Studies of Turbulence and Mixing in the Antarctic Circumpolar Current, a Continuation of DIMES

南极绕极流湍流和混合的研究，DIMES 的延续

• 批准号: 1232962
• 负责人: James Ledwell
• 金额: $ 322.44万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-09-01 至 2017-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1232962&HistoricalAwards=false
• 关键词: Studies; Turbulence; Mixing; Antarctic; Circumpolar

Intellectual Merit: The Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES) is a study of ocean mixing in the Antarctic Circumpolar Current (ACC) which runs west to east all around the continent of Antarctica, south of the other continents. This current system is somewhat of a barrier to transport of heat, carbon dioxide and other important ocean constituents between the far south and the rest of the ocean, and mixing processes play an important role in those transports. DIMES is a multi-investigator cooperative project, led by physical oceanographers in the U.S. and in the U.K. A passive tracer and an array of sub-surface floats were deployed early in 2009 more than 2000 km west of Drake Passage on a surface of constant density about 1500 m deep between the Sub Antarctic Front and the Polar Front of the ACC. In early 2010 a U.S. led research cruise sampled the tracer, turbulence levels, and the velocity and density profiles that govern the generation of that turbulence, and additional U.K. led research cruises in 2011 and 2012 continue this sampling as the tracer has made its way through Drake Passage, into the Scotia Sea, and over the North Scotia Ridge, a track of more than 3000 km. The initial results show that diapycnal, i.e., vertical, mixing west of Drake Passage where the bottom is relatively smooth is no larger than in most other regions of the open ocean. In contrast, there are strong velocity shears and intense turbulence levels over the rough topography in Drake Passage and diapycnal diffusivity of the tracer more than 10 times larger in Drake Passage and to the east than west of Drake Passage.The DIMES field program continues with the U.S. team collecting new velocity and turbulence data in the Scotia Sea. It is anticipated that the tracer will continue passing through the Scotia Sea until at least early 2014. The U.K. partners have scheduled sampling of the tracer on cruises at the North Scotia Ridge and in the eastern and central Scotia Sea in early 2013 and early 2014. The current project will continue the time series of the tracer at Drake Passage on two more U.S. led cruises, in late 2012 and late 2013. Trajectories through the Scotia Sea estimated from the tracer observations, from neutrally buoyant floats, and from numerical models will be used to accurately estimate mixing rates of the tracer and to locate where the mixing is concentrated. During the 2013 cruise the velocity and turbulence fields along high-resolution transects along the ACC and across the ridges of Drake Passage will be measured to see how far downstream of the ridges the mixing is enhanced, and to test the hypothesis that mixing is enhanced by breaking lee waves generated by flow over the rough topography.Broader Impacts: DIMES (see web site at http://dimes.ucsd.edu) involves many graduate students and post-doctoral researchers. Two graduate students, who would become expert in ocean turbulence and the processes generating it, will continue be trained on this project. The work in DIMES is ultimately motivated by the need to understand the overturning circulation of the global ocean. This circulation governs the transport and storage of heat and carbon dioxide within the huge oceanic reservoir, and thus plays a major role in regulating the earth?s climate. Understanding the circulation and how it changes in reaction to external forces is necessary to the understanding of past climate change and of how climate might change in the future, and is therefore of great importance to human well-being. The data collected and analyzed by the DIMES project will be assembled and made publicly available at the end of the project.The DIMES project is a process experiment sponsored by the U.S. CLIVAR (Climate variability and predictability) program.

智力优势：南冰洋等密度混合实验（英语：Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean，缩写为DIMES）是一项研究南极绕极流（英语：Antarctic Circumpolar current，缩写为ACC）中海洋混合的实验。这一洋流系统在某种程度上阻碍了热量、二氧化碳和其他重要海洋成分在远南和海洋其他部分之间的输送，而混合过程在这些输送中发挥着重要作用。DIMES是一个多研究者合作项目，由美国和英国的物理海洋学家领导。 2009年初，在德雷克海峡以西2000多公里处，在亚南极锋和ACC极锋之间约1500米深的恒定密度表面上部署了一个被动示踪剂和一组次表层浮标。2010年初，美国领导的一次研究巡航对示踪剂、湍流水平、以及控制湍流产生的速度和密度分布，以及其他英国2011年和2012年的研究巡航继续进行这种采样，因为示踪剂已经穿过德雷克海峡，进入斯科舍海，并越过北斯科舍海岭，轨迹超过3000公里。初步结果表明，diapycnal，即，在德雷克海峡以西，海底相对平坦，垂直混合并不比开阔洋的大多数其他区域大。相比之下，德雷克海峡的粗糙地形上存在强烈的速度剪切和强烈的湍流水平，德雷克海峡和德雷克海峡东部的示踪剂的底膜扩散率比德雷克海峡西部大10倍以上。DIMES现场计划继续进行，美国团队收集新的速度和湍流数据在斯科舍海。预计示踪剂将继续通过斯科舍海，至少到2014年初。英国合作伙伴已安排于2013年初和2014年初在北斯科舍海脊以及斯科舍海东部和中部的巡航中对示踪剂进行采样。目前的项目将在2012年底和2013年底的另外两次美国领导的巡航中继续德雷克海峡的示踪剂时间序列。轨迹通过斯科舍海估计从示踪剂的观察，从中性浮力浮子，并从数值模型将被用来准确地估计示踪剂的混合率，并定位混合集中。在2013年巡航期间，将测量沿沿着ACC和跨越德雷克海峡山脊的沿着高分辨率断面的速度和湍流场，以了解在山脊下游多远的地方混合得到加强，并检验以下假设，即混合是通过破碎粗糙地形上的气流产生的背风波得到加强的。http://dimes.ucsd.edu两名研究生将成为海洋湍流及其产生过程方面的专家，他们将继续接受这一项目的培训。DIMES的工作最终是出于了解全球海洋翻转环流的需要。这种环流控制着热量和二氧化碳在巨大的海洋水库中的运输和储存，因此在调节地球方面发挥着重要作用。的气候。了解环流以及它如何对外力作出反应而发生变化，对于了解过去的气候变化和未来气候可能如何变化是必要的，因此对人类福祉至关重要。DIMES项目收集和分析的数据将在项目结束时汇总并公开。DIMES项目是由美国CLIVAR（气候变率和可预测性）计划赞助的一项过程实验。