读英语文章 地磁危机

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2024年4月26日发(作者：)

February 22,2021(Science News)

A magnetic field reversal 42,000 years ago may have contributed

to mass extinctions

4万2千年前的磁场逆转可能导致了大灭绝

A flip-flop of Earth’s magnetic poles between 42,000 and

41,000 years ago briefly but dramatically shrank the magnetic

field’s strength — and may have triggered a cascade of

environmental crises on Earth, a new study suggests.

一项新的研究表明，在42000年到41000年前，地球磁极的一次

巨变短暂但戏剧性地缩小了磁场的强度，并可能在地球上引发了一连

串的环境危机。

With the help of new, precise carbon dating obtained from

ancient tree fossils, the researchers correlated shifts in

climate patterns, large mammal extinctions and even changes in

human behavior just before and during the Laschamps excursion,

a brief reversal of the magnetic poles that lasted less than

a thousand years. It’s the first study to directly link a

magnetic pole reversal to large-scale environmental changes,

the team reports in the Feb. 19 Science.

在从古树化石中获得的新的、精确的碳定年法的帮助下，研究人

员将气候模式的变化、大型哺乳动物的灭绝，甚至人类行为在

Laschamps(持续了不到1000年的磁极短暂逆转)之前和期间的变化

联系起来。该研究小组在2月19日的《科学》杂志上报道说，这是

第一个将磁极逆转与大规模环境变化直接联系起来的研究。

During a reversal, Earth’s protective magnetic field, which

shields the planet from a barrage of charged particles

streaming from the sun, can lose strength. So some researchers

have suggested that these flip-flops may be linked to

extinction events.

在逆转过程中，地球的保护性磁场（它保护地球免受来自太阳的

带电粒子流的密集攻击）会失去强度。因此，一些研究人员认为，这

种逆转可能与物种灭绝事件有关。

But evidence for this has proven elusive. In fact, “the general

belief had been that geomagnetic changes had no impact on

climate or anything else,” says Alan Cooper, an evolutionary

biologist at BlueSky Genetics in Adelaide. One reason for that

belief is a dearth of precise dates for the timing and duration

of the geomagnetic event to correlate with environmental, ice

core and magnetic rock records.

但这方面的证据难以找到。事实上，“人们普遍认为地磁变化对

气候或其他任何事情都没有影响，”阿德莱德蓝天基因公司的进化生

物学家艾伦·库珀说。这种看法的一个原因是缺乏与环境、冰芯和磁

性岩石记录相关联的地磁事件的时间和持续时间的精确日期。

Enter New Zealand’s kauri tree, among the most ancient in the

world. The country’s swampy bogs preserve the relics of kauri

trees dating as far back as the Laschamps excursion. Cooper and

his colleagues obtained cross-sections from four ancient trees

recovered from a swamp at Ng­āwhā Springs in northern New

Zealand, and analyzed them for carbon-14, a radioactive form

of carbon.

新西兰贝壳杉，世界上最古老的树之一。这个国家的沼泽保存着

贝壳杉树的遗迹，可以追溯到Laschamps之旅。Cooper和他的同事

从新西兰北部Ng -āwhā Springs的沼泽中提取了四棵古树的横截面，

并对它们进行了碳-14(一种放射性碳)的分析。

In particular, one massive preserved log dating to about 41,000

years ago offered up a 1,700-year-long carbon-14 record. That

record revealed major changes in carbon-14 during the time

period running up to and including the excursion, the team

reports. That makes sense: Increasing incoming cosmic rays —

as would occur with a weakened magnetic field — also produce

more carbon-14 in the atmosphere, a carbon signature which

would then become incorporated into the tree’s tissues.

尤其值得注意的是， 这些大约41000年前的古数记录了1700年

间的碳-14记录。研究小组报告说，这一记录揭示了碳-14在

Laschamps的大迁徙之前以及包括那次迁徙在内的这段时间内的主要

变化。这是有道理的:随着磁场减弱，越来越多进入大气层的宇宙射

线也会产生更多的碳-14，这是一种碳特征，然后会被吸收到树的组

织中。

The team simulated how a weakened magnetic field might alter

atmospheric weather patterns. The computer analysis suggested

that the increase of charged particles entering the atmosphere

would also increase the production of atmospheric hydrogen and

nitrogen oxides — molecules that tend to consume ozone. That

would reduce the ability of stratospheric ozone to shield

Earth’s denizens from ultraviolet radiation. The atmospheric

changes would also affect how much sunlight is absorbed at

different layers in the atmosphere, leading to large-scale

changes in weather patterns that would have cooled the planet.

该小组模拟了减弱的磁场如何改变大气天气模式。计算机分析表

明，进入大气的带电粒子的增加也会增加大气中氢和氮氧化物的产生，

这些分子往往会消耗臭氧。这将降低平流层臭氧保护地球居民免受紫

外线辐射的能力。大气变化也会影响到大气中不同层吸收阳光的量，

导致大规模的天气模式变化，从而使地球变冷。

本文标签： 地球大气磁场变化研究