CHANGE is afoot at the top of our world. Spring has sprung, marking a crucial moment in the Arctic’s annual cycle. Each year, the ice sheet reaches its maximum extent in March, then begins to shrink as temperature warm up.
But this year, something is different. The floating sea ice, which at its peak normally extends as far as the eye can see and feels as solid underfoot as a continental shelf, is rotten. For the third year in a row, its maximum March extent is at a record low, following a winter of heatwaves. February temperatures were above freezing.
These are the symptoms of a new Arctic that is being created – perhaps the most profound change to the look of our planet for millions of years, with consequences for the rest of the planet. In all likelihood the Arctic Ocean will soon be ice-free in the summer, surrounded by snow-free lands. “We are in a new Arctic regime,” says marine biologist Antje Boetius.
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Follow us as we take you through a year on thin ice.
Winter
In the world’s most northern settlement, an international research town in Svalbard called Ny-Ålesund, the sun sets in the last week of October and doesn’t rise again until mid-February. The polar night ushers in freezing temperatures that are essential for the region’s annual cycle (see video and diagram). As the mercury plummets, ice starts to grow out over the ocean’s dark waters, covering it in a floating ice shelf. Winter has come.
Historically, the ice could grow to be 5 metres thick in places where it survived the summer and thickened with each passing winter. But that is changing. Antje Boetius, at the Max Planck Institute for Marine Microbiology in Bremen, Germany, experienced the new conditions first-hand during an expedition last October. “Areas that showed up on satellites with 100 per cent ice cover often had at best very broken ice. Even when there was ice, it was so thin we could often see through it,” she says. “This rotten ice is causing misleading measurements,” says David Barber at the University of Manitoba in Winnipeg, Canada. Satellites can’t picture the planet’s surface in high enough resolution to show the broken-up ice, which means that many of the usual statistics about ice cover underestimate what’s going on.
Conditions didn’t improve as the winter settled in. A brought temperatures that were as high as -7°C in some parts of the Arctic, 15°C warmer than the average over the past three decades. The repercussions were remarkable. Satellite data collected by the US National Snow and Ice Data Center show that the growth of sea ice slowed down to a crawl at times. Twice – in late November and December – the ice cap actually shrank.
The consequences of the warm winter are likely to be long-lasting. Thin, broken-up ice is far less likely to survive the summer melt and form sustainable multi-year ice. Three decades ago, 45 per cent of ice during the winter maximum was multi-year ice. In March 2016 it was just 22 per cent and this winter is on track to be equally extreme, although the numbers aren’t in yet.
Current climate models don’t come close to predicting the scale of ice loss we’re seeing in the region, says Julienne Stroeve at University College London. “We’re basically about 30 years ahead of where the models say we should be.” Why this is the case is a hot topic. One possibility is that the loss of ice brought about by global warming is being amplified by natural variabilities – decadal weather cycles that have nothing to do with climate change and fossil fuels. Another is that something isn’t quite right in the models. Boetius points out that they don’t properly mimic things like local weather changes due to global warming, and the physical effects of winds and waves that break up ice.
What is clear are the extreme conditions on the ground. The ice cap reached its maximum extent on 7 March this year. At 14.42 million square kilometres, it was .
Fact file: rubbish
• Arctic Ocean litter has increased 20-fold in 10 years
• A 2014 survey recorded off the Fram Strait east of Greenland
Spring
The annual return of sunlight to the Arctic triggers a cascade of events. The rays warm the air and start to melt the snow. Gaps between the sheets of floating ice get wider and the surface of the ocean warms up.
Beneath the ice, a unique food chain is set in motion: as light begins to filter through, photosynthetic algae start to grow in tiny crevices in the ice, feeding tiny crustaceans that in turn feed small fish. At the surface, polar bears emerge from hibernation to seek out seals, while whales move about in the widening cracks between the ice.
The return of light also highlights an important way in which the new Arctic is affecting regions further south: we are losing a vital mirror that helped keep the planet cool. White snow and ice typically reflect 85 per cent of solar radiation back out into space, whereas dark ocean only reflects 10 per cent. As the ice and snow disappear, the ocean’s reflectivity is being almost entirely destroyed.
To calculate how much extra solar heat is being absorbed in the Arctic as the white surfaces turn dark, Ian Eisenman and colleagues at the Scripps Institution of Oceanography in San Diego, California, turned to satellite radiation data. They found that an extra 6.4 watts is being absorbed today for every square metre of the Arctic, compared with 1979.
Fact file: higher seas
• Glaciers on land are flowing into the oceans faster because of climate change, pushing sea levels up worldwide
• Annual ice loss from the islands of the Canadian archipelago has increased 10-fold in 10 years
• Greenland’s glaciers release 250 cubic kilometres of water a year, contributing 40 per cent of annual sea level rise
• If all the ice on Greenland melted, global sea levels would be 7 metres higher
For a sense of scale, the team compared this with the warming effect of carbon dioxide over the same period. They found that the loss of sea ice has delivered a warming boost to the entire planet equivalent to 25 per cent of the effect of rising CO2 levels. This is the main reason why the Arctic has on average been warming more than twice as fast as the planet as a whole over the past half-century.
“You can’t ignore that,” says Eisenman. “The sea ice is an important player in the global climate change that we have observed in the past 30-odd years.” Climate models do include the loss of Arctic reflectivity – also known as albedo – in their calculations of future warming but, he says, the change measured is about twice as large as what models typically predict.
It’s not just sea ice that is disappearing. Snow and ice are vanishing on land, too, and bare tundra reflects just 20 per cent of the sun’s rays. This is also having a large effect, warns Peter Wadhams, an ocean physicist at the University of Cambridge. “The snowline retreat in midsummer is now 6 million square kilometres, compared to the 4 million square kilometres loss of sea ice,” he says, adding that the warming effect of darker land masses could be as big as that from lost sea ice. The calculations are rough, but the message seems clear: the Arctic is amplifying global warming on a large scale.
Summer
Arctic summers are greener and more lively these days. Average June snow cover has declined by 58 per cent since 1979, exposing more tundra for longer. Howard Epstein of the University of Virginia in Charlottesville has measured a 20 per cent increase in plants on the tundra since 1982. Woody shrubs are spreading at the expense of more distinctive local species such as the lichen that are an important food source for reindeer.
Coastlines are also being transformed. Waves are pounding shorelines that ice once protected. According to Irina Overeem at the University of Colorado, erosion rates along the coast of the Beaufort Sea have more than doubled in half a century to an average of 14 metres a year.
In some ways, the greening of the tundra is good news. It is extracting CO2 from the atmosphere, which helps to counteract global warming. But many predict this helpful feedback could soon be overwhelmed by the release of CO2 and methane from melting permafrost on land and ocean sediments. The frozen Arctic traps an estimated 1500 billion tonnes of organic carbon, twice the amount of CO2 in the atmosphere. Under controversial doomsday scenarios, large quantities could be belched into the atmosphere, pushing global temperatures up by a further 1°C or more.
Meanwhile, we are only just discovering the richness of life in the Arctic. Last year, Boetius led an expedition to Karasik Seamount, a submerged summit in a mid-ocean ridge just 400 kilometres from the North Pole, to document the world’s northernmost known coral. The Arctic Ocean is a vast and largely unexplored space, and Boetius was stunned by the diversity she saw: “Huge white starfish, blue snails, red crabs and brown clams, between huge globular sponges that are up to a metre across and hundreds of years old.”
Her fear is that all this may be lost before it is even found – an ice-free Arctic will be a very different environment favouring a very different style of life. Recent years have seen on the Alaskan and Siberian coasts of the Chukchi Sea, taking a breather on land because the sea ice from which they normally hunt had disappeared. The new behaviour has resulted in overcrowding, stampedes that are deadly to young calves, and food shortages.
It’s not just behaviours that have changed. Melt the snow, warm the water, remove the ice that once kept the waters dark, and we can expect a biological cornucopia. According to the US National Oceanic and Atmospheric Administration, last year the Barents Sea north of Scandinavia had 19 per cent more biomass than the average for 2003 to 2015. That could be the start of a predicted 70 per cent increase in the Arctic Ocean’s biomass production. At the base of the ocean’s food chain, phytoplankton have increased by 20 per cent since 1998 thanks to more open water.
On top of this, Atlantic species are moving north, lured by more food and warmer waters. Some call this the “Atlantification” of the Arctic. In her latest expedition, Boetius found haddock at 85° north, just 550 kilometres from the North Pole. The fish are primarily a North Atlantic species and don’t normally stray further north than Svalbard. Others have shown that both Atlantic and Pacific cod have also moved in. The concern is that an influx of newcomers could crowd out and even kill off the natives. Arriviste orcas, for instance, are hunting native narwhals in the archipelagos of northern Canada.
Fact file: ocean grab
• Russia planted its flag on the ocean floor at the North Pole in 2007, kick-starting a dispute over who owns the Arctic
• The carve-up is likely to be done by the Arctic Council, an intergovernmental club of all eight Arctic nations
• The US Geological Survey estimates that 30 per cent of the world’s undiscovered natural gas could be in the region
• Ice-free Arctic waters could also halve the journey time for cargo from China to Europe
Autumn
September marks a second turning point in the Arctic’s annual cycle – known as the ice minimum – and one day soon it will be monumental. This is the point in the year when the shrinking stalls for a few days before winter starts up again and the cycle repeats. With 4.14 million square kilometres of ice, last September’s minimum was tied with 2007’s as the second smallest on record.
The downward trend is reliable, and according to the most pessimistic climate researchers, an ice-free September is just years away. Wadhams is in this camp, that he expects the first ice-free summer to be in 2017 or 2018. It’s worth noting that what scientists have agreed to call “ice-free” in fact makes allowances for 1 million square kilometres of ice, most of which will be packed up against the region’s convoluted coastlines and inside the Canadian archipelago, where the ice is thickest.
Wadhams is definitely at the extreme end of predictions. In practice, several factors – including natural variations in the weather from year to year – make it difficult to pinpoint the first ice-free summer with that degree of precision. A study estimated that any forecasts must have an error bar of roughly 25 years. With that in mind, the first ice-free summer could be between 15 and 36 years away if greenhouse gas emissions remain high, estimate Alexandra Jahn at the University of Colorado and colleagues. This could be delayed by a decade or so if we were to reduce emissions.
Can anything be done to save the Arctic’s ice? Stroeve reckons only the 2015 Paris Agreement’s aspirational target of halting global warming at 1.5°C would deliver a realistic chance of this. Some fear the region may soon pass a threshold beyond which the warming effect caused by the loss of reflective ice is sufficient on its own to melt most of what’s left. That would be irreversible, and could unleash runaway global warming that would continue whatever we did to emissions. Eisenman calculates that this is unlikely before all the summer ice is gone, but perfectly possible thereafter.
We always knew a warmer world would be different, with deserts spreading north, super El Niños, conflagrations in the rainforests and more intense hurricanes bubbling up above the hot oceans. Many saw the melting Arctic as a largely passive victim of that climate change. No longer. Feedbacks from an ice sheet that has vanished faster than anticipated mean a new Arctic is alive and kicking.
Arctic ice, your weather
What happens in the Arctic doesn’t stay in the Arctic. Studies show that the shrinking ice cap is effectively helping to warm the rest of the planet (see Spring). It may also be changing your local weather. Jennifer Francis at Rutgers University in New Jersey has pointed out that rapid warming in the north is reducing the difference between Arctic and mid-latitude air temperatures. That difference drives the northern jet stream, which moves weather systems around the hemisphere. So changes in the Arctic may explain a 10 per cent decline in its speed since 1980, she says.
The slower jet stream has begun to meander more. Instead of pushing weather systems along, it traps them in one place, creating longer summer droughts and winter cold spells.The frequency of such stalled weather systems in summer has doubled since 2000, says Dim Coumou of the Potsdam Institute for Climate Impact Research in Germany. He blames this for the heatwave and forest fires in Russia in 2010, the drought in North America in 2012 and Europe’s killer heatwave in 2003. Francis suggests it could also explain persistent cold spells in east Asia.
Some researchers say weird weather can never be attributed to a single cause in this way. Francis agrees it may be a long time before we can be sure she is right. But if the new Arctic causes the jet stream to slow permanently, Europeans and North Americans could be in for a bumpy ride of climate extremes.
This article appeared in print under the headline “A year on thin ice”
Article amended on 2 May 2017
We placed the haddock correctly.
