永久凍土層正在融化

永久凍土層正在融化

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費(fèi)爾班克斯挖掘的永久凍土層隧道研究設(shè)施，使科學(xué)家能夠?qū)鐾翆舆M(jìn)行三維觀察。

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，我們報道了僵尸病原體——一種古老的細(xì)菌和病毒，如果它們被埋的永久凍土層隨著地球變暖而解凍，它們可能會從死人身上復(fù)活并威脅人類。接受采訪的科學(xué)家的共識是:這是不可能的——盡管有一個有趣的軼事，說是一位科學(xué)家的膝蓋可能在接觸解凍的海豹后感染了。但我們確實想跟進(jìn)，看看關(guān)于永久凍土層融化的最新研究是怎么說的，并了解到凍土層的消亡帶來的另一個威脅。

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.

對永久凍土層造成問題的不僅僅是溫度的升高。科學(xué)家們正在調(diào)查降雨是否會給北極的永久凍土層帶來嚴(yán)重的問題，并對人類造成影響。

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年以來，阿拉斯加的費(fèi)爾班克斯經(jīng)歷了有記錄以來最潮濕的兩年。2014年夏季降雨量為14.6英寸;這是迄今為止雨水最多的夏天。美國陸軍工程兵團(tuán)的地球化學(xué)家托馬斯·道格拉斯說，這對永久凍土層來說不是一件好事。

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.

永久凍土層——由土壤、巖石甚至骨骼和植物等物質(zhì)完全凍結(jié)的地面——占據(jù)了北半球近四分之一的面積。它的大部分已經(jīng)凍結(jié)了數(shù)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.

根據(jù)道格拉斯7月份發(fā)表在《氣候與大氣科學(xué)》上的最新研究，不斷變暖的氣溫已經(jīng)開始融化永久凍土層，而現(xiàn)在，降雨量的增加似乎正在加劇這個問題。

"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."

道格拉斯說:“總的來說，整個北極地區(qū)的氣候都在變得越來越濕潤。”但費(fèi)爾班克斯地區(qū)的情況尤其如此。2014年和2016年分別是夏季降水量排名第一和第三的年份，這在當(dāng)時是90年來的記錄。打破這樣的記錄真的是獨(dú)一無二的。”

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.

為了弄清楚增加的降雨是如何影響永久凍土層的，道格拉斯和他的團(tuán)隊用五年時間研究了三個永久凍土層。他和他的團(tuán)隊專注于永凍層的“活動性層”，即永凍層的最頂層，在夏季自然解凍，在冬季再次凍結(jié)。

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.

為了研究這一層，他的團(tuán)隊在每年夏末，也就是永久凍土層融化最劇烈的時候，測量了它的深度。他們使用冰霜或解凍探測器進(jìn)行測量。

"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.

道格拉斯解釋說:“我們拿一根有把手的金屬棒，把它往地下推，直到它發(fā)出砰的一聲。”那時他們知道他們已經(jīng)接觸到冰凍的永久凍土層。探針側(cè)面的尺子可以告訴使用者桿子在地下的深度。

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年之間，該團(tuán)隊進(jìn)行了2500次測量，他們開始看到了一個模式。在夏季，雨下得越多，永久凍土的解凍面積就越大。

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.

根據(jù)測量地點(diǎn)的地形，有些地方的解凍情況比其他地方更糟。森林和長滿苔蘚的景觀似乎能保護(hù)永久凍土。在那里，每多下一英寸的雨，永久凍土就會融化四分之一英寸。

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.

但在人類活動改變了土地的地方(比如步道和空地)，解凍情況更糟。每增加一英寸的降雨，研究人員就會看到一英寸的融化。在一個特定地點(diǎn)，永久凍土融化深度從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."

道格拉斯解釋說:“當(dāng)你移除植物時，就像在夏天把冷卻器的蓋子打開一樣。它能讓熱量和水迅速進(jìn)入永久凍土層。”

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.

道格拉斯說，在研究小組的所有研究中，他們最重要的發(fā)現(xiàn)是，變薄的永久凍土似乎正在消失——實際上是在融化。