Impact of the Kuroshio intrusion on the nutrient inventory in the upper northern South China Sea: insights from an isopycnal mixing model
Impact of the Kuroshio intrusion on the nutrient inventory in the upper northern South China Sea: insights from an isopycnal mixing model
复制标题
黑潮入侵对南海北部营养盐库存的影响：来自等密度混合模型的见解
DOI：
10.5194/bg-10-6419-2013
复制
发表时间：
2013-01-01
期刊：
影响因子：
4.9
通讯作者：
Li, Y.
中科院分区：
文献类型：
--
作者：
Du, C.;Liu, Z.;Li, Y.
基于2009-2011年4个航次的调查资料，研究了南海中北方海域极端贫营养沃茨特征的黑潮入侵对营养盐的影响。在研究区域的水柱的上部100米的营养物库存范围从类似于200到类似于290 mmol m（-2）的N+N（硝酸盐加亚硝酸盐），从类似于13到类似于24 mmol m（-2）的可溶性活性磷酸盐和从类似于210到类似于430 mmol m（-2）的柠檬酸。营养盐库存具有明显的季节变化特征，最高值出现在夏季，而N+N库存在春季和冬季分别比夏季减少了约13%和约30%。为了定量黑潮入侵的程度，采用等密度线混合模型，推导出南海本体和黑潮沿着各个等密度线表面的水团的比例贡献。在不考虑地球化学蚀变的假设下，利用沿着等密度面的混合比预测了营养盐的真实梯度。这些预测的营养物浓度，表示为N-m，仅由水团混合决定。结果表明，南海表层100 m的营养盐总量与黑潮水体分数总体呈负相关，表明黑潮入侵对南海营养盐的分布及其季节变化有显著影响。观测到的营养盐浓度和它们相应的Nm之间的差异使我们能够进一步量化与水团混合顶部的地球化学过程相关的营养盐去除/添加。结果表明，在冬季和春季，上层100 m水体中的营养盐均为净消耗，秋季为净增加。
Based on four cruises covering a seasonal cycle in 2009-2011, we examined the impact of the Kuroshio intrusion, featured by extremely oligotrophic waters, on the nutrient inventory in the central northern South China Sea (NSCS). The nutrient inventory in the upper 100m of the water column in the study area ranged from similar to 200 to similar to 290 mmol m(-2) for N+N (nitrate plus nitrite), from similar to 13 to similar to 24 mmol m(-2) for soluble reactive phosphate and from similar to 210 to similar to 430 mmol m(-2) for silicic acid. The nutrient inventory showed a clear seasonal pattern with the highest value appearing in summer, while the N+N inventory in spring and winter had a reduction of similar to 13 and similar to 30 %, respectively, relative to that in summer. To quantify the extent of the Kuroshio intrusion, an isopycnal mixing model was adopted to derive the proportional contribution of water masses from the SCS proper and the Kuroshio along individual isopycnal surfaces. The derived mixing ratio along the isopycnal plane was then employed to predict the genuine gradients of nutrients under the assumption of no biogeochemical alteration. These predicted nutrient concentrations, denoted as N-m, are solely determined by water mass mixing. Results showed that the nutrient inventory in the upper 100m of the NSCS was overall negatively correlated to the Kuroshio water fraction, suggesting that the Kuroshio intrusion significantly influenced the nutrient distribution in the SCS and its seasonal variation. The difference between the observed nutrient concentrations and their corresponding Nm allowed us to further quantify the nutrient removal/addition associated with the biogeochemical processes on top of the water mass mixing. We revealed that the nutrients in the upper 100m of the water column had a net consumption in both winter and spring but a net addition in fall.