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: 0961369
• 负责人: Tamay Ozgokmen
• 金额: $ 34.75万
• 依托单位: University of Miami
• 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=0961369&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.

南极底层水（AABW）是全球海洋中主要的深海水体。它是在南极大陆架上形成的非常冷、稠密的水作为密度流出物沿大陆坡下沉而产生的，在下降时夹带周围的深海水团。最近在了解其他主要密度流的动力学和建模方面取得了进展，特别是北欧和边缘海的流。然而，由于缺乏详细的实地数据，在了解南极密度流方面取得的进展较少。因此，目前我们对以下两个基本问题还没有明确的答案：据信确定南极洲周围主要形成点 AABW 的生产率和水文学特征的过程的相对重要性是什么？为什么南极流出物保持足够的密度对比以沉入深海海底，而大多数其他流出物则足够有力地夹带以在中间深度达到中性密度？基于在高能密度流出物及其周围获得的广泛剖面和系泊数据集在2003-2005年西北罗斯海的南极坡（AnSlope）实地计划中，研究人员定义了可以解决上述问题的数值模拟研究。对现场数据的分析和探索性建模工作表明，南极流出量受到以下因素的显着影响：（1）小规模（罗斯比半径以下）地形变化（波纹、等深线收敛、大陆坡曲率、陡坡） ; (2) 流出物与与潮汐等“独立”能量过程相关的横向平流和混合的非线性相互作用； (3)非线性状态方程效应，特别是温压效应。将使用谱元大涡模拟 (LES) 模型进行一系列广泛的数值研究，以研究流出动力学和 AABW 生产对这些因素的敏感性。这些模型将以南极实地数据（AnSlope 和威德尔海南部的补充项目）为指导，但将应用于理想化的地形和水文领域。我们将开发南极密度流出量和 AABW 生产率的参数化，并使用区域海洋建模系统在较粗分辨率的区域海洋模型框架内测试这些参数。该研究将解决改善 AABW 形成在气候系统模型中的代表性的总体目标。智力优点：该项目是 LES 模型首次应用于解决南极洲周围全球底水形成的气候学重大问题。我们将使用该工具来量化影响 AABW 生产率和特性的主要因素在涵盖主要南极流出物的参数范围内的相对重要性。结果将与世界海洋其他地方的流出量进行比较和对比。更广泛的影响：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 产生的能力，这些模型无法解决流出量及其小空间和时间尺度的问题。夹带过程。 AABW 是经向翻转环流的重要组成部分，是全球深海通风的主要贡献者。这笔赠款将支持 RSMAS/UM 的一名研究生。地球与空间研究 (ESR) 联合研究员将继续为西俄勒冈大学拨款提供科学监督，以开发 K-12 课程并教育教师气候科学。演讲将在年度培训研讨会以及俄勒冈州和国家科学教师协会会议上进行。 ESR 和迈阿密大学都维护着专注于教育和推广的特定网页。