Cross-Frontal Fluxes in the Antarctic Circumpolar Current near Udintsev Fracture Zone

乌金采夫断裂带附近南极绕极流的锋面通量

• 批准号: 1358470
• 负责人: D. Randolph Watts
• 金额: $ 89.54万
• 依托单位: University of Rhode Island
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-03-15 至 2019-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1358470&HistoricalAwards=false
• 关键词: Cross; Frontal; Fluxes; Antarctic; Circumpolar

Overview: Across the Antarctic Circumpolar Current (ACC), fluxes of heat and momentum and other dynamical quantities establish the heat budget for the whole Southern Ocean, govern the strength of the ACC and its vital inter-ocean exchanges, and arguably govern the main vertical density structure of the world oceans. Yet, theoretical concepts, numerical models, and the sparse observational records give conflicting views of the mechanisms and magnitude of transfers across the ACC. South of about 55° S the puzzle is further confounded, because the heat fluxes associated with wind-driven Ekman transport and its counterbalancing meridional overturning circulation, that are strong and dominant at lower latitudes, become weak. At that latitude, it falls to cross-frontal processes arising from mean and eddying flow to complete the heat budget. It is particularly puzzling how fluxes cross the several ocean fronts, e.g., from Subantarctic Front to Polar Front to Southern ACC Front. Observations of heat and momentum fluxes and mixing are vitally needed at additional sites around the ACC to inform global climate modeling efforts. Of particular interest is how the oceanic meridional overturning circulation absorbs and redistributes heat and carbon that is critical to the earth's climate. In this study, an array of Current and Pressure recording Inverted Echo Sounders (CPIES) will be deployed for a period of two years to observe and quantify exchanges of buoyancy, heat, momentum and potential vorticity across the ACC as it flows near the Udintsev Fracture Zone in the central South Pacific sector of the Southern Ocean. The CPIES have been shown to be particularly well suited for these measurements. The Udintsev Fracture Zone has been selected because the three main fronts (Subantarctic Front, Polar Front, and Southern ACC Front) converge closely together as they deflect equatorward where they encounter complex shallower ridges and exhibit strong eddy variability in the lee. Therefore, the Udintsev Fracture Zone emerges as a likely location for mean and eddy fluxes to combine to cross the entire ACC system. This project is an international collaboration with a team of French and Korean scientists with complementary goals to deploy tall current meter moorings and conduct CTD surveys in this region.Intellectual Merit: Mesoscale eddies are thought to play a key role in ACC dynamics, with cross-frontal exchange by eddies forming the underpinning of the meridional overturning circulation. Recent studies suggest that this exchange occurs locally in "hot spots" found in the lee of bathymetric obstacles, yet direct estimates of eddy fluxes from ocean measurements are scarce, both globally and especially within the Southern Ocean. Two Current and Pressure recording Inverted Echo Sounders (CPIES) arrays are proposed. The northern array is within the strong eddy region between the Subantarctic Front and Polar Front (where they neighbor closely), and the southern array is located near the Southern ACC Front where historically few measurements have been made. These sites have been selected as candidates where eddy and mean cross-frontal fluxes are likely to be strongest. The CPIES arrays will quantify the role of eddies in redistributing heat, momentum and energy throughout the full water column. The French and Korean tall moorings will provide measurements of currents and temperature at fixed levels, providing complementary estimates of mean and eddy fluxes. The knowledge gained regarding eddy fluxes is crucially important for conceptual understanding of the dynamical balances that control the ACC and drive the overturning circulation and to quantitatively guide future modeling efforts.Broader Impacts: A quality-controlled daily time series of density and currents determined from the CPIES measurements will be disseminated broadly. Combined with data from the current meter moorings, data products suitable for validating numerical models and improving prediction of the cross-frontal flux of momentum, heat, and potential vorticity will be produced. New technology for remote transmission of CPIES data via pop-up data capsules will be tested for use in the strong current, high sea state remote Southern Ocean. Dual pressure sensors will be installed in two CPIES to investigate the calibration-drift of these sensors. An engineering undergraduate student will join the University of Rhode Island technical team and assist CPIES upgrades and preparations.

概述：在南极圆形极电流（ACC），热量和动量的通量以及其他动态数量为整个南部海洋建立了热预算，控制了ACC的强度及其重要的海洋间交流，并且可以说，可以说明世界海洋的主要垂直密度结构。然而，理论概念，数值模型和稀疏的观察记录使整个ACC的机制和幅度矛盾。在大约55°S以南，难题是进一步的混淆，因为与风驱动的埃克曼运输相关的热通量及其平衡的子午倾覆循环，在较低的纬度处呈强大而占主导地位，变得薄弱。在那个纬度上，它落在均值和涡流流的跨额外过程中，以完成热预算。尤其令人困惑的是，磁通量如何跨越多个海洋阵线，例如，从抗北极阵线到极地到南部的ACC前部。在ACC周围的其他站点需要对热量和动量通量和混合进行观察，以告知全球气候建模工作。特别有趣的是，海洋子午线推翻圆如何吸收和重新分布对地球气候至关重要的热量和碳。在这项研究中，将部署一系列电流和压力记录倒置回声声（CPIE）两年，以观察和量化浮力，热，动量和潜在涡度的交换，因为它在南部南部海洋中部太平洋地区的Udintsev骨折区附近流动。 CPIE已被证明特别适合这些测量。之所以选择Udintsev裂缝区域，是因为三个主要前部（亚北极前部，极地前部和南部ACC前部）在击败Equivor Ridges并在Lee中暴露了强烈的涡流变异性时紧密地融合在一起。因此，Udintsev骨折区域是均值和涡流磁通量以跨越整个ACC系统的可能位置。该项目是与法国和韩国科学家团队的国际合作，具有完整的目标，可以在该地区部署高度的电流系泊，并在该地区进行CTD调查。IntlectualFure：Messoccale Eddies被认为在ACC动力学中起着关键作用，并通过形成Meridient the Meridientional complisturning complisturnurnurnurnurnurnurning toclurning the Meridy complunsight的交换中起着关键作用。最近的研究表明，这种交换发生在当地的测深障碍物中发现的“热点”中，但对海洋测量的直接估计是稀缺的，无论是在全球范围内，尤其是在南大洋中。提出了两个电流和压力记录倒置回声声（CPIE）阵列。北部阵列位于亚北极前部和极地前部（它们邻居的地方）之间的强大涡流区域，而南部阵列位于南部ACC沿沿附近，历史上很少进行测量。这些地点已被选为候选者，其中涡流和平均跨额叶通量可能很强。 CPIE阵列将量化涡流在整个水柱中重新分布热，动量和能量中的作用。法国和韩国高的系泊设备将在固定水平下的电流和温度进行测量，从而提供平均和涡流的完整估计。关于涡流的知识对于对控制ACC的动态平衡并推动倾覆的循环并定量指导未来的建模工作至关重要。BRODER的影响：质量控制的日常时间序列密度和从CPIE测量结果确定的质量时间序列。结合当前仪表系泊的数据，适用于验证数值模型的数据产品以及改善动量，热量和潜在涡度的跨额外通量的预测。通过弹出数据胶囊远程传输CPIE数据的新技术将用于强潮，高海洋州偏远的南部大洋。双压传感器将安装在两个CPIE中，以研究这些传感器的校准档位。一名工程本科生将加入罗德岛大学技术团队，并协助CPIES升级和准备工作。