Fluxes and fate of dissolved methane released at the seafloor at the landward limit of the gas hydrate stability zone offshore western Svalbard
Fluxes and fate of dissolved methane released at the seafloor at the landward limit of the gas hydrate stability zone offshore western Svalbard
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DOI：
10.1002/2015jc011084
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发表时间：
2015-09-01
影响因子：
3.6
通讯作者：
James, Rachael H.
中科院分区：
文献类型：
--
作者：
Graves, Carolyn A.;Steinle, Lea;James, Rachael H.
甲烷从海底沉积物的广泛渗入近海的svalbard靠近气体水合物稳定区（GHSZ）的地下限制，部分可能是由于底部水变暖而导致的水合不稳定驱动。为了评估这种甲烷是否到达可能有助于进一步变暖的大气中，我们已经对海水和上斜坡和架子区域的空气进行了全面的调查。在GHSZ限制的附近，大约在400 m的水深下，甲烷浓度靠近海床，达到825 nm。通过水平和垂直混合以及微生物介导的氧化从底部水中溶解的简单盒子模型，表明在海底释放的甲烷的大约60％在深度氧化之前，在与上面的地表水混合之前。因此，深水不是中间水和地表水的重要来源。相反，这些水域中相对较高的甲烷浓度（最高50 nm）归因于等轴湍流与架子水的混合。在架子上，广泛的海底渗漏
Widespread seepage of methane from seafloor sediments offshore Svalbard close to the landward limit of the gas hydrate stability zone (GHSZ) may, in part, be driven by hydrate destabilization due to bottom water warming. To assess whether this methane reaches the atmosphere where it may contribute to further warming, we have undertaken comprehensive surveys of methane in seawater and air on the upper slope and shelf region. Near the GHSZ limit at approximate to 400 m water depth, methane concentrations are highest close to the seabed, reaching 825 nM. A simple box model of dissolved methane removal from bottom waters by horizontal and vertical mixing and microbially mediated oxidation indicates that approximate to 60% of methane released at the seafloor is oxidized at depth before it mixes with overlying surface waters. Deep waters are therefore not a significant source of methane to intermediate and surface waters; rather, relatively high methane concentrations in these waters (up to 50 nM) are attributed to isopycnal turbulent mixing with shelf waters. On the shelf, extensive seafloor seepage at