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.

智力优点：南大洋（DIMES）的二比和异，等级混合实验是对南极循环电流（ACC）的海洋混合的研究，该海洋混合在其他大陆以南的南极洲大陆周围向西延伸。当前的系统在某种程度上是对远南和其他海洋之间的热量，二氧化碳和其他重要的海洋成分的运输的障碍，并且混合过程在这些运输中起着重要作用。 Dimes是一个多侵入式合作项目，由美国和英国的物理海洋学者领导。一个被动示踪剂和一系列的地下浮子在2009年初部署了Drake Passage以西2000公里以西的恒定密度以西2000公里以上的恒定密度的表面，该表面是ACP的恒定密度，大约1500 m。 2010年初，美国一项领导的研究巡游取样了示踪剂，动荡水平以及控制这种动荡产生的速度和密度概况，而额外的英国领导的研究在2011年和2012年继续进行了研究，因为示踪剂已经通过Drake Passage，进入了Scotia Sea，并在Scotia Sea上，以及北Scotia Ridge，一支比3000 km的轨道骑行，继续进行了这种采样。最初的结果表明，Diapynal，即垂直的，在Drake Passage的西部混合，其中底部相对光滑的情况并不大于在开阔的大多数其他区域。相比之下，在Drake通道中的粗糙地形上，示踪剂的粗糙地形和强烈的湍流水平强的速度剪切和强烈的湍流水平超过10倍以上的Drake通道，而在Drake Passage的西部则是Dimes Field Program的延续。可以预计，示踪剂将继续穿过斯科舍省海洋，至少至少在2014年初。从示踪剂观测值，中性浮力的浮子和数值模型中估计，将用于准确估计示踪剂的混合速率，并定位混合浓缩的位置。在2013年巡航期间，将测量沿ACC和Drake通道的高分辨率沿高分辨率的速度和湍流场进行测量，以查看混合的山脊下游的远距离，并测试混合的假说，即通过流行而越过流程来增强混合的假设。 http://dimes.ucd.edu）涉及许多研究生和博士后研究人员。两名将成为海洋湍流专家并产生的过程的研究生将继续接受该项目的培训。一角钱的工作最终是出于了解全球海洋倾覆的循环的必要性。该循环控制着巨大的海洋水库中热和二氧化碳的运输和存储，因此在调节地球气候中起着重要作用。要了解对过去气候变化以及将来气候如何变化的循环及其对外部力量的反应的变化，因此对人类的福祉至关重要。由Dimes项目收集和分析的数据将在项目结束时进行组装并公开提供。Dimes项目是由美国Clivar（气候可变性和可预测性）计划赞助的过程实验。