Nutrient dynamics in the winter thermohaline frontal zone of the northern shelf region of the South China Sea
Nutrient dynamics in the winter thermohaline frontal zone of the northern shelf region of the South China Sea
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DOI：
10.1029/2009jc005951
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发表时间：
2010-11
影响因子：
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通讯作者：
S. M. Liu;Xinyu Guo;Qi Chen;Jing Zhang;Jing Zhang;Yan-feng Bi;Xinqi Luo;Jian Li
中科院分区：
文献类型：
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作者：
S. M. Liu;Xinyu Guo;Qi Chen;Jing Zhang;Jing Zhang;Yan-feng Bi;Xinqi Luo;Jian Li
[1]作为对南海北方陆架冬季温盐锋区营养盐输运的首次尝试，利用冬季实测资料，研究了锋区营养盐的动力学特征以及锋区水交换对营养盐输运的影响。从沿海到大洋沃茨，水温和盐度都增加，表明存在温盐锋。溶解无机营养盐的浓度向海洋方向下降，特别是在温盐锋，而溶解有机营养盐（即，溶解性有机氮（DON）和溶解性有机磷（DON）呈斑块状分布。氨氮是溶解性无机氮的主要组成部分，DON是溶解性总氮的主要组成部分。PO 43 −/总溶解磷的摩尔比从沿海到海洋沃茨逐渐降低，表明PO 43 −从水柱中迅速去除和/或消耗，有机物降解增加，补充PO 43 −。NO3−/（NH 4 + + DON）的摩尔比为0.01-0.6，表明再生氮占主导地位。在跨岸速度场中确定了表层水辐合和底层水辐散，计算的跨岸营养盐通量表明，冬季温盐锋的存在促进了沿海沃茨营养盐的离岸输送。输送路径以近岸沃茨向锋面辐合开始，然后在锋面下沉，通过锋面近岸底层向海洋移动。在假设南海北方陆架温盐锋长度为500 km的情况下，计算得到的整个温盐锋的营养盐离岸通量大于珠江和长江的营养盐离岸通量。
[1] As the first attempt to estimate the nutrient transport across the winter thermohaline frontal zone on the northern shelf of the South China Sea, the nutrient dynamics around the front and the effects of cross-frontal water exchange on nutrient transport were investigated using wintertime field observations. Both water temperature and salinity increased from coastal to oceanic waters, showing the presence of a thermohaline front. The concentrations of dissolved inorganic nutrients decreased oceanward, especially across the thermohaline front, while those of dissolved organic nutrients (i.e., dissolved organic nitrogen (DON) and dissolved organic phosphorus) showed patchy distributions. Ammonium was the major constituent of dissolved inorganic nitrogen, and DON was the main component of total dissolved nitrogen. Molar ratios of PO43−/total dissolved phosphorus decreased from coastal to oceanic waters, indicating that PO43− was rapidly removed and/or consumed from the water column and that organic matter degradation increased offshore, replenishing PO43−. Molar ratios of NO3−/(NH4+ + DON) were 0.01–0.6, indicating dominance of regenerated nitrogen. Surface water convergence and bottom water divergence were identified in the across-shore velocity field, and the calculated across-shore nutrient fluxes suggest that the presence of the winter thermohaline front promotes the offshore transport of nutrients from coastal waters. The transport path begins with convergence of surface coastal waters toward the front, followed by the sinking in the frontal region and the oceanward movement through the bottom layer of the front offshore side. With an assumption of 500 km as the length of thermohaline front on the northern shelf of the South China Sea, the calculated offshore fluxes of nutrients across the entire front are larger than those from the Zhujiang (Pearl River) and the Changjiang (Yangtze River).