Sulphur hexafluoride as a tracer of biogeochemical and physical processes in an open-ocean iron fertilisation experiment
Sulphur hexafluoride as a tracer of biogeochemical and physical processes in an open-ocean iron fertilisation experiment
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DOI：
10.1016/s0967-0645(98)00022-8
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发表时间：
1998-01-01
影响因子：
3
通讯作者：
Stanton, T
中科院分区：
文献类型：
--
作者：
Law, CS;Watson, AJ;Stanton, T
在赤道太平洋进行的第一次检验铁假设的公海实验是使用示踪气体六氟化硫（SF6）来定位和跟踪施肥的地表水。连续的地面测量表明，SF6斑块在最初的24小时内迅速扩散，从最初的64平方公里的释放面积扩展到214平方公里的总面积，并在接下来的三天内保持相对稳定的大小。SF6数据绘制在拉格朗日参考系的使用drogued GPS浮标发布在补丁的中心。SF6补丁保持连贯性，并表现出缓慢的，反气旋振荡在头四天。浮标在两天内在西北方向的补丁顺风运输，这对未来使用浮标在地表水平流研究的影响。在释放后3-4天，在低盐度锋下俯冲，补丁中心被其SF6信号重新定位在25-30米深度的剩余表面补丁的东部。在实验的剩余时间里，后者迅速向西南方向扩散，而俯冲的斑块保持相对静止。密度校正的SF6剖面被用来计算俯冲事件后整个温跃层的平均垂直涡流扩散率为0.25 cm（2）/s。硝态氮进入混合层的垂直通量为2.5 mmol/m（-2）d（-1），与生产力数据相比，f-比值为0.4。结果表明，SF6是一个成功的水团示踪剂，并强调这种技术的潜力，在现场测量和操纵的开放海洋过程。(C)1998爱思唯尔科技有限公司版权所有。
The first open-ocean experiment to test the iron hypothesis in the equatorial Pacific was undertaken using the tracer gas sulphur hexafluoride (SF6) to locate and track the fertilised surface water. Continuous surface measurements showed that the SF6 patch spread rapidly in the first 24 h, from an initial release area of similar to 64 km(2) to a total area of 214 km(2), and remained relatively constant in size for the following three-day period. SF6 data was mapped in a Lagrangian frame of reference by the use of a drogued GPS buoy released at the centre of the patch. The SF6 patch remained coherent and exhibited a slow, anti-cyclonic oscillation during the first four days. The buoy was transported downwind of the patch in a northwesterly direction within two days, which has implications for the future use of buoys in surface-water advection studies. Following subduction below a low-salinity front 3-4 days after release, the patch centre was relocated by its SF6 signal at a depth of 25-30 m to the east of the residual surface patch. The latter spread rapidly to the southwest during the remainder of the experiment, whilst the subducted patch remained relatively stationary. Density-corrected SF6 profiles were used to calculate a mean vertical eddy diffusivity of 0.25 cm(2)/s across the thermocline following the subduction event. A vertical flux of nitrate of 2.5 mmol/m(-2)d(-1) into the mixed layer was estimated, which implied an f-ratio value of 0.4 on comparison with productivity data. The results demonstrate that SF6 is a successful tracer of water masses, and emphasise the potential of this technique for the in situ measurement and manipulation of open-ocean processes. (C) 1998 Elsevier Science Ltd. All rights reserved.