海平面下降造成火山溢流

原文網址：https://goo.gl/fDgHBV

海平面下降造成火山溢流

一組國際研究團隊發現了固體地球和氣候系統之間的新關聯

在整部漫長的地球歷史中，氣候變遷的某些規律是有跡可循的。其中一例便是全球平均溫度跟大氣二氧化碳濃度通常是攜手併行的。簡單來說，當氣溫下降時二氧化碳濃度也會跟著下降，反之亦然。

然而，事情總有例外。由德國亥姆霍茲基爾海洋研究中心(GEOMAR)與德國艾佛瑞德維根納極地海洋研究所領導的國際科學家團隊，近日發現了這些例外的可能成因。其中一個例子發生在地球最近一次進入冰河期的時候。在大約80000年前氣溫下降的時候，大氣中的二氧化碳含量卻依然維持在相對穩定的狀態長達數千年。今日刊登在期刊《自然通訊》(Nature Communications)的研究，認為原因可能是海平面下降造成海底火山變得更加活躍。

在冰河期狀態成形的期間，溫度下降和冰層擴張會造成海水重新分配至陸地區域。海平面因此下降，海床和地殼內部受到的壓力跟著減少，使得岩漿的產量上升。

本研究的主要作者Jörg Hasenclever博士解說團隊使用的方法：「為了更加瞭解並且定量化此過程，我們結合了各項地球動力學數據來建構出一個涵蓋各方面的電腦模型。除此之外，我們也分析了古氣候數據並且利用全球碳循環模型來進行模擬。」研究探討中洋脊和43座洋島火山如何隨著冰河期的海平面變化而做出反應。

GEOMAR的教授Lars Rüpke博士補充：「我們的研究方法顯示海床受到的壓力減少引起火山排出更多的岩漿以及二氧化碳。在氣候系統逐漸降溫至末次冰河期期間，火山排放二氧化碳的速率增加可能穩定了大氣的二氧化碳濃度。」

研究指出在5000年至15000年這種相對短期的地質尺度下，固體地球和氣候系統之間的緊密互動關係依然存在。共同作者，艾佛瑞德維根納研究所的Gregor Knorr博士對此解釋：「這類互動關係對地球系統的研究引入了新要素，使我們可以更加瞭解冰河期造成海平面變動時氣候會如何演化。」

Falling Sea Level caused Volcanos to Overflow

A Team of international researches found new connections between the solid earth and the climate system

Climate evolution shows some regularities, which can be traced throughout long periods of earth’s history. One of them is that the global average temperature and the carbon dioxide concentration in the atmosphere usually go hand-in-hand. To put it simple: If the temperatures decline, the CO2 values also decrease and vice versa.

However, there are exceptions. An international team of scientists led by the GEOMAR Helmholtz Centre for Ocean Research Kiel and the Alfred-Wegener-Institute Helmholtz Centre for Polar and Marine Research has now discovered a possible cause for such irregularities. An example is the last transition to glacial conditions. At approximately 80,000 years ago the temperatures declined, but the amount of carbon dioxide in the atmosphere remained relatively stable for several thousand years. The reason for this could be enhanced volcanic activity in the oceans induced by a falling sea level. The study is being published today in the journal Nature Communications. 

During the development of glacial conditions temperatures decrease and ice sheets form, resulting in the redistribution of water from the ocean to continental regions. Thus, the sea level falls and the pressure on the on the seabed and thereby in the earth's crust decreases, which enhances magma production. 

“To better understand and quantify these processes, we developed a comprehensive computer model that we integrated with geodynamic data. In addition to this we analyzed paleo-climate data and carried out simulations with a model of the global carbon cycle,“ Dr. Jörg Hasenclever, the lead author of the study explains the approach of the team. The study investigated the response of mid-ocean ridges and of 43 ocean island volcanoes to glacial sea level changes.

“Our approach has shown that the decreasing pressure at the seafloor could have induced increased lava- and carbon dioxide emissions. The enhanced volcanic carbon dioxide flux may have stabilized the atmospheric carbon dioxide concentrations during the climate system’s descent into the last ice age“, adds Prof. Dr. Lars Rüpke of GEOMAR.

The investigations suggest that close interactions between the solid earth and the climate system exist also on geologically relatively short time scales of about 5,000 to 15,000 years. Co-author Dr. Gregor Knorr of the Alfred-Wegener-Institute further explains: “Such interactions could provide a novel component for earth system research to better understand the climate evolution at times of glacial sea level changes.”

原始論文：Jörg Hasenclever, Gregor Knorr, Lars H. Rüpke, Peter Köhler, Jason Morgan, Kristin Garofalo, Stephen Barker, Gerrit Lohmann, Ian R. Hall. Sea level fall during glaciation stabilized atmospheric CO2 by enhanced volcanic degassing. Nature Communications, 2017; 8: 15867 DOI: 10.1038/NCOMMS15867

引用自：Helmholtz Centre for Ocean Research Kiel (GEOMAR). "Falling sea level caused volcanoes to overflow: New connections between the solid earth and the climate system."