US GLOBEC: Cross-Frontal Fluxes and Mixing on Georges Bank

乔治·班克上的跨锋通量和混合。Hebert和J.Barth西北大西洋/乔治斯海岸GLOBEC研究的总体目标之一是“确定在强烈潮汐和浮力驱动的系统中控制乔治斯海岸循环和生物、化学和地质材料运输的过程，并确定控制目标物种种群动态的物理和生物过程。在该计划的第三阶段，研究的主要重点将是跨锋交换过程。在这个项目中，研究人员将确定与东北峰锋(3月底/4月初)、陆架/坡锋和乔治斯滩南侧的潮汐混合锋(6月中旬)有关的三维环流。我们将每两周研究一次这些不同锋面的动态。将研究潮流的变化(包括半日和双周时间尺度)对跨锋面交换过程的影响。将尝试确定跨锋面交换的动态和每条锋面的跨锋面交换率。为了实现这些目标，将围绕最初放置在锋面中心的等日拉格朗日浮标进行高分辨率的SeaSoar勘测。SeaSoar将在CTD上安装双重温度和电导传感器，一个潮湿的实验室ac-9光学组件(在9个频率上收集吸收和衰减数据)，一个荧光计和MicroSoar。MicroSoar具有快速的温度和传导性传感器，可以估计温度变化的耗散率(即温度微结构)。舰载声学多普勒海流剖面仪(ADCP)将提供水平速度数据。等边浮标的轨迹将为每一次部署提供一个位置的跨锋面交换路径。CTD和ADCP数据的分析将被用来确定这一交换途径的动力学。盐度、温度和Ac-9数据将被用来描述存在的水团。九种吸收和衰减通道的组合可以作为替代的“示踪剂”来追踪跨额叶交换路径。反复调查可能会让汇率得以确定。微观结构数据将提供湍流混合过程是否重要的信息，如果是，则提供它们发生的位置。这项工作的结果将提供关于水(和水的其他性质)如何通过乔治斯浅滩上发现的不同类型的前锋进行交换的洞察。通过其他GLOBEC PI对同一地点的生物过程和分布的测量，可以解决物理强迫对这些生物过程的影响。

Cross-Frontal Fluxes and Mixing on Georges BankD. Hebert and J. BarthOne of the overall goals of the NW Atlantic/Georges Bank GLOBEC Study is "to determine the processes that control the Georges Bank circulation and transport of biological, chemical, and geological materials in a strongly tidal- and buoyancy-driven system and to determine the physical and biological processes that control the population dynamics of the target species For Phase III of this program, the primary focus of research will be on cross-frontal exchange processes. For this project, the investigators will determine the three-dimensional circulation associated with the Northeast Peak Front (in late March/early April), the Shelf/Slope Front, and the Tidal Mixing Front on the southern flank of Georges Bank (in mid-June). The dynamics of these different fronts over a fortnightly period will be studied. The effect of the variability in the tidal currents (both at the semi-diurnal and fortnightly time-scales) on the cross-frontal exchange processes will be examined. An attempt will be made to determine the dynamics of the cross-frontal exchange and the rate of cross-frontal exchange for each front. To address these goals, high-resolution SeaSoar surveys will be made around an isopycnal Lagrangian float placed initially in the center of the front. The SeaSoar will have dual temperature and conductivity sensors on the CTD, a WET LABS ac-9 optical package (absorption and attenuation data collected at 9 frequencies), a fluorometer and MicroSoar. MicroSoar has fast temperature and conductivity sensors allowing estimates of the temperature variance dissipation rate (i.e., temperature microstructure) to be made. A shipboard Acoustic Doppler Current Profiler (ADCP) will provide horizontal velocity data. The trajectory of the isopycnal float will provide the cross-frontal exchange pathway for one location for each deployment. Analysis of the CTD and ADCP data will be used to determine the dynamics of this exchange pathway. The salinity, temperature and ac-9 data will be used to characterize the water masses present. Combinations of the nine absorption and attenuation channels can be used as surrogate "tracers" to track cross-frontal exchange pathways. Repeated surveys may allow the exchange rates to be determined. The microstructure data will provide information if turbulent mixing processes are important and, if so, where they occur. The results of this work will provide insight on how water (and other properties of the water) are exchanged across the different types of fronts found on Georges Bank. With the measurements of biological processes and distributions at the same location made by other GLOBEC PIs, the effect of physical forcing on these biological processes can be addressed.