Collaborative Research: Coring in the Southeast Indian and Southern Oceans to examine climate driven changes in watermass paleoventilation, sources, and structure

海洋中的二氧化碳是大气中的50倍。CO2与大气的交换以及CO2在海洋中的储存是大气浓度的重要控制因素。在最近的冰河时期，大气中的二氧化碳浓度自然比工业化前的水平低30%。 大量证据表明，这种减少是由于海洋中二氧化碳储存量增加所致。今天，南大洋由风驱动的海气交换是这两个水库之间CO2交换的主要机制之一。 在末次冰期期间，由于海洋环流的变化和由此产生的海洋化学变化，南大洋的交换减少，据信在海洋中封存更多的二氧化碳方面发挥了重要作用;然而，关于南大洋冰川海洋和大气环流的具体状态仍有争论。目前的研究因缺乏关键地点的适当沉积物岩心而受到阻碍;现有的岩心集中在南大西洋和西南太平洋。这两个区域之间的水团的化学和循环显然发生了变化，但目前几乎没有来自南印度洋关键区域的信息，而今天大部分的二氧化碳交换都发生在那里。在过去30年的研究中，这一地区为数不多的核心已经耗尽。在这项研究中，研究人员将在前往印度洋东南部沃茨的巡航中收集岩心，并进行初步的海岸地层和环境分析。与澳大利亚科学家的合作将是这项工作的一个组成部分，这些核心将成为世界各地科学家的重要资源。该项目支持培养一名研究生和一名博士后研究员。南印度洋中等深度（~500-1400米）水团的循环和通风对大气-海洋CO2分配至关重要。在冰川期，温盐环流和风驱动的南大洋通风的变化被认为在封存大气中的二氧化碳方面发挥了重要作用。详细了解温盐翻转环流和风驱动通风的物理机制之间的相互作用，需要精确定义整个冰消期的水团边界和性质的变化。利用沉积物岩心材料的垂直和水平剖面是查明海洋结构过去变化的基本手段。已发表的断面的古代理在冰川南大西洋有很大的不同，从西南太平洋，导致在东南印度洋的过程有一个重大的影响冰川CO2交换的想法。因此，这项工作将限制表面锋面位置的变化，在大气环流的变化，以及深水质量的边界和海洋环流模式的变化特性。考察的目标是获取30-50个岩心，以便在澳大利亚西部和南部的东南印度洋亚热带和亚热带沃茨建立深度和纬度断面。科学目标是确定代理（如13 C，18 O，Nd同位素）的水平和垂直分布的时间演变，将重建南大洋这一关键区域的水源和通风历史。 科学成果将产生：1）最后一次冰期循环期间南大洋印度洋部分水团代用品的第一个深度断面，2）地表水和深水特性的纬度断面。

Fifty times more CO2 resides in the ocean than the atmosphere. Exchange of CO2 with the atmosphere and the storage of CO2 in the ocean is an important control on atmospheric concentrations. During recent ice ages, atmospheric CO2 concentrations were naturally 30% lower than pre industrial levels. Extensive evidence indicates this reduction was caused by greater storage of CO2 in the ocean. Today, wind-driven air-sea exchange in the Southern Ocean is one of the primary mechanisms for CO2 exchange between these two reservoirs. During the last glacial interval, reduced exchange in the Southern Ocean driven by changes in ocean circulation and the resulting changes in ocean chemistry is believed to have played an important role in sequestering more CO2 in the ocean; however, there is ongoing debate about the specific state of glacial oceanic and atmospheric circulation in the Southern Ocean. Current studies are hampered by a lack of suitable sediment cores from key locations; existing cores are concentrated in the South Atlantic and Southwestern Pacific. There are clearly changes in the chemistry and circulation of water masses between these two regions, but there is little information available from the critical region of the Southern Indian Ocean where much of the CO2 exchange occurs today. The few cores from this area that do exist have been exhausted over the past 30 years of research. In this study, researchers will collect cores on a cruise to Southeast Indian Ocean waters and conduct the initial shore-based stratigraphic and environmental analyses. Collaborations with Australian scientists will be an integral part of this work and these cores will be an important resource for scientists around the world. The project supports the training of both a graduate student and a postdoctoral researcher.The circulation and ventilation of water masses at intermediate depths (~500-1400 m) in the Southern Indian Ocean are central to atmosphere-ocean CO2 partitioning. During glaciations changes in both thermohaline circulation and wind-driven Southern Ocean ventilation are believed to have played an important role in sequestering atmospheric CO2. A detailed understanding of the interaction between the physical mechanisms of thermohaline overturning circulation and wind-driven ventilation requires precise definition of changes in water mass boundaries and properties across the deglaciation. The use of vertical and horizontal transects of sediment core material has been fundamental in identifying past variations in the structure of the ocean. Published transects of paleo-proxies in the glacial South Atlantic differ substantially from the Southwest Pacific, leading to the idea that processes in the Southeast Indian Ocean had a significant influence on glacial CO2 exchange. Consequently, this work will constrain surface frontal locations that shift in response to changes in atmospheric circulation, as well as deep water mass boundaries and properties that vary with ocean circulation patterns. The cruise objective is to obtain 30-50 cores to create depth and latitudinal transects underlying both subantarctic and subtropical waters in the Southeast Indian Ocean from a region west and south of Australia. The scientific objective is to determine the temporal evolution of the horizontal and vertical distribution of proxies (e.g.13C, 18O, Nd isotopes) that will reconstruct the water source and ventilation history of this critical region of the Southern Ocean. The scientific outcomes will be to produce: 1) the first depth transect of water mass proxies in the Indian Ocean sector of the Southern Ocean over the last glacial cycle, and 2) a latitudinal transect of surface and deep water properties.