Air–sea fluxes of CO 2 and CH 4 from the Penlee Point Atmospheric Observatory on the south-west coast of the UK
Air–sea fluxes of CO 2 and CH 4 from the Penlee Point Atmospheric Observatory on the south-west coast of the UK
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DOI：
10.5194/acp-16-5745-2016
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发表时间：
2016-05
影响因子：
6.3
通讯作者：
Mingxi Yang;T. Bell;Frances E. Hopkins;V. Kitidis;P. Cazenave;P. Nightingale;M. Yelland;R. Pascal;J. Prytherch;I. Brooks;T. Smyth
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文献类型：
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作者：
Mingxi Yang;T. Bell;Frances E. Hopkins;V. Kitidis;P. Cazenave;P. Nightingale;M. Yelland;R. Pascal;J. Prytherch;I. Brooks;T. Smyth
抽象的。我们目前的海气通量的二氧化碳（CO2），甲烷（CH 4），动量，和感热测量涡度协方差法从最近成立的Penlee点大气观测站（PPAO）在英国西南海岸。从西南方向（开阔水域）在三个不同的采样高度（大约高于平均海平面15、18和27米）进行测量，每一个都来自2014-2015年的不同时期。在采样高度≥ 18 m a.m.s.l.时，动量通量和感热通量的测量结果与大洋上的输送率有合理的一致性（平均≤ ± 20%）。这证实了PPAO适用于大陆架区域的海气交换测量。协方差海气CO2通量表现出较高的时间变异性。在这两年，从春季到夏季，CO2的空气到海洋的运输量都有所下降，这与春季浮游植物水华的爆发相吻合。我们报告，据我们所知，第一次成功的涡度相关测量的甲烷排放量从海洋环境。在涨潮期间观测到更高的海-气CH 4通量（在15、18、27 m a.m.s.l.时为20 ± 3; 38 ± 3; 29 ± 6 µmole m−2 d−1）。而在落潮期间（14 ± 2; 22 ± 2; 21 ± 5 µmole m−2 d−1），这与当地潮汐环流驱动的河口外流导致的CH 4源升高一致。这些通量比预测的开阔海洋CH 4排放量高出几倍，但大大低于其他水生CH 4热点（如极地、淡水）的估计值。最后，我们发现涡动协方差法对海气CH 4通量的探测极限为每小时20 μmole m−2 d−1（24小时4 μmole m−2 d−1）。
Abstract. We present air–sea fluxes of carbon dioxide (CO2), methane (CH4), momentum, and sensible heat measured by the eddy covariance method from the recently established Penlee Point Atmospheric Observatory (PPAO) on the south-west coast of the United Kingdom. Measurements from the south-westerly direction (open water sector) were made at three different sampling heights (approximately 15, 18, and 27 m above mean sea level, a.m.s.l.), each from a different period during 2014–2015. At sampling heights ≥ 18 m a.m.s.l., measured fluxes of momentum and sensible heat demonstrate reasonable ( ≤ ±20 % in the mean) agreement with transfer rates over the open ocean. This confirms the suitability of PPAO for air–sea exchange measurements in shelf regions. Covariance air–sea CO2 fluxes demonstrate high temporal variability. Air-to-sea transport of CO2 declined from spring to summer in both years, coinciding with the breakdown of the spring phytoplankton bloom. We report, to the best of our knowledge, the first successful eddy covariance measurements of CH4 emissions from a marine environment. Higher sea-to-air CH4 fluxes were observed during rising tides (20 ± 3; 38 ± 3; 29 ± 6 µmole m−2 d−1 at 15, 18, 27 m a.m.s.l.) than during falling tides (14 ± 2; 22 ± 2; 21 ± 5 µmole m−2 d−1), consistent with an elevated CH4 source from an estuarine outflow driven by local tidal circulation. These fluxes are a few times higher than the predicted CH4 emissions over the open ocean and are significantly lower than estimates from other aquatic CH4 hotspots (e.g. polar regions, freshwater). Finally, we found the detection limit of the air–sea CH4 flux by eddy covariance to be 20 µmole m−2 d−1 over hourly timescales (4 µmole m−2 d−1 over 24 h).