Estimates of methane emissions from the Southern Ocean from quasi-continuous underway measurements of the partial pressure of methane in surface seawater during the 2012/13 austral summer
Estimates of methane emissions from the Southern Ocean from quasi-continuous underway measurements of the partial pressure of methane in surface seawater during the 2012/13 austral summer
复制标题
2012/13 年南半球夏季期间对表层海水甲烷分压进行准连续测量的南大洋甲烷排放量估算
DOI：
10.1080/16000889.2018.1478594
复制
发表时间：
2018
期刊：
影响因子：
--
通讯作者：
Tsunogai Urumu
中科院分区：
文献类型：
--
作者：
Bui Oanh Thi Ngoc;Kameyama Sohiko;Yoshikawa-Inoue Hisayuki;Ishii Masao;Sasano Daisuke;Uchida Hiroshi;Tsunogai Urumu
我们使用了一个新的正在进行的测量系统，调查甲烷分压（CH 4）在表层海水和上覆空气在南大洋从2012年11月下旬至2013年2月中旬。正在进行的系统包括一个光腔衰荡光谱分析仪和一个双头型平衡器。获得的月平均大气CH 4混合比与陆上基线站记录的结果一致（在5 ppb以内）。海水中CH 4浓度除以与大气CH 4平衡的CH 4浓度，其饱和度（SR，%）在85%~ 185%之间;我们计算出的大部分比值都显示出过饱和状态，但上绕极深水南部界限以南的比值除外。SR在低纬度地区较高，包括次南极锋以北的沿海地区，而在次南极锋和绕极上层深水之间则逐渐单调下降。在极锋以南的高纬度地区，由于上升流和垂直混合的影响，SR下降到100%以下。我们发现了一个很强的线性相关betweenSR和表观氧利用率（AOU）南部的极锋。观察到的SR随着AOU的增加而降低，在高AOU（41 µmol kg−1）和低温（-1.8 °C）下达到85%。根据SR与AOU的线性关系，估算了50°S以南整个南大洋12 - 2月CH 4的气候学海气通量：12月、1月和2月的海气CH 4排放量分别为0.027 Tg yr− 1、0.04 Tg yr− 1和0.019 Tg yr− 1。
We used a new underway measurement system to investigate the partial pressure of methane (CH4) in surface seawater and overlying air in the Southern Ocean from late November 2012 to mid-February 2013. The underway system consisted of a cavity ring-down spectroscopy analyser and a shower-head type equilibrator. The monthly mean atmospheric CH4mixing ratios obtained agreed well (within 5 ppb) with those recorded at onshore baseline stations. CH4saturation ratios (SR, %), defined as CH4concentration in seawater divided by CH4concentration equilibrated with atmospheric CH4, varied between 85 and 185%; most of the ratios we calculated indicated supersaturation, except for those from south of the Southern limit of Upper Circumpolar Deep Water.SRwas higher at the lower latitudes, including coastal areas north of the Sub-Antarctic Front, but decreased gradually and monotonously between the Sub-Antarctic Front and the Upper Circumpolar Deep Water. At high latitudes south of the Polar Front,SRdecreased to below 100% due to the effects of upwelling and vertical mixing. We found a strong linear correlation betweenSRand apparent oxygen utilisation (AOU) south of the Polar Front. ObservedSRdecreased with increasing AOU and reached 85% at high AOU (41 µmol kg−1) and low temperature (–1.8 °C). On the basis of the linear relationship betweenSRand AOU, we evaluated the climatological sea–air flux of CH4from December to February for the entire Southern Ocean south of 50°S: Sea–air CH4emission was estimated to be 0.027 Tg yr−1in December, 0.04 Tg yr−1in January, and 0.019 Tg yr−1in February.