Methane dynamics in the Weddell Sea determined via stable isotope ratios and CFC‐11
Methane dynamics in the Weddell Sea determined via stable isotope ratios and CFC‐11
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通过稳定同位素比和 CFC-11 确定威德尔海的甲烷动力学
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发表时间：
2004
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影响因子：
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通讯作者：
E. Suess
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文献类型：
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作者：
K. Heeschen;R. Keir;G. Rehder;O. Klatt;E. Suess
通过甲烷（CH4）的分布、其稳定的碳同位素δ13C‐CH4和保守的瞬态示踪剂氯氟烃‐11 （CFC‐11,CCl3F）揭示了控制威德尔海甲烷动力学的物理、化学/生物过程。总的来说，CH4和CFC - 11浓度之间几乎呈线性相关。海气交换是该地区甲烷的主要来源，甲烷的分布主要受地表水和缺乏甲烷的暖深水的混合控制。甲烷氧化对主要两端混合的显著影响仅在威德尔盆地中部深处的威德尔海底水（WSBW）中发现，甲烷的周转时间约为20年。混合也控制了大部分δ13C‐CH4的分布，但在盆地深部的WSBW中出现了比预期更轻的碳同位素比率。从箱形模型模拟来看，这种“异常”似乎是由于甲烷氧化造成的，其动力学同位素分馏率约为1.004。威德尔海和南极绕极流的表层水体甲烷混合比普遍为6% ~ 25%。根据这种欠饱和和模式导出的海气交换率，我们估计在南方秋季，CH4的净吸收量约为- 0.5 μmol m - 2 d - 1。
The physical, chemical/biological processes that control the methane dynamics in the Weddell Sea are revealed by the distributions of methane (CH4), its stable carbon isotope ratio, δ13C‐CH4, and the conservative transient tracer, chlorofluorocarbon‐11 (CFC‐11, CCl3F). In general, a nearly linear correlation between CH4 and CFC‐11 concentrations was observed. Air‐sea exchange is the major source of methane to this region, and the distribution of methane is controlled mainly by mixing between surface water and methane‐poor Warm Deep Water. A significant influence of methane oxidation over the predominant two end‐member mixing was only found in the Weddell Sea Bottom Water (WSBW) of the deep central Weddell Basin, where the turnover time of methane appears to be about 20 years. Mixing also controls most of the δ13C‐CH4 distribution, but lighter than expected carbon isotopic ratios occur in the deep WSBW of the basin. From box model simulations, it appears that this “anomaly” is due to methane oxidation with a low kinetic isotope fractionation of about 1.004. The surface waters in the Weddell Sea and the Antarctic Circumpolar Current showed a general methane undersaturation of 6 to 25% with respect to the atmospheric mixing ratio. From this undersaturation and model‐derived air‐sea exchange rates, we estimate a net uptake of CH4 of roughly −0.5 μmol m−2 d−1 during austral autumn.