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

罗斯海是一个海洋学系统，具有几个不同寻常的特征，包括在南极最具生物生产力，鸟类和哺乳动物种群数量增加，浮游植物组成相对简单，每年都有一致的海冰变化，主要是冰裂，季节性铁浓度低，并受到罗斯冰架上不同间隔崩解的大型冰山的干扰。许多研究项目已经研究了罗斯海的各种海洋学过程，但仍然缺乏循环和生物地球化学过程的综合。该项目的总体目标是建立耦合的循环和生物模型，使我们能够了解罗斯海的营养和碳循环，并评估循环和生物过程对生物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精细分辨率环流模型（含营养物）和我们对罗斯海历史营养物数据的分析之上。跨学科研究团队将解决六个研究问题：(1)热量、盐、常量营养素和铁的转换途径和交换速率是什么？(2)冰山B19和C15对罗斯海西南角局部环流的影响是什么？这些冰山的存在（以及未来可能形成的冰山）是否影响罗斯冰架下方的环流和高盐度陆架水的形成？(3)暖海水对冰湖形成的贡献是什么？(4)为什么罗斯海多冰区浮游植物在十月底开始大量繁殖，明显早于同纬度的其他植物？(5)罗斯海内初级生产的命运是否存在区域差异？如果存在，造成这些差异的原因是什么？(6)是什么调节了从光限制系统到铁限制系统的季节性转变？为了解决这些问题，将收集对水的性质、水的运动、海洋颜色、营养物质浓度和其他生物地球化学变量的观察，以检验模型的结果。将根据这些数据（例如T/S体积普查、热量和营养物质体积通量、初级生产总量等）开发具体产品，以便与模型解决方案进行比较。研究小组将修改环流模型，包括罗斯冰架下的空洞、动态海冰、更好的大气强迫、潮汐和铁；此外，还将包括一个现有的生物光学模型，其中包括多种浮游植物类别及其对铁的依赖性。一个垂直和时间（z,t）依赖的模型将用于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，以根据罗斯海以往的观测结果获得一组最优参数。1-D模型将与适当的模型代码、强迫和观测一起包括在一个区域生态系统试验台活动中。通过这项研究，研究人员将能够扩展有限的观测，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并在研究生课程中使用这些结果，为威廉玛丽学院和老道明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。说明罗斯海基本过程的电脑动画将在网页上提供，并将用于弗吉尼亚州里士满的弗吉尼亚科学博物馆的公开演示。

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.