Collaborative Research: GLOBEC-01: Tidal Front Mixing and Exchange on Georges Bank: Controls on the Production of Phytoplankton, Zooplankton, and Larval Fishes

合作研究：GLOBEC-01：乔治滩潮汐锋混合和交换：对浮游植物、浮游动物和幼鱼生产的控制

• 批准号: 0234545
• 负责人: Changsheng Chen
• 金额: --
• 依托单位: University of Massachusetts, Dartmouth
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-09-01 至 2007-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0234545&HistoricalAwards=false
• 关键词: Collaborative; Research; GLOBEC; 01; Tidal

Georges Bank supports a rich fishery because: (1) large portions of the bank are shallow enough that light-limitation of phytoplankton is usually not important; (2) deep waters rich in inorganic nutrients are available for mixing onto the bank; and (3) the Bank's clockwise circulation can retain the planktonic stages of important fish species. The tidally mixed front (TMF) is central to the productivity of Georges Bank through the processes of nutrient injection in the north and retention of larvae on the south flank. These two regions are connected by a circulation pathway along the front in which nutrients lead to phytoplankton and zooplankton growth, creating a donut-shaped region of high production surrounding the crest. It is suggested that the productivity of this pathway is the result of northern edge nutrient injections and is susceptible to climatic influences on nutrient supply in that region. The overall objective of this project is to understand the processes within the TMF that sustain the biological productivity of Georges Bank and the success of the target species, cod and haddock. This requires understanding how mixing and circulation within the TMF supplies new nutrients, supports primary production, and retain larvae. GLOBEC dye tracer experiments have, for the first time, measured directly the near-bottom Lagrangian circulation and mixing in the TMF. Results show that vertical mixing in the front, and the on-bank flow through the base of the TMF, are dynamically connected. This study is examining the 3-dimensional dynamics of the TMF based on these measurements. Models will help assess how the strength of the across- and along-isobath circulation sets time and space scales compatible with the development of cod and haddock larvae. This project consists of a mix of data analysis and modeling activities. First, dye dispersion data and simple shear dispersion models are being used to understand the link between cross-bank flow and vertical mixing. Second, a finite-volume coastal ocean model (FVCOM) will be used to calculate the temporal and spatial structure of nutrient flux into the TMF, contrasting northern and southern flank inputs. A coupled FVCOM- NPZ (nutrient-phytoplankton-zooplankton) model are being used to test the following hypotheses: (i) Nutrient injections in the north are advected around the crest of the bank and lead to a plume of elevated phytoplankton and zooplankton production. (ii) The plume enriches the area of larval entrainment on the south flank. If the above statements are true, then production in the plume can be altered by the nutrient content of source waters in the Northeast Channel of the Gulf of Maine, and these changes will affect the feeding environment of larval cod and haddock. Finally, models incorporating the measured 3-D flow and turbulence fields are being used to examine spatial patterns of larval retention and define the kinds of environmental transitions that larvae experience during this process.

乔治银行（Georges Bank）支持丰富的渔业，因为：（1）银行的大部分地区足够浅，以至于浮游植物的光限制通常并不重要； （2）可以在河岸混合富含无机营养的深水； （3）银行的顺时针循环可以保留重要鱼类的浮游阶段。 潮汐混合的前沿（TMF）是乔治银行在北部的营养注入过程中的生产力和南侧幼虫的保留率的核心。 这两个区域通过沿着养分导致浮游植物和浮游动物生长的循环途径连接，从而形成了围绕波峰的高产量的甜甜圈形区域。 建议该途径的生产力是北部边缘养分注射的结果，并且容易受到气候对该地区养分供应的影响。 该项目的总体目的是了解TMF中维持Georges Bank生物生产力的过程以及目标物种，COD和HADDOCK的成功。 这需要了解TMF内的混合和循环如何提供新的营养，支持初级生产并保留幼虫。 Globec染料示踪剂实验首次直接测量了TMF中的近底拉格朗日循环和混合。 结果表明，正面的垂直混合以及通过TMF底部的银行流动的流动连接。 这项研究基于这些测量值检查了TMF的三维动力学。 模型将有助于评估跨和沿岸循环的强度如何与鳕鱼和黑线径幼虫的发展相吻合的时间和空间尺度。 该项目由数据分析和建模活动组成。 首先，染料分散数据和简单的剪切分散模型被用于了解跨银行流与垂直混合之间的联系。 其次，将使用有限体积的沿海海洋模型（FVCOM）来计算营养通量的时间和空间结构到TMF中，与北侧和南侧的输入对比。 耦合的FVCOM-NPZ（营养 - 潮流 - Zooplankton）模型正在用于检验以下假设：（i）北部的养分注射量在银行的波峰附近促进，并导致升高的浮游植物和浮游植物的生产。 （ii）羽流丰富了南侧的幼虫夹带区域。 如果上述陈述是正确的，那么羽流中的生产可以通过缅因州湾东北海峡的源水的营养含量来改变，这些变化将影响幼虫鳕鱼和黑线径的饲养环境。 最后，使用了结合了测量的3-D流量和湍流场的模型来检查幼虫保留的空间模式，并定义了幼虫在此过程中经历的环境转变的种类。