Rethinking the global carbon cycle with a large, dynamic and microbially mediated gas hydrate capacitor
Rethinking the global carbon cycle with a large, dynamic and microbially mediated gas hydrate capacitor
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DOI：
10.1016/s0012-821x(03)00325-x
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发表时间：
2003-08-25
影响因子：
5.3
通讯作者：
Dickens, GR
中科院分区：
文献类型：
--
作者：
Dickens, GR
显著的负Δ（13）C漂移表征了过去几个环境突变（< 100 kyr）的间隔。这些异常，最好的例子是在古新世/始新世热最高峰（PETM）约2.5ppm的下降。55.5马，引起我们的注意，因为他们缺乏对全球碳循环的传统模型的解释。越来越多的地球科学家认为，它们意味着海洋天然气水合物大量释放甲烷，尽管通常没有考虑这种解释的潜在过程或随之而来的后果。在最基本的层面上，一个大型的动态“天然气水合物电容器”以与深海温度等外部条件相关的速率储存和释放C-13耗尽的碳。电容器包含三个内部储层：溶解气体、气体水合物和游离气体。碳通过微生物分解有机质、浅层沉积物中甲烷的厌氧氧化和海底气体排放进入和离开这些储层;碳通过几个过程在这些储层之间循环，包括流体流动、天然气水合物的沉淀和溶解以及埋藏。数值模拟表明，简单的天然气水合物电容器驱动的推断变化，在最早期的底层水变暖，可以产生一个全球VC漂移，模仿的意见。同样的模型在更长的时间内扩展表明，可变的CH 4通量和天然气水合物可以部分解释其他三角洲（13）C的偏移，快速和缓慢，大和小，负和正。虽然这种建模是基本的（因为现代和古代天然气水合物系统的过程和变量仍然受到很好的约束），接受一个巨大的，外部监管的天然气水合物电容器迫使我们重新思考VC记录和全球碳循环的运作。(C)2003 Elsevier B. V.保留所有权利。
Prominent negative delta(13)C excursions characterize several past intervals of abrupt ( < 100 kyr) environmental change. These anomalies, best exemplified by the > 2.5parts per thousand drop across the Paleocene/Eocene thermal maximum (PETM) ca. 55.5 Ma, command our attention because they lack explanation with conventional models for global carbon cycling. Increasingly, Earth scientists have argued that they signify massive release Of CH4 from marine gas hydrates, although typically without considering the underlying process or the ensuing ramifications of such an interpretation. At the most basic level, a large, dynamic 'gas hydrate capacitor' stores and releases C-13-depleted carbon at rates linked to external conditions such as deep ocean temperature. The capacitor contains three internal reservoirs: dissolved gas, gas hydrate, and free gas. Carbon enters and leaves these reservoirs through microbial decomposition of organic matter, anaerobic oxidation of CH4 in shallow sediment, and seafloor gas venting; carbon cycles between these reservoirs through several processes, including fluid flow, precipitation and dissolution of gas hydrate, and burial. Numerical simulations show that simple gas hydrate capacitors driven by inferred changes in bottom water warming during the PETM can generate a global VC excursion that mimics observations. The same modeling extended over longer time demonstrates that variable CH4 fluxes to and from gas hydrates can partly explain other delta(13)C excursions, rapid and slow, large and small, negative and positive. Although such modeling is rudimentary (because processes and variables in modern and ancient gas hydrate systems remain poorly constrained), acceptance of a vast, externally regulated gas hydrate capacitor forces us to rethink VC records and the operation of the global carbon cycle throughout time. (C) 2003 Elsevier B.V. All rights reserved.