Nature · 人与自然 / 气候 / 生态 / 科普
冻土苏醒：北极永久冻土融化，正把封存万年的"古碳"释放进海洋
A sweeping new study finds the Arctic's thawing permafrost is flushing ancient carbon into rivers and the ocean, where long-dormant microbes can turn it into greenhouse gases that push warming further
中文导读
北极的表层植被之下，埋藏着地球上规模最大的碳库之一——数十万年来被封存在永久冻土里的古碳，其总量约为当前大气中碳含量的两倍。如今，这份"冰冻遗产"正在苏醒。最新一项综合研究警告：永久冻土正以前所未有的速度融化，把大量远古碳冲入河流与海洋；长期休眠的微生物随之"复活"，把碳分解成二氧化碳与甲烷，反过来加速气候变暖。这一"融化—释放—再变暖"的正反馈循环，被科学家视为未来气候预测中最大的不确定因素。本文沿"封存—融化—唤醒—反馈"的机制链，揭示北极冻土如何在不知不觉中，成为悬在气候系统上的一颗定时炸弹。
一、原文精读
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【1】Beneath a thin layer of vegetation, the Arctic holds one of the planet's largest stores of carbon — frozen, quiet, and, until recently, safely sealed away. Roughly twice as much carbon as now circulates in the atmosphere lies locked in permafrost, the perennially frozen ground that has kept it inert for tens of thousands of years.
【2】A sweeping new study, published this month, warns that this frozen vault is now thawing fast enough to reshape Arctic rivers and release vast quantities of ancient carbon into the ocean. Led by an international team of climate scientists, the work combined satellite records, river-water sampling and laboratory incubations to trace the journey of carbon from thawing soil to the sea.
【3】The mechanism is at once simple and unsettling. As ground that has been frozen since the last ice age thaws, long-dormant microbes wake and begin to decompose the organic matter they find, respiring carbon dioxide and methane into the atmosphere and leaching dissolved carbon into streams.
【4】Satellite measurements suggest the permafrost region now loses more carbon each year than it absorbs, a reversal that has turned the Arctic from a carbon sink into a net source. Field data from Siberian and Alaskan sites show thaw depths increasing year on year, exposing soils that had been sealed for millennia.
【5】Worse, the process feeds on itself. The greenhouse gases it emits warm the planet further, which melts more permafrost, which in turn releases more gas — a positive feedback loop that no model yet captures with confidence.
【6】"We are essentially turning on a heater that has been off for millennia, and the thermostat is no longer in our hands," one of the study's lead authors observed. The team estimates that permafrost emissions could rival those of a major industrial nation by mid-century, though the exact magnitude remains fiercely debated.
【7】The researchers are careful to stress the limits of their evidence. Much of the carbon flushed into rivers may be buried again in coastal sediments before it ever reaches the atmosphere, and not every thawed gram of carbon is immediately decomposed.
【8】Even so, the implications are difficult to overstate. A feedback that accelerates beyond human control would undercut every effort to curb emissions elsewhere, which is why the team urges that permafrost be treated not as a distant curiosity but as a front-line component of climate policy.
【9】For a public often focused on cars and factories, the message is humbling: some of the most consequential carbon on Earth is not burned but simply thawed. Watching the frozen ground wake, scientists argue, is no longer a matter of curiosity but of urgency — a reminder that the quietest processes can carry the loudest consequences.
原文出处：本文根据 ScienceDaily 报道《Thawing permafrost releases ancient carbon into the ocean》（2026-10-03）及 Nature、phys.org 相关永久冻土碳循环研究（2026-08 至 09 月）综合整理改写，供学习使用。
三、长难句分析（三步拆解法）
Roughly twice as much carbon as now circulates in the atmosphere lies locked in permafrost, the perennially frozen ground that has kept it inert for tens of thousands of years.
主干：twice as much carbon ... lies locked in permafrost（主语 + lies + 过去分词 locked 表状态）
比较状语从句：as now circulates in the atmosphere（"如同现在大气中循环的那样多"，修饰 twice as much carbon）
同位语：the perennially frozen ground（解释 permafrost）
定语从句：that has kept it inert（修饰 ground，it 指代 carbon）
考点：twice as much ... as ... 倍数比较结构；过去分词 locked 作状语；同位语；that 定语从句
译文：封存在永久冻土中的碳，大约是当前在大气中循环的碳的两倍——这片常年冻结的土地使这些碳在数万年里一直保持惰性。
Led by an international team of climate scientists, the work combined satellite records, river-water sampling and laboratory incubations to trace the journey of carbon from thawing soil to the sea.
主干：the work combined A, B and C（主语 + combined + 三个并列宾语）
过去分词作状语：Led by an international team of climate scientists（"由……率领"）
不定式作目的状语：to trace the journey of carbon from thawing soil to the sea
考点：过去分词作状语；不定式作目的状语；并列宾语
译文：这项研究由国际气候科学家团队牵头，综合了卫星记录、河流水样采集与实验室培养实验，以追踪碳从解冻土壤到海洋的旅程。
As ground that has been frozen since the last ice age thaws, long-dormant microbes wake and begin to decompose the organic matter they find, respiring carbon dioxide and methane into the atmosphere and leaching dissolved carbon into streams.
主干：long-dormant microbes wake and begin to decompose the organic matter（主语 + 并列谓语 wake and begin）
时间状语从句：As ground ... thaws（"随着……解冻"）
定语从句：that has been frozen since the last ice age（修饰 ground）
定语从句（省略 that）：they find（修饰 matter）
现在分词作伴随/结果状语：respiring ... and leaching ...（respire A into B；leach C into D）
考点：As 时间状语从句；that 定语从句；省略关系词的定语从句；现在分词作状语
译文：随着自上一个冰河时代以来一直被冻结的土地解冻，长期休眠的微生物苏醒过来，开始分解它们找到的有机物，把二氧化碳和甲烷呼入大气，并把溶解的碳渗滤进溪流。
The greenhouse gases it emits warm the planet further, which melts more permafrost, which in turn releases more gas — a positive feedback loop that no model yet captures with confidence.
主干：The greenhouse gases ... warm the planet further（主语 + warm + 宾语 + 补语）
定语从句（省略 that）：it emits（修饰 gases）
非限制性定语从句（连锁）：which melts more permafrost ... which in turn releases more gas（两个 which 依次指代前面整个主句/从句）
同位语 + 定语从句：a positive feedback loop that no model yet captures with confidence
考点：省略关系词的定语从句；which 引导非限制性定语从句指代整个主句；同位语
译文：冻土排放出的温室气体使地球进一步变暖，这又使更多永久冻土融化，进而释放出更多气体——这是一个任何模型都还无法准确捕捉的正反馈循环。
A feedback that accelerates beyond human control would undercut every effort to curb emissions elsewhere, which is why the team urges that permafrost be treated not as a distant curiosity but as a front-line component of climate policy.
主干：A feedback ... would undercut every effort to curb emissions elsewhere（主语 + would undercut + 宾语）
定语从句：that accelerates beyond human control（修饰 feedback）
非限制性定语从句：which is why ...（which 指代前面整个主句）
表语从句：why the team urges that ...
宾语从句（虚拟语气）：permafrost (should) be treated ...（urge 后接 that + (should) + 动词原形）
并列结构：not as a distant curiosity but as a front-line component（not ... but ...）
考点：定语从句；which 指代整个主句；urge that ... (should) do 虚拟语气；not ... but ... 并列结构
译文：一个超出人类控制的反馈会削弱其他地方抑制排放的一切努力，这正是研究团队敦促把永久冻土视为气候政策前沿组成部分、而非遥远奇闻的原因。
四、全文大意
在北极薄薄的植被之下，埋藏着地球上规模最大的碳库之一：永久冻土中封存的碳，约为当前大气中碳含量的两倍，数十万年来一直保持惰性、被冰雪密封。然而，这份"冰冻遗产"正在苏醒。本月发表的一项综合研究警告，永久冻土正以前所未有的速度融化，足以重塑北极河流，并把大量远古碳释放进海洋。该研究由国际气候科学家团队牵头，综合卫星记录、河流水样采集与实验室培养实验，追踪碳从解冻土壤到海洋的旅程。其机理既简单又令人不安：随着自上一个冰河时代以来一直被冻结的土地解冻，长期休眠的微生物苏醒，分解有机物，把二氧化碳与甲烷呼入大气，并把溶解的碳渗滤进溪流。卫星数据显示，冻土区每年流失的碳已超过其吸收量，这一逆转使北极从"碳汇"变成了"净排放源"；西伯利亚与阿拉斯加的野外观测也显示解冻深度逐年增加。更糟的是，这一过程会自我强化：排放的气体使地球进一步变暖，融化更多冻土，释放更多气体，形成一个任何模型都还无法准确捕捉的正反馈循环。一位主要作者形容："我们实质上是在开启一台停用了数千年的加热器，而温控器已不再掌握在我们手中。"研究团队估计，到本世纪中叶，永久冻土的排放量或可匹敌一个主要工业国，尽管其确切规模仍争议激烈。当然，研究者也谨慎指出证据的局限：冲入河流的碳可能在海床沉积物中被重新掩埋，未必全部进入大气，各站点的相关性也尚不能拼成可靠的全球预算。即便如此，其影响仍难以低估：一个失控的反馈会削弱其他所有减排努力，因此研究团队呼吁，把永久冻土从"遥远的奇闻"提升为气候政策的前沿组成部分。对习惯了关注汽车与工厂的公众而言，这一发现令人警醒：地球上一些影响最深远的碳，并非被"燃烧"掉，而只是被"融化"了出来。科学家指出，注视冻土苏醒，已不再是好奇，而是迫在眉睫的紧迫——最安静的进程，往往带来最响亮的后果。
五、思考与仿写
思考题：结合第 4、5 段，为什么北极由"碳汇"变成"净排放源"会形成一个"正反馈循环"？这一循环为什么被科学家称为气候预测中"最大的不确定因素"？
仿写题：仿照第 9 段 "some of the most consequential carbon on Earth is not burned but simply thawed."（"not A but B" 并列结构 + 过去分词）的句式，围绕「低碳出行」「节约资源」或「保护环境」写一个句子。