Characterizing the Formation, Nature, and Export of Weddell Sea Bottom Water using Noble Gases and Transient Tracers

学术价值：人们普遍认为，至少在上一次冰川盛期以来，全球气候的重大千年时间尺度变化是由海洋子午线翻转环流(MOC)的突然变化引起的，或者至少与之有关。有一种挥之不去的怀疑是，气候瞬变的最终导火索可能在南半球。南极陆架浮力改造形成的密集水域离开陆架并下沉，构成了被称为南极底层水(AABW)的主要水团复合体。AABW是在MOC中起作用的最冷和最稠密的水，它反过来进入所有主要的海洋盆地，从而关闭MOC环路的南端。威德尔海在AABW的产生中占有突出地位，海水和浮动冰架之间的相互作用通过一系列过程产生了AABW的独特前驱光标，这些过程包括：(1)冰缘多尼雅的强热提取、海冰的形成和输出、接地线上冰川的融化以及海底海冰的形成和沉积。这些过程不仅产生了对海洋和气候有重要意义的淡水注入AABW前游标，而且假设对其溶解的惰性气体成分有重大影响。我们建议使用对后者的高精度测量作为这些过程规模的诊断工具。调查员将参加英国的安德烈斯号研究邮轮，这是一个连接CLIVAR(气候可变性和可预测性计划)重复线I6S与南极半岛的路段，将于2009年初进行。邮轮沿着威德尔海环流的北缘，是研究南极绕极洋流中水团交换的理想地点。惰性气体、瞬变示踪剂(氚和放射性碳)以及氯氟烃、稳定同位素、3He和传统水文测量的组合将用于对具有海洋和气候重要性的区域施加限制。广泛影响：该项目涉及开发和使用新的海洋示踪剂，并以新的方式应用更传统的示踪剂，以表征对全球气候系统运行至关重要的水团变化过程。对这些过程的新见解将为下一代海洋-大气耦合气候模式的设计和构建提供有价值的指导，该模式将在应对气候变化造成的广泛经济、政策和社会问题方面具有战略重要性。在这项工作中产生的数据集将提交给适当的数据中心/储存库，供建模师和气候科学家使用，以指导未来的研究工作，并评估或测试现有和未来的气候模型。

Intellectual Merit:It is commonly accepted that since at least the last glacial maximum, the substantial millennial-timescale changes in global climate have been caused by, or at least associated with abrupt changes in the oceanic Meridional Overturning Circulation (MOC). There is the lingering suspicion that perhaps the ultimate trigger of the climate transients may lie in the southern hemisphere. Dense waters formed by buoyancy modification on Antarctic shelf regions leave the shelves and sink to comprise the major water mass complex known as Antarctic Bottom Water (AABW). AABW, the coldest and densest water to play a role in the MOC, in turn enters all of the major ocean basins and thereby closes the southern end of the MOC loop. The Weddell Sea features prominently in the production of AABW, where interaction between seawater and the floating ice-shelves produces a unique pre-cursor to AABW by a combination of processes, including) strong heat extraction at ice-edge polynyas, sea-ice formation and export, melting of glacial ice at the grounding line, and formation and deposition of sub-marine sea-ice. These processes not only produce oceanographically and climatically significant injections of fresh water into the AABW pre-cursor, but are hypothesized to have significant impact on its dissolved noble gas composition. We propose to use high precision measurements of the latter as a diagnostic tool of the magnitude of these processes.The investigator will participate in a British research cruise ANDREX which is a section connecting the CLIVAR (CLImate VARiability and predictability Program) repeat line I6S with the Antarctic Peninsula in early 2009. The cruise follows the northern rim of the Weddell Sea gyre, and is ideally situated to study the exchange of water masses across the Antarctic Circumpolar Current. A combination of noble gases, transient tracers (tritium and radiocarbon) along with CFCs, stable isotopes, 3He, and traditional hydrographic measurements will be used to place constraints on an oceanographically and climatically important region.Broader Impacts:This project involves the development and use of novel oceanographic tracers and the application of more traditional tracers in new ways to characterize water mass transformation processes that are of fundamental importance in the operation of the global climate system. The new insights into these processes will provide valuable guidance in the design and construction of the next generation of coupled ocean-atmosphere climate models, which will be of strategic importance in facing the broad range of economic, policy, and societal issues created by climate change. The data set produced in this work will be submitted to the appropriate data centers/repositories to be made available to modelers and climate scientists to guide future research efforts and to evaluate or test existing and future climate models.