Observational research for iron, biological productivity, and carbon cycle in the subarctic northwestern Pacific

2003 - 2006年对西北太平洋亚北极地区铁元素的二维分布进行了高时空分辨率的研究。结果表明：1)盐盐混合层中溶解铁（DFe）的月平均浓度变化与硝态氮的月平均浓度变化呈平行关系，其最大值出现在科沙季节之前；DFe与硝酸盐的比率全年相当恒定（ΔDFe/ΔN=27×10^<-6>[mol/mol]），这一比率与北太平洋中间水（NPIW）相似。基于这些观测结果和简单的模式计算，可以得出结论：小山混合层中Dfe的季节变化主要受春夏生物消耗和冬季NPIW再循环的支配。虽然局部铁沉积有时会产生小范围的高铁斑块，但来自粉尘沉积的铁输入对混合层铁循环的影响较小。[2]在藻华终止期，在oishhio混合层中观测到的DFe数据中，有一半以上显示出0.25 nM的大致恒定值，这意味着藻华形成硅藻在此铁水平以下会产生明显的铁限制。在春季，铁比硝酸盐更快达到这个下限，在春华后期形成限铁生态系统条件。夏季7月，混合层硝态氮的最终耗竭速度快于DFe的最终耗竭速度，在夏季好潮域形成了硝酸盐限制生态系统。

2-D iron distribution in the subarctic northwestern Pacific was investigated repeatedly from 2003 to 2006 with high spacio-temporal resolution equally to major nutrients. Seasonal and interannual variations of iron observed in the Oyashio domain brought us the following information :1] Monthly-mean concentration of dissolved iron (DFe) in the Oyashio mixed layer varies in parallel with nitrate, with its maximum anteceding the Kosa season. Ratio of DFe to the nitrate is fairly constant throughout the year (ΔDFe/ΔN=27×10^<-6>[mol/mol]), and this ratio resembles those of North Pacific intermediate water (NPIW). Based on these observation results and a simple model calculation, it is concluded that the seasonal variation of Dfe in the Oyashio mixed layer is mainly governed by spring-summer biological consumption and winter recirculation from the NPIW. Iron input from the dust deposition is implied to have small effect to the mixed-layer iron cycle, although small-scale high iron patch might sometimes be generated by local iron deposition.2] More than half of the DFe data observed in Oyashio mixed layer at the bloom-termination period shows roughly constant value of 0.25 nM, implying that the bloom-forming diatoms incur significant iron limitation below this iron level. In spring, iron reaches this lower-limit faster than nitrate, forming iron-limited ecosystem conditions at the end of spring bloom. In summer, however, the ultimate depletion of mixed layer nitrate occurs faster than that of DFe at July, forming nitrate-limited ecosystem in the summer Oyashio domain.