Mesoscale Variations of Biogeochemical Properties in the Sargasso Sea
Mesoscale Variations of Biogeochemical Properties in the Sargasso Sea
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DOI：
10.1029/1999jc900021
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发表时间：
1999-06
影响因子：
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通讯作者：
D. McGillicuddy;R. Johnson;D. Siegel;Anthony F. Michaels;N. Bates;A. Knap
中科院分区：
文献类型：
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作者：
D. McGillicuddy;R. Johnson;D. Siegel;Anthony F. Michaels;N. Bates;A. Knap
1996年夏季，在美国联合全球海洋通量研究百慕大大西洋时间序列研究（BATS）地点附近进行了一次中尺度分辨率海洋地球化学调查。流场的实时临近预报和预报有助于对该地区的几个涡流特征进行自适应采样。上层海洋营养盐和色素分布的变化在很大程度上是由与中尺度场相关的垂直等密度线位移控制的。变浅的密度表面倾向于引入冷，营养丰富的水进入真光层，而加深等密度线取代营养贫乏的水向下。叶绿素浓度在前一种情况下普遍增加，而在后一种情况下则降低。真光层底部涡激上升流受到本次调查中捕获的两种不同类型特征的影响：（1）典型的大洋中部气旋，其中主温跃层的隆起使近表层层化向上提升;（2）由18°C厚透镜组成的模态水涡，它推高季节性温跃层并压低主温跃层。模型后报使用所有可用的数据提供了一个四维的背景下，解释时间趋势在BATS网站和其他两个位置在2周的调查后。观测到的近地表结构的变化在BATS网站包括变浅等密度线，增加营养物质的供应在透光层的基础上，并提高叶绿素浓度在透光层。这些趋势可以解释为在这段时间内新形成的气旋袭击了该网站。这些观测结果表明，涡流上升流有一个明显的影响的方式，其中硝酸盐的密度关系的变化与深度从无光区到透光区。一个类似的过渡是存在于BATS记录，表明涡驱动的上升流事件存在于上层海洋地球化学性质的时间序列。在这次天气空间调查中，主要温跃层温度和硝酸盐的变化范围涵盖了迄今为止在最佳技术服务中心可用的10年时间序列（1988-1998年）中观察到的这些量的变化范围。
A mesoscale resolution biogeochemical survey was carried out in the vicinity of the U.S. Joint Global Ocean Flux Study Bermuda Atlantic Time-series Study (BATS) site during the summer of 1996. Real-time nowcasting and forecasting of the flow field facilitated adaptive sampling of several eddy features in the area. Variations in upper ocean nutrient and pigment distributions were largely controlled by vertical isopycnal displacements associated with the mesoscale field. Shoaling density surfaces tended to introduce cold, nutrient-rich water into the euphotic zone, while deepening isopycnals displaced nutrient-depleted water downward. Chlorophyll concentration was generally enhanced in the former case and reduced in the latter. Eddy-induced upwelling at the base of the euphotic zone was affected by features of two different types captured in this survey: (1) a typical mid-ocean cyclone in which doming of the main thermocline raised the near-surface stratification upward and (2) a mode water eddy composed of a thick lens of 18°C water, which pushed up the seasonal thermocline and depressed the main thermocline. Model hindcasts using all available data provide a four-dimensional context in which to interpret temporal trends at the BATS site and two other locations during the 2 weeks subsequent to the survey. Observed changes in near-surface structure at the BATS site included shoaling isopycnals, increased nutrient availability at the base of the euphotic zone, and enhanced chlorophyll concentration within the euphotic zone. These trends are explicable in terms of a newly formed cyclone that impinged upon the site during this time period. These observations reveal that eddy upwelling has a demonstrable impact on the way in which the nitrate-density relationship changes with depth from the aphotic zone into the euphotic zone. A similar transition is present in the BATS record, suggesting that eddy-driven upwelling events are present in the time series of upper ocean biogeochemical properties. The variability in main thermocline temperature and nitrate in this synoptic spatial survey spans the range observed in these quantities in the 10-year time series available at BATS to date (1988–1998).