Arctic sea ice cover fell to its second lowest level on record this summer, continuing a “dramatic” downwards trend that is disrupting marine ecosystems and making life for indigenous people in the region ever more precarious.

The National Oceanic and Atmospheric Administration (NOAA) annual report card on the state of the Arctic found that the average annual air temperature was 1.9C above the long-term average, taken from 1981 to 2010, the second highest it has been since observational records began in 1900.

The warmer conditions meant that ice froze later in the winter and melted sooner in the summer, reducing the extent of Arctic sea ice at the end of the summer to the second lowest level since satellites began monitoring ice coverage 41 years ago.

On 18 September 2019, when the sea ice was at its minimum, it covered 4.15m sq km, a 33% drop and more than 2m sq km smaller than the long-term average minimum for the time of year.

“It’s more alarming each year that we have this situation,” said Donald Perovich, a co-author on the report and professor of engineering at Dartmouth College in New Hampshire. “I approach every report card with a sense of trepidation: is this going to be the year we have another big decrease?”

“When we look at the end-of-summer ice extent, the 13 smallest years have all been in the past 13 years. There was a large decrease in 2007 and we have never returned to the levels before that,” he added.

The greatest amount of Arctic sea ice was observed on 13 March 2019, with end-of-winter coverage extending over 14.78msq km, down 5.9% on the long term average maximum, and the seventh lowest in the satellite record.

The oldest ice, which is more than four years old, once dominated the Arctic, but now makes up a mere fraction of the ice pack. In March 1985, old ice accounted for 33% of Arctic sea ice, but only 1.2% in March this year.

“Overall, the Arctic sea ice cover has transformed from an older, thicker, and stronger ice mass in the 1980s to a younger, thinner, more fragile ice mass in recent years,” said the report, which was unveiled on Tuesday at the American Geophysical Union conference in San Francisco.

Q&A How is climate change affecting the Arctic? Show Hide The world may have warmed by around 1C (1.8F) over the past century but the Arctic far outstrips this global average and is warming at around twice the rate of the rest of the world. In places, the rate of warming has been astonishing. Novembers in the Alaskan town of Utqiaġvik, formerly Barrow, are now 5.5C warmer than they were in 1979. In the summer of 2019, an Arctic heatwave saw parts of Greenland reach temperatures 40C hotter than normal. The Arctic is dominated by sea ice, unlike the Antarctic which is essentially a huge land-based ice sheet. As the ocean and atmosphere warm, sea ice is shrinking in extent, at around 13% a decade since 1979, according to Nasa. The bright white surface of ice, known as albedo, is giving way to the dark ocean, meaning that sunlight is being absorbed rather than reflected, amplifying the warming effect. These "rapid" and "unprecedented" changes are transforming the Arctic and threatening traditional ways of life, according to US government scientists in a 2019 report card. The sea ice is younger, thinner, more fragile and less extensive, making hunting on the ice harder and more perilous. The marine ecosystem is shifting as warmer water forces fish species to retreat to more northern waters. What is a major challenge to communities in the Arctic, is a boon to the shipping industry, which can navigate the area more easily. This task will get even simpler once the Arctic is ice free in summertimes, forecast as soon as 2040s.

In Greenland, a summer heatwave produced melting on a par with the worst years ever, with satellite data from 2002 to 2019 showing that the ice sheet has lost on average about 267bn tonnes of ice per year.

The Arctic is particularly vulnerable to the climate crisis, with annual air temperatures rising twice as fast as the global average. Part of the reason is that sea ice reflects the sun’s rays back out to space, and as it melts, a feedback cycle kicks in whereby retreating ice exposes more sea water which absorbs more heat and drives more melting.

The warming temperatures are already disrupting life for more than 70 indigenous communities that live around the Bering Sea, where sea ice narrowly missed setting a record low this year. Hunting on the ice is becoming more hazardous and access to subsistence foods is shrinking, the report’s authors found. As the region warms, Arctic fish species are retreating to more northerly waters.

“These changes are creating a world that we are not going to like, with more storms and higher sea levels. The time is now to start doing everything we can, to reduce carbon dioxide in the atmosphere, and to put out less carbon dioxide, because that is what is driving this,” said Erich Osterberg, as associate professor of Earth Sciences at Dartmouth College, who was not involved in the report.

“These are huge and scary changes even for us scientists who do this for a living,” he added. “It’s dramatic. It’s really just in the last decade or two that these changes have gone off the charts.”

Jack Landy, who studies Arctic sea ice at Bristol University, said: “We are crossing into a new frontier in the Arctic, where large regions like the Chukchi Sea – once covered by sea ice all year round – can now be ice-free deep into winter.

“There is a consensus among scientists that Arctic sea ice cover has a far rosier future if we keep global temperatures to 1.5C, rather than 2C, above pre-industrial levels,” he added.