we melt all the Arctic sea ice, if we can then figure out how to take C02 back out of the atmosphere in the future to reverse warming, sea ice will come back within a decade,” she said.

Nasa’s National Snow and Ice Data Centre warned that the average monthly Arctic sea ice in February was the 15th lowest in the satellite record, with temperatures above average but still well below freezing.

It said: ”Based on the linear trend, February has lost 1.84 million square km of ice since 1979. This is equivalent to the size of Alaska.”