Collaborative research: Modeling control of Antarctic Bottom Water production by small-scale bathymetry and tides

合作研究：通过小规模测深和潮汐对南极底层水生产进行建模控制

• 批准号: 0961405
• 负责人: Laurence Padman
• 金额: $ 31.6万
• 依托单位: Earth and Space Research
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-07-01 至 2014-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0961405&HistoricalAwards=false
• 关键词: Collaborative; research; Modeling; control; Antarctic

Antarctic Bottom Water (AABW) is the dominant abyssal water mass in the global ocean. It is produced as very cold, dense water formed over the Antarctic continental shelves sinks down the continental slope as a density outflow, entraining ambient deep-ocean water masses as it descends. There has been recent progress in understanding the dynamics and modeling other major density currents, notably those in the Nordic and marginal seas. However, less progress has been made in understanding Antarctic density flows, hampered primarily by a lack of detailed field data. As a consequence we do not, at this time, have a clear answer to two following fundamental questions: What is the relative importance of processes believed to determine the production rate and hydrographic characteristics of AABW at the primary formation sites around Antarctica? Why do Antarctic outflows retain sufficient density contrast to sink to the deep ocean floor, whereas most other outflows entrain sufficiently vigorously to reach neutral density at intermediate depths?Based on an extensive profile and mooring data set obtained in and around an energetic density outflow during the Antarctic Slope (AnSlope) field program in 2003-2005 in the NW Ross Sea, the investigators have defined a numerical modeling study that can address the above questions. Analyses of the field data, and exploratory modeling efforts, suggest that Antarctic outflows are significantly impacted by the following factors: (1) small-scale (sub-Rossby radius) topographic variability (corrugations, isobath convergence, continental slope curvature, steep slopes); (2) nonlinear interaction of the outflow with cross-slope advection and mixing associated with 'independent' energetic processes such as tides; and (3) nonlinear equation-of-state effects, notably thermobaricity. An extensive set of numerical studies using a spectral element Large Eddy Simulation (LES) model will be carried out to study the sensitivity of outflow dynamics and AABW production to these factors. The models will be guided by Antarctic field data (AnSlope, and complementary programs in the southern Weddell Sea), but will be applied to idealized topographies and hydrographic fields. We will develop parameterizations of Antarctic density outflows and AABW production rates, and test these within the framework of coarser-resolution regional ocean models using Regional Ocean Modeling Sysytem. The study will address the overarching objective of improving the representation of AABW formation in climate system models.Intellectual Merits: This project is the first known application of an LES model to the climatologically significant problem of global bottom water formation around Antarctica. We will use this tool to quantify the relative importance of the principal factors influencing the production rate and properties of AABW over parameter ranges that cover the major Antarctic outflows. Outcomes will be compared and contrasted with outflows elsewhere in the world ocean.Broader Impacts: The parameterizations that we will develop will improve our ability to simulate AABW production in earth climate system models that cannot resolve the small spatial and temporal scales of the outflow and its entrainment processes. AABW is a critical component of the meridional overturning circulation and is the dominant contributor to ventilation of the global deep ocean. One graduate student will be supported at RSMAS/UM by this grant. The Earth and Space Research (ESR) Co-investigator will continue to provide scientific oversight for a Western Oregon University grant to develop K-12 curricula and educate teachers in climate science. Presentations will be given at annual training workshops, and Oregon and National Science Teacher Association meetings. Both ESR and the University of Miami maintain specific web pages focused on education and outreach.

南极底水（AABW）是全球海洋中主要的深渊水质量。它的产生是在南极大陆架上形成的非常冷，密集的水作为密度流出，从而下降了大陆坡度，并在下降时散布着环境深ocean水块。在理解动力学和建模其他主要密度电流（尤其是北欧和边际海洋的动力学）方面，最近取得了进展。但是，在理解南极密度流动方面取得了较少的进步，这主要是由于缺乏详细的现场数据而阻碍了。结果，我们目前尚未对以下两个基本问题有明确的答案：被认为确定AABW在南极洲周围主要地层地点的生产率和水文特征的过程的相对重要性是什么？为什么南极流出的流出保持足够的密度与沉入深海的地板形成鲜明对比，而大多数其他外流则足够剧烈地夹带到中间深度处的中性密度？基于广泛的概况和牵制数据集，在在2003-2003-2003-2003-2003-2003 numund ofs the Sea Ardoss in n n n n n nw中，在高清极缝隙中获得的广泛概况和系泊数据集获得可以解决以上问题的建模研究。对现场数据和探索性建模工作的分析表明，南极流出受到以下因素的显着影响：（1）小规模（sub-rossby Radius）地形变异性（波纹，等距，等距收敛，大陆斜率曲率，陡峭的斜坡，陡峭的斜坡）； （2）流出与“独立”能量过程（如潮汐）相关的跨斜率对流的非线性相互作用； （3）非线性方程效应，特别是热生物性。使用光谱元件大型涡流模拟（LES）模型的广泛数值研究将进行研究，以研究流出动力学的敏感性和对这些因素的AABW产生的敏感性。这些模型将由南极田间数据（Anslope和weddell Sea南部的补充程序）进行指导，但将应用于理想化的地形图和水文场。我们将开发南极密度流出和AABW生产率的参数化，并使用区域海洋建模Sysytem在粗分辨率区域海洋模型的框架内进行测试。该研究将探讨改善气候系统模型中AABW形成的表示的总体目标。智能优点：该项目是LES模型在南极洲周围全球底部水形成的气候意义问题上的第一个已知应用。我们将使用此工具来量化影响AABW在覆盖主要南极流出的参数范围的主要因素的相对重要性。结果将与世界海洋其他地方的外流进行比较并形成鲜明对比。BRODER的影响：我们将开发的参数化将提高我们在地球气候系统模型中模拟AABW生产的能力，而ABW气候系统模型无法解析流出的小空间和时间尺度的流出量及其夹带过程。 AABW是子午倾覆循环的关键组成部分，并且是全球深海通风的主要贡献者。这笔赠款将在RSMA/UM的支持下为一名研究生提供支持。地球和太空研究（ESR）共同投资者将继续为西俄勒冈大学提供的科学监督，以开发K-12课程并在气候科学领域教育教师。演讲将在年度培训研讨会，俄勒冈州和国家科学教师协会会议上进行。 ESR和迈阿密大学都保持着专注于教育和外展的特定网页。