Phytoplankton bloom triggered by an anticyclonic eddy: The combined effect of eddy-Ekman pumping and winter mixing
Phytoplankton bloom triggered by an anticyclonic eddy: The combined effect of eddy-Ekman pumping and winter mixing
复制标题
反气旋涡流引发浮游植物大量繁殖：涡流-埃克曼抽吸和冬季混合的综合作用
DOI：
10.1002/2017jc012763
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发表时间：
2017-06-01
影响因子：
3.6
通讯作者：
Li, Junmin
中科院分区：
文献类型：
--
作者：
He, Qingyou;Zhan, Haigang;Li, Junmin
近年来基于复合材料的研究表明，反气旋涡旋有利于副热带环流中浮游植物的生长。涡旋-埃克曼泵送和冬季混合这两种动力机制已被单独研究过，但它们的相对和综合效应仍不清楚。利用卫星观测和模式模拟，本研究调查了营养枯竭的印度洋东南部反气旋涡旋中产生的独特浮游植物华流的过程。2010年4月下旬至8月，藻华随涡旋向西传播了600多公里。涡旋中地表叶绿素浓度峰值是环境平均值的2.2倍。水华的发展以冬季混合层加深为主，其垂直养分通量速度平均比涡旋-埃克曼泵大3倍。一维物理-生物地球化学模型的结果表明，涡流- ekman泵的作用也是不可或缺的，因为它不仅将额外的营养物质输送到混合层中，而且还导致地下水中叶绿素的显著富集。冬季混合的涡流- ekman泵浦叠加使表层和上层的叶绿素增加了两倍，而地下浮游植物被夹带到混合层中对表层水华有显著贡献，尤其是在水华的初始阶段。卫星观测和模式模拟均表明，涡旋-埃克曼泵送可导致水华提前发生2周以上。
Recent composite based researches reveal that anticyclonic eddies facilitate the growth of phytoplankton in the subtropical gyres. Two dynamical mechanisms, eddy-Ekman pumping and winter mixing, have been examined individually, but their relative and combined effects remain unclear. Using satellite observations and model simulations, this study investigated the process of a distinct phytoplankton bloom generated in an anticyclonic eddy in the nutrient-depleted southeastern Indian Ocean. The bloom propagated westward along with the eddy for more than 600 km from late April to August in 2010. The peak of surface chlorophyll concentration in the eddy is 2.2 times larger than the mean value of the ambient. The development of the bloom is dominated by the winter deepening of mixed layer, whose velocity in vertical nutrient flux is on average 3 times larger than that of eddy-Ekman pumping. The results of a 1-D physical-biogeochemical model demonstrate that the role of eddy-Ekman pumping is also indispensable, because it not only transports extra nutrients into the mixed layer, but also results in significant chlorophyll enrichment in subsurface water. The superposition of eddy-Ekman pumping on winter mixing triples the chlorophyll both at the surface and in the upper layer, and the entrainment of subsurface phytoplankton into the mixed layer contributes significantly to the surface bloom, especially in its initial stage. Both the satellite observations and model simulation show that eddy-Ekman pumping can lead to an early occurrence of the bloom for more than 2 weeks.