It is likely that many people alive today will see the end of the Arctic as we know it. The vast expanses of summer sea ice trod by polar bears, the pods of narwhals coursing by, the day-long herds of caribou crossing the tundra, all are threatened by current and future climate change. This change will have an impact on life in the Arctic, and in the rest of the world. This is the stark conclusion from the most complete assessment of Arctic climate in six years. – polar ecologist Martin Sommerkorn, writing in The Arctic Journal.

The accelerating pace of climate change in the world’s Arctic regions has been much in the news for a few years now, but still it is astonishing to see the findings issued Tuesday by a science group that advises the eight-nation Arctic Council.

Rates of warming are now known to be much more rapid than was recognized as recently as 2011, and temperatures have reached levels that cannot not be reversed by any conceivable human actions in the remainder of this century. Among the consequences:

• Melting permafrost that is collapsing roads, felling forests and absorbing building foundations from Siberia to Alaska, while threatening massive new releases of globe-warming methane.
• Wildfire regimes more severe than can be found in the record for at least 10,000 years, along with worsening patterns of tree-killing insect infestations driven by warmer, drier conditions.
• Continuing shrinkage of the sea-ice season at both ends, with a virtual end to all summer ice now probable within about 20 years, along with winter losses that threaten the habitat not only of whales, walrus, seals and bears but the existence of communities that subsist on ice-dependent hunting and fishing practices.
• Glacial ice and snow melt at rates that will drive global sea levels well above the most recent predictions of the Intergovernmental Panel on Climate Change.

The Arctic Council is a 20-year-old joint effort of the United States, Russia, Canada, Sweden, Denmark, Norway, Finland and Iceland, which exists to track climate and inform policy responses by its members. You could see it a small-scale version of the IPCC.

The council in turn is informed by scores of scientists working through the Arctic Monitoring and Assessment Programme to gather, review and synthesize the best science available.

Council convenes in May

AMAP’s first report on “Snow, Water, Ice and Permafrost in the Arctic: Summary for Policy-Makers” came out in 2011. Its second was published on Tuesday in advance of the council’s annual ministerial meeting, which convenes May 11 in Fairbanks, Alaska.

One item of business will be a handoff of the council chairmanship from the United States to Finland, which from a polar bear’s view is a good and a timely thing, considering the Trump administration’s hostile indifference to climate science.

But the main focus will be on what that science shows about how “the Arctic as we know it is being replaced by a warmer, wetter and more variable environment,” with “profound implications for people, resources and ecosystems worldwide.” Key excerpts:

The Arctic was warmer from 2011 to 2015 than at any time since instrumental records began in around 1900, and has been warming more than twice as rapidly as the world as a whole for the past 50 years. January 2016 in the Arctic was 5°C warmer than the 1981–2010 average for the region, a full 2°C higher than the previous record set in 2008, and monthly mean temperatures in October through December 2016 were 6°C higher than average for these months. Sea temperatures are also increasing, both near the surface and in deeper water.

Sea ice thickness in the central Arctic Ocean declined by 65% over the period 1975–2012 …. [continuing] a long-term downward trend. A record low minimum sea ice extent occurred in 2012 and a record low maximum sea ice extent occurred in 2016. Older ice that has survived multiple summers is rapidly disappearing; most sea ice in the Arctic is now ‘first year’ ice that grows in the autumn and winter but melts during the spring and summer.

Since at least 1972 the Arctic has been the dominant source of global sea-level rise. Seventy percent of the Arctic’s contribution to sea-level rise comes from Greenland, which on average lost 375 gigatons of ice per year—equivalent to a block of ice measuring 7.5 kilometers or 4.6 miles on all sides—from 2011 to 2014. This is close to twice the rate over the period 2003–2008.

After the Greenland ice sheet, the largest Arctic contributions to sea-level rise will come from glaciers in the Canadian Arctic, Alaska, and the Russian Arctic, along with glaciers surrounding the Greenland ice sheet. when all sources of sea-level rise are considered (not just those from the Arctic), the rise in global sea level by 2100 would be at least 52 cm for a greenhouse gas reduction scenario and 74 cm for a business-as-usual scenario. These estimates are almost double the minimum estimates made by the IPCC in 2013.

The report estimates the global costs of responding to Arctic climate change at somewhere between $7 trillion and $90 trillion by the end of the century. Big numbers, but quite a range between them.

Good for shipping, bad for roads

At local and regional scales, the report is rife with examples of what lies ahead, often based on what’s already happening.

Transportation via ship will benefit as the shrinking ice extends the open-water season, which has already increased by one to three months since the late 1970s, depending on location.

However, thawing of surface water and permafrost is collapsing ice roads, on which many rural communities are dependent, and also promoting more landslides (a problem lately for the Bovanenkovo gas field in Siberia) and spring flooding (which cut the Dalton Highway to Alaska’s North Slope oil fields for three weeks in 2015).

The softening of permafrost threatens the stability of homes and other buildings, such that “the bearing capacity of building foundations has declined by 40-50% in some Siberian settlements since the 1960s.” The thaws also threaten to taint freshwater resources with pollutants that had been locked in ice.

Shortening of the pack-ice season along Arctic coasts is promoting faster erosion of shoreline lands and exposing coastal villages to higher risks of damage from storm-driven waves.

Most of these scenarios may be at least partly avoidable, in theory.

The report concludes that if all the objectives of the Paris accord on climate change were met, “the duration of snow cover would stabilize at roughly 10 percent below current values by the end of the century, and permafrost losses would stabilize at 45 percent of present day levels.”

Out of date before publication

That is, if the pace of change as currently measured remains the same. But as Walter Meier, a NASA scientist who helped prepare the report, explained to Sabrina Shankman at  Inside Climate News, the forecasting is confounded by both the increasing rates of Arctic change and the slow pace of scientific study and publication – including the peer-review process that this report went through, which can consume a year or longer.

“The report is almost out of date before it gets published,” he said.

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While we’re on the topic of rapid, climate-driven shifts in Arctic systems and landscapes, consider this stunner reported Monday in the journal Nature Geoscience:

In a process that normally takes at least thousands of years, a river in the Kaskawulsh Glacier of Canada’s Yukon Territory reversed course in a matter of months last year.

Instead of flowing north  to the Bering Sea, via the Slim and Yukon rivers, the water is now heading south to the Pacific Ocean. And the cause was unusually warm spring weather that enabled the meltwater to cut a new channel through normally frozen terrain at comparatively breakneck speed.

It’s an example of a process that geologists call “river piracy,” and according to a fine piece by John Schwartz in The New York Times, this form of riparian theft “has generally been associated with events such as tectonic shifts and erosion occurring thousands or even millions of years ago. Those earlier episodes of glacial retreat left evidence of numerous abandoned river valleys, identified through the geological record.”

Not any more, at least in parts of the far north, where “radical reorganizations of drainage can occur in a geologic instant” – in this case, draining a lake and isolating a bunch of  cabins reachable only by boat, and turning a rushing watercourse into a canyon that’s pretty much silent and dry between dust storms.