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更新时间:2017/11/8 19:17:58 来源:本站原创 作者:佚名

The great thaw of america's north is coming

Vladimir Romanovsky walks through the dense black spruce forest with ease. Not once does he stop or slow down to balance himself on the cushy moss beneath his feet insulating the permafrost.

弗拉基米尔·罗曼诺夫斯基(Vladimir Romanovsky)轻松稳步地穿过茂密的黑云杉树林,脚下踩着的是隔绝着冻土层的松软苔藓。

It’s a warm day in July, and the scientist is looking for a box that he and his team have installed on the ground. It’s hidden nearly six miles (10km) north of the Geophysical Institute at the University of Alaska in Fairbanks, where he’s a professor of geophysics and heads the Permafrost Laboratory.

这是七月里温暖的一天,这位科学家正在寻找一个他和他的小组安放在地下的盒子。这个盒子隐藏在阿拉斯加大学费尔班克斯分校(University of Alaska Fairbanks)地球物理研究所(Geophysical Institute)以北近六英里(10公里)的某处,而罗曼诺夫斯基则是该研究所的地球物理学教授和永冻土实验室(Permafrost Laboratory)主任。

The box, which is covered by tree branches, contains a data collector connected to a thermometer installed below ground for measuring permafrost temperature at different depths. Permafrost is any earth material that remains at or below 0C (32F) for at least two consecutive years.


Romanovsky connects his laptop to the data collector to transfer the temperature data for this location – called Goldstream III – which he will later add to an online database accessible to both scientists and interested individuals.

罗曼诺夫斯基将他的笔记本电脑与数据采集器相连,并将这一称为金溪三号(Goldstream III )的地点的温度数据上传,稍后他会将这些数据添加到一个在线数据库,供科学家和感兴趣的个人访问。

“Permafrost is defined on the basis of temperature, the parameter that characterises its stability,” Romanovsky says.


When the temperature of permafrost is below 0C (32F), for example -6C (21F), it is considered stable and will take a long time to thaw or to change. If it's close to 0C, however, it's considered vulnerable.


Every summer the portion of soil overlaying the permafrost, called the active layer, thaws, before refreezing the following winter. At Goldstream III, on this July day, the summer thaw currently ends at 50cm depth.


As the Earth warms and summer temperatures climb, the thaw is deepening and expanding, causing the permafrost underneath to become less stable.


The consequences, if this thawing continues, will be profound, for Alaska – and for the world. Nearly 90% of the state is covered in permafrost, which means entire villages will need to be relocated, as the foundations of buildings and roads crumble. And if this frozen cache releases the millennia of accumulated carbon it has locked within, it could accelerate the warming of our planet – far beyond our ability to control it.


A vulnerable state


As permafrost thaws, houses, roads, airports and other infrastructure built on the frozen ground can crack and even collapse.


“We are seeing some increased maintenance on existing roads over permafrost,” says Jeff Currey, materials engineer for Northern Region of the Alaska Department of Transportation Public Facilities. “One of our maintenance superintendents recently told me his folks are having to patch settling areas on the highways he's responsible for more frequently than they were 10 or 20 years ago.”

"我们注意到,修建在永冻土层上的道路的维护工作在增加,"阿拉斯加州交通运输部公共设施处(Alaska Department of Transportation Public Facilities)北部地区(Northern Region)的材料工程师杰夫·库里(Jeff Currey)说,"我们的一个维修主管最近告诉我,相比10年或20年前,他们对高速公路区域内的地面沉降进行的修补更为频繁。"

Similarly, infrastructure built underground – such as those for utilities – is suffering as temperatures rise.


“In Point Lay – on the coast in northwest Alaska – for instance, they're having all sorts of trouble with their water and sewer lines buried in permafrost soil,” says William Schnabel, director of the Water & Environmental Research Center at the University of Alaska Fairbanks. “The permafrost soil has thawed and we get water and line breaks because the ground shifts.”

"例如在阿拉斯加西北海岸的波因特莱(Point Lay),那里建在永久冻土中的自来水管线和下水道遇到了各式各样的麻烦,"阿拉斯加大学费尔班克斯分校的水与环境研究中心(Water & Environmental Research Center )主任威廉·施纳贝尔(William Schnabel)说:"永久冻土的融化,导致地层移位,使得输水管道破裂。"

The concern is even more pronounced for those living in rural areas who don't have enough funds to combat the effects of thawing permafrost. For those residents it's not just about collapsing buildings, which is common now, but also water supply.


Often as permafrost thaws on the side of a lake that a village might use as water supply, there’s a breach and a lateral drain occurs. “It usually requires pretty expensive infrastructure to take water from a lake, bring it to a village and store it and all the components of this infrastructure are vulnerable to thawing permafrost,” Romanovsky says.


If a village depends on an affected lake for water, the community members would have to move their infrastructure and sometimes their entire village to another lake, which can be very costly.


According to research conducted by US Geological Survey, villages like Kivalina in north-west Alaska will have to move within the next 10 years, Romanovsky explains. “But estimates show cost of moving is about $200m (£150m) per village of 300 people.”

据美国地质调查局(US Geological Survey)进行的研究,在阿拉斯加西北部的那些村庄,例如基瓦利纳村(Kivalina),不得不在未来10年迁走,罗曼诺夫斯基解释说,"但是估算显示,一个300人的村子的搬家成本约为2亿美元(1.5亿英镑)。"

Those kinds of sums are only possible with federal government funding – but there are also no guarantees that a new location wouldn’t be affected eventually too.


“I think by now there are 70 villages who really have to move because of thawing permafrost,” Romanovsky says. “But moving villages to another location on permafrost is very difficult to guarantee for 30 years or so and the federal government doesn't want to pay for something they have to pay for again.”


It’s possible that building Alaskan settlements on permafrost may also be making the problem worse. “When you think about water and sewers you have to keep those above freezing and when you have permafrost you have to keep that below freezing,” Schnabel says. “So you're running relatively warm water through the permafrost and there's going to be some heat dissipation in there.”


Similarly, when a road is built, a lot of the vegetation that insulates the permafrost is cleared and then paved over with black covering that increases the amount of absorbed solar radiation. So although the maintenance burden has increased for those like Currey, not all the distress that comes with infrastructure can be solely attributed to a changing climate.


Defrosting a freezer full of carbon


Alaska, no doubt, is on the front lines of climate change, but the issues related to permafrost aren’t just specific to The Last Frontier. What happens to the frozen earth material in the 49th state will affect the lower 48, as well as the entire globe.


According to Romanovsky, half of the state’s and 90% of interior Alaska’s permafrost will thaw if there’s a global average rise of 2C in air temperature.


This is especially worrying because an enormous amount of organic carbon is sequestered in permafrost and the overlaying active layer. Since there’s not enough heat in frozen soil to help microbes to decompose dying vegetation, over thousands of years organic matter has accumulated in permafrost. Some estimates say the amount of carbon in the permafrost is more than two times than there is in atmospheric carbon dioxide.


“If we maintain our current course of operation, business as usual they call that, then it's pretty certain by 2100 a significant fraction of the permafrost in the upper five metres would thaw out and with it all the organic matter that is currently frozen in the permafrost,” says Kevin Schaefer, a research scientist at the National Snow and Ice Data Center at the University of Colorado. “That would indicate a release of carbon dioxide and methane, which would amplify the warming due to the burning of fossil fuels.”

"如果我们保持目前的行为方式不变,那么可以肯定的是,到2100年,地表上层5米深度的一大部分永久冻土会解冻,连带现在冻结在其中的所有有机物,"科罗拉多大学(University of Colorado)国家雪冰数据中心( National Snow and Ice Data Center)的科学家凯文·谢佛(Kevin Schaefer)说,"这意味着二氧化碳和甲烷的释放,这将加剧化石燃料燃烧造成的气候变暖。"

In fact, in a 2012 report published in the journal Nature, Schaefer and his co-authors indicated that past sudden warming events were essentially triggered by the release of carbon dioxide and methane from permafrost some 50 million years ago in Antarctica.


And the projected numbers don’t look promising: “Theoretically if this carbon is released to the atmosphere, the amount of CO2 will be three times more than what is in there [in the atmosphere] now,” says Romanovsky.


So it's a true feedback loop as it amplifies the warming due to the burning of fossil fuels. And despite the fact that the warming is accelerating, the feedback effects will be gradual, taking time to be noticeable. “It's a very slow feedback,” Schaefer says.  “Imagine trying to steer a steam ship with a canoe paddle, that's the kind of feedback we're talking about.”


Unfortunately, once permafrost starts to thaw, it’ll be hard to refreeze it again – at least in our lifetime. Furthermore, once the decay is out of the ground and into the atmosphere, there’s no easy way to put that carbon back into the ground.


“The only way to do that would be to lower the global temperature and refreeze the permafrost, which would mean you're removing carbon dioxide from the atmosphere,” Schaefer says.


Climate models show that current intergovernmental commitments to reduce warming – as laid out by the Paris Climate Accord – may not be enough, Romanovsky explains.


In a 2016 report published in Nature Climate Change, researchers Sarah Chadburn and colleagues estimate that even if the climate was stabilised as agreed upon by the 196 parties in 2015, “the permafrost area would eventually be reduced by over 40%”.

在一篇2016年发表在《自然气候变化》(Nature Climate Change)上的报告中,研究人员萨拉·查德博恩(Sarah Chadburn)和她的同事们估计,即使按照196个缔约方在2015年所达成的协议,并且气候最终稳定下来,"永久冻土区域最终将缩水40%以上"。

However, with US President Donald Trump’s announcement of withdrawal from the Paris agreement last June, more permafrost loss is likely on the horizon.


The blame game


Alaska is a politically conservative state, so outsiders might assume that residents reject the idea that the planet is warming beyond our control. The truth is more complex.


According to a poll of 750 participants conducted earlier this year by the Alaska Dispatch News, more than 70% of Alaskans are concerned about the effects climate change.

根据《阿拉斯加递信报》(Alaska Dispatch News)今年早些时候对750名参与者所做的一项民意调查,超过70%的阿拉斯加人关注气候变化的影响。

“In Alaska anybody you ask will say ‘yes there's warming,’” Romanovsky says. “The farther north you go, northwest especially, the stronger that feeling. Because it's happening, you see it. Of course, the question of who's responsible depends on political beliefs.”


At Denali National Park & Preserve, park ranger Anna Moore has witnessed warming affect wildlife across only a couple of years. She’s noticed that the Arctic hare, which switches between brown and white coat colours with the seasons can’t seem to keep up with the changes as a result of temperature rise, essentially putting itself at risk.

在丹奈利国家公园保护区(Denali National Park & Preserve),公园的护林员安娜·摩尔(Anna Moore)见证了气候变暖在过去两三年间对野生动物的影响。她注意到原本随着季节的变化而在棕色和白色毛皮颜色之间切换的北极兔,由于气温上升,似乎赶不上季节的变化,实际上把自己置于危险境地。

“In the wintertime they get white tips to their hair,” Moore says. “As it gets warmer, the snow is melting faster, but their bodies are acclimatised to certain temperature change and so even though the snow is already melting they're still white and in more danger from predators.”


Moore says though she believes in climate change and is watching it affect flora and fauna at the park, she considers it a result of both human activities and a natural cycle.


Her colleague Ashley Tench also echoes the sentiment: “I agree with her [on] how it's part man-made and also natural.” To that effect, Tench doesn’t believe the United States’ pullout of the Paris Agreement makes a difference in the climate.

她的同事艾什莉·坦奇(Ashley Tench)也呼应了这种想法:"她关于部分人为和部分由于自然的观点我也赞同。"为此,坦奇不相信美国退出巴黎气候协定对气候变化有什么影响。

But not everyone in Alaska is on board with that sentiment. To Bill Beaudoin, a retired submariner and educator who’s now the proprietor of a bed and breakfast in Fairbanks, it’s obvious that humans are to blame and that we should work on reversing the effects of our actions.

但并不是每个阿拉斯加人都是这种想法。比尔·博多恩(Bill Beaudoin),是一位现在费尔班克斯市经营民宿的退休潜艇水兵和教育家。他觉得很明显,人类是罪魁祸首,我们应该努力扭转我们行为的影响。

“I think the Paris climate accord was necessary,” he says. “In fact, I didn't think [it was] enough. There's one country, Nicaragua, that didn't sign on to the agreement because they didn’t think it was strong enough. I would probably side with Nicaragua on that issue.”


No matter who is to blame for the warming and resulting thaw of permafrost, Alaskans are for the most part concerned about their future.


“People are worried, because of course there's no insurance for thawing permafrost,” Romanovsky says. “Insurance is not covering damage from permafrost like it does in California for earthquakes.”


Back at Goldstream III, Romanovsky notes that at 50cm depth, the temperature of the soil is -0.04C (31.9F). At one metre it’s -0.23C (31.5F).  The last time he checked the data was in March, where at one metre, the soil temperature measured -1.1C (30F).


He takes his shovel and makes a hole in the ground to look at the soil and check for carbon within. Darker soil indicates accumulated organic carbon. The further down he digs, the colder the soil gets. Romanovsky digs until the shovel hits the permafrost and seemingly can’t go any further.


He pushes down a bit more and manages to dig up a bit of the permafrost – about the size of a small coin. Seconds after he holds the frozen soil between his fingers it melts as if it were an ice cube. He returns the dug up dirt back into the hole, disconnects his laptop from the data collector, closes up the box and covers it up with branches and packs up to leave the site. In a week he’ll head up north to log the temperature at other sites adding yet more data to one of the most comprehensive permafrost databases in the world.


Meanwhile, bit by bit, America’s frozen north is thawing and what happens next is unknown. What’s certain is the great thaw will forever change a once-familiar landscape – and likely a planet and its inhabitants too.