原文網址：http://news.fsu.edu/news/2017/08/01/fsu-research-chemical-weathering-alleviate-climate-change-effects/
化學風化可以減輕氣候變遷帶來的一部份影響
Kathleen Haughney
科學家試著瞭解跟氣候變遷有關的影響和作用時，也為不久之後的未來帶來了一些好消息。
在化學風化作用中，二氧化碳分解岩石後會被封存在沉積物內部。美國佛羅里達州立大學的科學家團隊發現化學風化可以比過往研究推估快上許多的速率進行，或許能抵銷人類現在和未來造成氣候變遷的一部份。
科學家一般認為這種作用進行的速率慢得出奇，要花上數十萬年至數百萬年來幫助減緩暖化的趨勢。
佛羅里達大學的研究人員提出化學風化可能不用花上數百萬年，只需要數萬年就能作用。
但它仍然不是一種救急之道。
此篇論文的主要研究人員，佛羅里達州立大學的博士後研究員和國家高磁場研究室的Theodore Them表示：「化學風化增強是地球對二氧化碳濃度升高的自然反應之一。好消息是此作用可以幫助平衡燃燒化石燃料、除林和農業活動帶來的影響。壞消息是它至少得用上數萬年，才能開始抵銷大氣中由人類所排放的過量二氧化碳。」
隨著大氣二氧化碳濃度提高，氣候也變得更加溫暖。較暖的氣候會加速化學風化作用進行，消耗大氣中的二氧化碳並減緩溫室效應，因而造成氣候冷化。
為了進行這項研究，研究人員測定了地球史上一段迅速暖化的時期中，岩石受到化學作用分解的速率。該時期為大約1億8300萬年前侏儸紀早期發生的生物大滅絕事件，稱作托阿爾階海洋缺氧事件(Toarcian Oceanic Anoxic Event)。
研究人員跟英國杜倫大學的科學家合作，利用國家磁場實驗室地球化學小組的尖端分析儀器來處理並測量岩石樣品中的稀有元素。
Them表示：「我們注意到雖然在那段時期化學風化作用的速率大為增加，但沒有跟先前對此事件的假設一樣高。然而，真正令人驚訝的是地球竟然能在如此短時間內就對環境變遷做出反應。」
但化學風化作用增強也有另一項負面效應。
研究人員的發現提出侏儸紀早期海洋出現大範圍缺氧區域，是因為岩石分解產生了過量營養鹽流入海洋的緣故。
研究人員推測未來因地球暖化導致的氣候變遷和氣象模式變化，將會造成降雨量增加而讓更多河水和營養鹽運輸到海岸地區。他們預期這會讓未來海岸地區的海水缺氧事件規模和持續時間都變得更強，而對該區域的海洋生物造成負面影響。
論文共同作者，佛羅里達州立大學的地質學助理教授Jeremy
Owens表示：「像這樣能讓我們瞭解古代氣候變遷的研究，有助於我們推估它們發生的時間、事件內容和環境因應產生的變化，而可以對未來氣候的樣貌做出更準確的預測。」
Chemical weathering could
alleviate some climate change effects
There could
be some good news on the horizon as scientists try to understand the effects
and processes related to climate change.
A team of Florida State University scientists has
discovered that chemical weathering,
a process in which carbon dioxide breaks down rocks and then gets trapped in
sediment, can happen at a much faster rate than scientists previously assumed
and could potentially counteract some of the current and future climate change
caused by humans.
The findings were published in the
journal Scientific Reports.
Scientists have generally
thought that this process takes hundreds of thousands to millions of years to
occur, helping to alleviate warming trends at an exceptionally slow rate.
Rather than potentially millions of
years, FSU researchers now suggest it can take several tens of thousands of
years.
It’s not a quick fix
though.
“Increased chemical weathering is one
of Earth’s natural responses to carbon dioxide increases,” said Theodore Them,
the lead researcher on the paper and a postdoctoral researcher at Florida State
and the National High Magnetic Field Laboratory. “The good news is that this
process can help balance the effects of fossil fuel combustion, deforestation
and agricultural practices. The bad news is that it will not begin to
counteract the excessive amounts of atmospheric carbon dioxide that humans are
emitting for at least several thousand years.”
As atmospheric carbon dioxide
concentrations increase, the climate gets warmer. The warmer climate speeds up
chemical weathering, which consumes carbon dioxide from the atmosphere and
mitigates the greenhouse effect, thus leading to climate cooling.
To conduct the study, the research team
determined the rate at which rocks were chemically broken down over a period of
rapid warming in the Early Jurassic Epoch called the Toarcian Oceanic Anoxic
Event, an interval where a major extinction event occurred about 183 million
years ago.
Working with colleagues at Durham
University in the United Kingdom and using state-of-the-art analytical
instrumentation within the National MagLab’s Geochemistry
Group, the researchers processed and measured the trace elements of
their rock samples.
“We noticed that although chemical
weathering increased significantly during this time interval, it was not as
large as previously hypothesized for this event,” Them said. “What’s really
striking, however, is the planet’s ability to respond to these environmental
changes on such short timescales.”
This increased chemical weathering
process could have another downside.
The researchers’ findings suggest that
widespread oxygen-deficient oceans occurred because an excess of nutrients from
the breakdown of rocks flowed into the oceans during the Early Jurassic Period.
The researchers predict that future
changes in climate and weather patterns due to a warming planet will create
more precipitation and increase the amount of river water and nutrients
transported to coastal regions. This is expected to increase both the size and
duration of future coastal ocean deoxygenation, negatively impacting sea life
in those areas.
“Understanding ancient climatic change
like this helps us anticipate the timing, implications, and environmental
response to better predict future climate scenarios,” said FSU Assistant
Professor of Geology Jeremy Owens, a co-author on the paper.
原始論文：Theodore
R. Them, Benjamin C. Gill, David Selby, Darren R. Gröcke, Richard M.
Friedman, Jeremy D. Owens. Evidence for rapid weathering response to
climatic warming during the Toarcian Oceanic Anoxic Event. Scientific
Reports, 2017; 7 (1) DOI: 10.1038/s41598-017-05307-y
引用自：Florida State University. "Chemical weathering could
alleviate some climate change effects." ScienceDaily. ScienceDaily, 1
August 2017.
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