Physical mixing effects on iron biogeochemical cycling: FeCycle experiment
Physical mixing effects on iron biogeochemical cycling: FeCycle experiment
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DOI：
10.1029/2006jc003748
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发表时间：
2007-06-20
影响因子：
3.6
通讯作者：
Boyd, P. W.
中科院分区：
文献类型：
--
作者：
Croot, P. L.;Frew, R. D.;Boyd, P. W.
[0]在2003年2月（南夏）对新西兰东南部进行的中尺度SF6示踪剂释放FeCycle中，评估了物理过程对高营养低叶绿素（HNLC）地区铁的分布、形态和来源/汇的影响。在FeCycle期间，物理混合过程普遍存在，斑块快速生长（应变速率gamma = 0.17 - 0.20 d(-1)），从圆形（50 km(2)）到第10天，形成类似400 km(2)的长丝。层与层之间的滑动导致补丁头覆盖在未注入的水上，而尾部被相邻的地表水覆盖，导致深度SF6最大值。随着斑块的发展，它携带了含有较高叶绿素浓度的邻近水域，但溶解铁（DFe）水平与最初注入的斑块相似。在FeCycle循环中，地表水的DFe含量较低，约为60 pmol L-1，以有机络合为主。夜间铁（II）的测量值接近20 pmol L-1，表明在没有可识别的快速铁（III）还原过程的情况下存在铁（II）有机配合物。结合停留时间和浮游植物对DFe的吸收通量，它在离开冬季混合层（WML）之前在生物群中循环140 - 280次。这种强烈的铁需求，加上低于铁线的低铁：NO3- (11.9 μ mol: mol)，表明铁的垂直扩散不足以缓解慢性铁限制，表明大气输入铁对该地区的重要性。
[1] The effects of physical processes on the distribution, speciation, and sources/sinks for Fe in a high-nutrient low-chlorophyll (HNLC) region were assessed during FeCycle, a mesoscale SF6 tracer release during February 2003 ( austral summer) to the SE of New Zealand. Physical mixing processes were prevalent during FeCycle with rapid patch growth ( strain rate gamma = 0.17 - 0.20 d(-1)) from a circular shape (50 km(2)) into a long filament of similar to 400 km(2) by day 10. Slippage between layers saw the patch-head overlying noninfused waters while the tail was capped by adjacent surface waters resulting in a SF6 maximum at depth. As the patch developed it entrained adjacent waters containing higher chlorophyll concentrations, but similar dissolved iron (DFe) levels, than the initial infused patch. DFe was low similar to 60 pmol L-1 in surface waters during FeCycle and was dominated by organic complexation. Nighttime measurements of Fe(II) similar to 20 pmol L-1 suggest the presence of Fe( II) organic complexes in the absence of an identifiable fast Fe(III) reduction process. Combining residence times and phytoplankton uptake fluxes for DFe it is cycled through the biota 140 - 280 times before leaving the winter mixed layer (WML). This strong Fe demand throughout the euphotic zone coupled with the low Fe: NO3- (11.9 mu mol: mol) below the ferricline suggests that vertical diffusion of Fe is insufficient to relieve chronic iron limitation, indicating the importance of atmospheric inputs of Fe to this region.