Collaborative Research: Seasonal Biogeochemical Processes in the Ross Sea: A Modeling Approach

罗斯海是一个海洋学系统，具有几个不寻常的特征，包括在南极最具生物生产力，有较高的鸟类和哺乳动物种群，有相对简单的浮游植物组成，每年都有一致的海冰变化，主要是冰穴，具有季节性低铁浓度，并受到来自罗斯冰架的大型冰山的干扰。许多研究项目已经研究了罗斯海的各种海洋学过程，但仍然缺乏对环流和海洋地球化学过程的综合研究。该项目的总体目标是开发耦合的环流和生物模型，使我们能够了解罗斯海的营养和碳循环，以及评估环流和生物过程对海洋地球化学通量和时空分布的相互作用。这项工作建立在我们现有的高分辨率环流模型（含营养物质）和我们对罗斯海历史营养数据的分析基础上。跨学科研究小组将解决六个研究问题：（1）热，盐，常量营养素和铁的转换途径和交换率是什么？(2)冰山B19和C15对罗斯海西南角的局部环流有什么影响，这些冰山（以及未来可能形成的冰山）的存在是否会影响罗斯冰架下的环流和高盐度陆架水的形成？(3)温暖的海洋水对冰穴形成的贡献是什么？(4)为什么罗斯海冰藻浮游植物的水华开始在10月底，这是明显早于其他水华在同一纬度？，(5)罗斯海内初级生产的命运是否存在区域差异，如果存在，是什么导致了这些差异？以及（6）是什么调节了从光限制系统到铁限制系统的季节转换？为了解决这些问题，将收集对水的性质、水的运动、海洋颜色、营养物浓度和其他地球化学变量的观测，以检验模型的结果。将根据这些数据开发特定产品（例如，T/S体积普查，热量和营养物质的体积通量，总初级生产力和其他），以比较模型的解决方案。研究小组将修改环流模型，以包括罗斯冰架下的空腔，动态海冰，更好的大气强迫，潮汐和铁;此外，现有的生物光学模型也将包括在内，其中包括多种浮游植物类别及其对铁的依赖。将使用垂直和时间（z，t）相关模型来调整物理和生物参数。将开发一个基于伴随的数据同化模型，以根据以前在罗斯海的观测获得一套最佳参数。一维模型将与适当的模型代码、强迫和观测沿着被纳入区域生态系统试验台活动。由于这项研究，调查人员将能够扩大有限的观察，以了解罗斯海的生物地球化学联系，并将具体解决大型冰山对循环和生物过程的影响，以及铁对初级生产和浮游植物分类组成的影响。该项目将通过支持一名研究生和在研究生课程中使用这些结果，为威廉和玛丽学院和旧自治领大学的研究生教育做出贡献。博士后学者将接受海洋模型中生物物理相互作用的扩展培训。 计算机动画将说明罗斯海的基本过程，将在一个网页上提供，并将用于在弗吉尼亚州里士满的弗吉尼亚科学博物馆公开演示。

The Ross Sea is an oceanographic system with several unusual characteristics, including being the mostbiologically productive in the Antarctic, having elevated bird and mammal stocks, having relatively simplephytoplankton composition, having annually consistent sea ice changes dominated by polynyas, havingseasonally low iron concentrations, and being perturbed by large icebergs calved from the Ross Ice Shelf atvarious intervals. A number of research programs have studied various oceanographic processes in the RossSea, but a comprehensive synthesis of circulation and biogeochemical processes remains lacking. Theoverall goal of this project is to develop coupled circulation and biological models that will allow us tounderstand nutrient and carbon cycling in the Ross Sea, as well as to assess the interaction of circulationand biological processes on biogeochemical fluxes and distributions in space and time. This effort builds onour existing fine resolution circulation model (with nutrients) and our analysis of historical nutrient data for the Ross Sea.The interdisciplinary research team will address six research questions: (1) What are the conversion pathways and rates of exchange of heat, salt, macronutrients and iron?, (2) What are the effects of icebergs B19 and C15 on local circulation in the southwest corner of the Ross Sea, and does the presence of these icebergs (and those that might form in the future) affect circulation underneath the Ross Ice Shelf and the formation of High Salinity Shelf Water?, (3) What is the contribution of warm oceanic water to polynya formation?, (4) Why does the Ross Sea polynya phytoplankton bloom begin at the end of October, which issignificantly before other blooms at the same latitude?, (5) Are there regional differences in the fate of primary production within the Ross Sea and if so, what causes these differences?, and (6) What regulates the seasonal transition, from a light- to iron-limited system? To address these questions, observations of water properties, water movement, ocean color,nutrient concentrations and other biogeochemical variables to test the results of the models will be gathered. Specific products will be developed from these data (e.g., T/S volumetric census, volumetric fluxes of heat and nutrients, total primary production and others) to compare to the model solutions. The research team will modify the circulation model to include the cavity beneath the Ross Ice shelf, dynamic sea ice, better atmospheric forcing, tides and iron; furthermore, an existing bio-optical model will be included as well, with multiple phytoplankton classes and their iron dependence. A vertical and time (z,t) dependent model will be used to adjust both physical and biological parameters. An adjoint-based data assimilation model will be developed to obtain an optimal set of parameters based on previous observations in the Ross Sea. The 1-D model will be included in the a regional ecosystem test bed activity along with appropriate model code, forcingand observations. As a result of this study, the investigators will be able to extend the limited observations to understand the biogeochemical linkages in the Ross Sea, and will specifically address the effect of large icebergs on circulation and biological processes and the effect of iron on primary production and phytoplankton taxonomic composition. This project will contribute to graduate education at the College of William and Mary and Old Dominion University through support of a graduate student and the use of these results in graduate classes. A Postdoctoral scholar will receive get expanded training in biological physical interaction in ocean models. Computer animations which will illustrate basic processes in the Ross Sea will be made available on a web page and will be used for public presentations at the Virginia Science Museum in Richmond, VA.