Collaborative Research: Understanding the Southern Ocean's Contribution to Cenozoic Deep-Water Circulation

海洋环流在地球周围的热量传输以及海洋中碳和营养物质的循环中发挥着重要作用，直接影响着生命和气候。该项目旨在更好地了解两组最大和最重要的深海洋流的历史。起源于南大西洋和北大西洋的海洋水团与阿根廷大陆边缘相交，沿这一边缘积累的海洋沉积物保存了这些水域的循环如何随时间变化的记录。将使用地震成像、海底沉积物采样和海水性质测量的综合计划来调查阿根廷南部边缘及其过去海洋环流的沉积记录。将使用地震技术对1千米以下的海底表面和下面的沉积物进行成像。这一成像将使人们能够更好地了解影响新生代(过去6500万年)边缘的大规模海洋/地质过程。将从一系列水深度收集沉积物岩心和海水性质数据，以重建晚更新世期间水团的成分和几何形状的时间演变。地震调查还将提供必要的信息，为未来的科学钻探计划确定地点。该项目包括学生培训，通过博物馆展品进行公共教育，以及海上活动，可能包括一名海上教师。该实地部分将为研究生提供专业相关的数据获取和解释技术方面的培训机会。南大洋是当今深水到中水循环的引擎，为深海混合提供了大约一半的能量；然而，对更新世晚期温盐环流变化的大多数了解来自北大西洋。由于缺乏关于南大洋水团的深海沉积记录，对这些水团作用的了解受到限制。沿阿根廷边缘大陆斜坡沉积的沉积物提供了一个独特的机会，可以重建起源于南大洋的中深水的全面历史，并更好地了解它们与晚更新世期间全球海洋环流和气候的基本联系。在为期43天的海洋巡航期间，研究小组将从约500米至约5000米的水深处收集地震数据(多波束测绘、高分辨率海底剖面图和多道地震测量)和沉积物岩心(多岩心和活塞岩心)，这个范围跨越了当今南大西洋所有主要中深水域的深度。对一系列物理和地球化学指标的船基和岸基分析将使研究人员能够重建晚更新世期间水团的成分和几何形状的时间演变。结合地震和沉积物数据，将有助于更好地了解构成阿根廷南部边缘的沉积物的性质，以及在晚更新世和新生代影响该边缘的海洋/地质过程。后者将提供广泛的区域和时间背景，以更好地了解沉积物和底流之间的相互作用，以便进一步利用科学的海洋钻探；此外，多通道地震数据将用于确定拟议的钻探地点。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Ocean circulation plays an important role in the transport of heat around the planet and the cycling of carbon and nutrients in the ocean, directly affecting life and climate. This project aims to better understand the histories of two of the largest and most important sets of deep ocean currents. Ocean water masses that originate from both the Southern Ocean and North Atlantic Ocean intersect the continental margin of Argentina and records of how the circulation of these waters changed over time are preserved by the marine sediments that accumulate along this margin. An integrated program of seismic imaging, seafloor sediment sampling, and seawater property measurements will be used to investigate the southern Argentine margin and its sedimentary records of past ocean circulation. Seismic techniques will be used to image the surface of the seafloor and the underlying sediments down to 1 km. This imaging will enable better understanding of the large-scale oceanographic/geological processes that affected the margin over the Cenozoic (the past 65 million years). Sediment cores along with ocean water property data will be collected from a range of water depths to reconstruct the temporal evolution of the compositions and geometries of the water masses during the late Pleistocene. The seismic survey will also provide the requisite information to locate sites for future scientific drilling programs. The project includes student training, public education through museum exhibits, and at-sea activities potentially including a teacher-at-sea. The field component will provide opportunities to train graduate students in professionally relevant data acquisition and interpretation techniques.The Southern Ocean is the engine for today's deep- to intermediate-water circulation, supplying about half of the energy for deep ocean mixing; yet, most understanding of late Pleistocene thermohaline circulation changes derives from the North Atlantic. Understanding of the role of Southern Ocean water masses is limited by a paucity of deep-sea sedimentary records of these water masses. Sediments deposited along the continental slope of the Argentine margin offer a unique opportunity to reconstruct comprehensive histories of Southern Ocean sourced intermediate and deep waters close to their origin, and to better understand their fundamental connections to global ocean circulation and climate during the late Pleistocene. During a 43-day oceanographic cruise to the margin, the research team will collect seismic data (multibeam-mapping, high-resolution subbottom profiling, and multichannel seismic surveying) and sediment cores (multicores and piston cores) from water depths of ~500 to ~5000 meters, a range that spans the depths where all major intermediate and deep waters in the South Atlantic occur today. Ship- and shore-based analyses of a broad suite of physical and geochemical proxies will allow the researchers to reconstruct the temporal evolution of the compositions and geometries of the water masses during the late Pleistocene. The seismic and sediment data combined will enable better understanding of the nature of the sediments that comprise the southern Argentine margin and the oceanographic/geological processes that influenced the margin during both the late Pleistocene and the Cenozoic. The latter will provide a broad regional and temporal context to better understand the interaction between sediments and bottom currents that can be further exploited with scientific ocean drilling; moreover, the multichannel seismic data will be used to situate proposed drilling sites.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.