永久冻土层正在融化

永久冻土层正在融化

The Permafrost Tunnel Research Facility, dug in the mid-1960s in Fairbanks, Alaska, allows scientists a three-dimensional look at frozen ground.

1960年代中期在阿拉斯加费尔班克斯挖掘的永久冻土层隧道研究设施，使科学家能够对冻土层进行三维观察。

In 2018, we reported on concerns that zombie pathogens — ancient bacteria and viruses that could potentially rise from the dead and threaten humans if the layers of frozen permafrost where they're buried thaw as the Earth warms. The consensus among the scientists interviewed was: It's unlikely — although there was one tantalizing anecdote about a scientist whose knee may have become infected after contact with a defrosted seal. But we did want to follow up and see what the latest research says about thawing permafrost — and have learned of another threat posed by its demise.

2018年，我们报道了僵尸病原体——一种古老的细菌和病毒，如果它们被埋的永久冻土层随着地球变暖而解冻，它们可能会从死人身上复活并威胁人类。接受采访的科学家的共识是:这是不可能的——尽管有一个有趣的轶事，说是一位科学家的膝盖可能在接触解冻的海豹后感染了。但我们确实想跟进，看看关于永久冻土层融化的最新研究是怎么说的，并了解到冻土层的消亡带来的另一个威胁。

It's not just warmer temperatures that pose a problem for the permafrost. Scientists are now investigating whether rainfall could be causing serious issues in the Arctic's permafrost – with repercussions for humans.

对永久冻土层造成问题的不仅仅是温度的升高。科学家们正在调查降雨是否会给北极的永久冻土层带来严重的问题，并对人类造成影响。

Since 2013, Fairbanks, Alaska, has had two of the wettest years in recorded history. A total ofo 14.6 inches of rain fell in the summer of 2014; it was the wettest summer yet. And that's not a good thing for permafrost, says Thomas Douglas, a geochemist in the U.S. Army Corp of Engineers.

自2013年以来，阿拉斯加的费尔班克斯经历了有记录以来最潮湿的两年。2014年夏季降雨量为14.6英寸;这是迄今为止雨水最多的夏天。美国陆军工程兵团的地球化学家托马斯·道格拉斯说，这对永久冻土层来说不是一件好事。

Permafrost — completely frozen ground composed of materials like soil, rocks and even bones and plants — makes up a nearly a quarter of the Northern Hemisphere. Much of it has been frozen for thousands of years.

永久冻土层——由土壤、岩石甚至骨骼和植物等物质完全冻结的地面——占据了北半球近四分之一的面积。它的大部分已经冻结了数千年。

Warming temperatures have begun to thaw permafrost, and now, increased rainfall seems to be intensifying the problem, according to Douglas' latest study in Climate and Atmospheric Science, published in July.

根据道格拉斯7月份发表在《气候与大气科学》上的最新研究，不断变暖的气温已经开始融化永久冻土层，而现在，降雨量的增加似乎正在加剧这个问题。

"In general, across the arctic, the thought is that things are getting wetter," Douglas says, but particularly in Fairbanks. "2014 and 2016 were the #1 and #3 summer precipitation years in what was then a 90-year record. Shattering records like this is just really unique."

道格拉斯说:“总的来说，整个北极地区的气候都在变得越来越湿润。”但费尔班克斯地区的情况尤其如此。2014年和2016年分别是夏季降水量排名第一和第三的年份，这在当时是90年来的记录。打破这样的记录真的是独一无二的。”

To figure out how this increased rainfall affects permafrost, Douglas and his team studied three permafrost sites for five years. He and his team focused on "active layer" permafrost, the very top layer of permafrost that naturally thaws in the summer and refreezes in the winter.

为了弄清楚增加的降雨是如何影响永久冻土层的，道格拉斯和他的团队用五年时间研究了三个永久冻土层。他和他的团队专注于永冻层的“活动性层”，即永冻层的最顶层，在夏季自然解冻，在冬季再次冻结。

To study this layer, his team measured how deep it went at the end of each summer, right when the permafrost was at maximum thaw. They made the measurements using a frost or thaw probe.

为了研究这一层，他的团队在每年夏末，也就是永久冻土层融化最剧烈的时候，测量了它的深度。他们使用冰霜或解冻探测器进行测量。

"We take a metal rod with a handle on it and we shove it down into the ground until it makes a thump noise," Douglas explains. That's when they know they've hit frozen permafrost. A ruler on the side of probe tells the user how far down the rod is in the ground.

道格拉斯解释说:“我们拿一根有把手的金属棒，把它往地下推，直到它发出砰的一声。”那时他们知道他们已经接触到冰冻的永久冻土层。探针侧面的尺子可以告诉使用者杆子在地下的深度。

Between 2013 and 2017, the team took more than 2,500 measurements — and they started to see a pattern. The more it rained, the more the layer of thawed permafrost grew in the summer.

在2013年到2017年之间，该团队进行了2500次测量，他们开始看到了一个模式。在夏季，雨下得越多，永久冻土的解冻面积就越大。

The thaw was worse in some locations more than others, depending on the terrain where measurements were taken. Forests and mossy landscapes seemed to protect the permafrost. There, for every additional inch of rain, the permafrost thawed by an additional quarter of an inch.

根据测量地点的地形，有些地方的解冻情况比其他地方更糟。森林和长满苔藓的景观似乎能保护永久冻土。在那里，每多下一英寸的雨，永久冻土就会融化四分之一英寸。

But in locations where human activity – such as trails and clearings — had altered the land, the thaw was worse. For every additional inch of rain, the researchers saw an additional inch of thaw. At one particular site, permafrost thaw depth grew from 47 inches in 2013 to nearly 75 inches in 2017.

但在人类活动改变了土地的地方(比如步道和空地)，解冻情况更糟。每增加一英寸的降雨，研究人员就会看到一英寸的融化。在一个特定地点，永久冻土融化深度从2013年的47英寸增加到2017年的近75英寸。

Douglas explains, "When you remove vegetation, that's like leaving the lid open on your cooler on a summer day. It allows heat and water to get down in the permafrost pretty rapidly."

道格拉斯解释说:“当你移除植物时，就像在夏天把冷却器的盖子打开一样。它能让热量和水迅速进入永久冻土层。”

Out of all the team's research, Douglas says their most important finding was that thinner layers of thawed permafrost seem to be vanishing — literally thawing away.

道格拉斯说，在研究小组的所有研究中，他们最重要的发现是，变薄的永久冻土似乎正在消失——实际上是在融化。