A Numerical Study of the Patagonia Upwelling Region

巴塔哥尼亚陆架是一个广阔的海底阶地，从拉普拉塔河河口（~36S）延伸到火地岛（~55S）的尖端。卫星和现场观测表明，该地区是一个活跃的上升流中心，拥有世界海洋中一些最大的叶绿素华，其中最独特的是位于大陆架断裂处。巴塔哥尼亚大陆架断裂的上升流将铁和其他营养物质从南大洋的深层带到光带，不仅为大陆架水域提供了养分，也为整个南大西洋的亚极地部分提供了养分。例如，卫星观测显示叶绿素羽流从南美洲延伸到澳大利亚。然而，尽管它对区域和半球产生了影响，但我们对巴塔哥尼亚的上升流机制及其与深海环流的相互作用知之甚少，而这正是本项目打算解决的问题。本研究旨在探讨巴塔哥尼亚冰架断裂上升流的动力机制以及冰架与深海的相互作用。研究的基本前提是陆架断裂上升流主要受底部地形的沿陆架变化和马尔维纳斯海流输送的时间变化调制。这项研究试图量化上升流的时空变化，并将其与大气强迫联系起来。据推测，虽然局地风对上升流的影响可能很小，但大尺度风的变化，特别是太平洋和印度盆地的风的变化可能会显著影响其变率。该研究还将确定巴塔哥尼亚地区最大的跨大陆架交换，并确定控制这些交换的动力机制。预计巴塔哥尼亚在~50S和46S之间通过勒梅尔海峡和大陆架断裂区携带亚南极水域，主要在亚热带大陆架锋处消失。更广泛的影响本研究将有助于西南大西洋地区正在进行和未来的生物和地球化学项目的发展。例如，该项目将开发的上升流指数将有助于将观察到的巴塔哥尼亚生态系统的变化与大陆架断裂上升流的幅度变化和气候变化的大尺度模式联系起来。跨大陆架交换机制（和区域）的确定将有助于我们对碳循环的理解和未来观测计划的发展。作为该项目的一部分，拟议的多学科讲习班将促进国际合作。该项目包括为一名博士生提供支持，该博士生将在整个研究过程中与拉丁美洲的海洋学家密切合作。这一战略应有助于促进对大陆架动力学感兴趣的下一代科学家的南北一体化。在最基本的层面上，该项目提出了关于在气旋西边界流包围的地区产生大陆架断裂上升流和控制跨大陆架交换的动力机制的新想法。这些论点足够普遍，可以适用于其他类似地区（例如，新西兰、日本、威德尔海等），从而扩大了本项目中开发的智力工作的潜在影响。

The Patagonia shelf is a broad submarine terrace that extends from the mouth of the La Plata River (~36S) to the tip of Tierra del Fuego (~55S). Satellite and in-situ observations indicate that this region is an active upwelling center harboring some of the largest chlorophyll blooms of the world ocean, the most distinctive of which is located at the shelfbreak. Patagonia's shelfbreak upwelling brings iron and other nutrient from the deep layers of the Southern Ocean to the photic zone, fertilizing not only the shelf waters, but also the entire subpolar portion of the South Atlantic. Satellite observations, for example, show chlorophyll plumes extending from South America to Australia. Yet, in spite of its regional and hemispheric impact, we know little about Patagonia's upwelling regime or its interaction with the deep-ocean circulation, which this project intends to address. This is a modeling study to investigate the dynamical mechanisms driving Patagonia's shelfbreak upwelling and the interactions between the shelf and the deep ocean. The basic premise is that the shelfbreak upwelling is primarily modulated by the along-shelf variations of the bottom topography and time variations of the Malvinas Current transport. The study seeks to quantify the spatial and temporal variability of the upwelling and link it to the atmospheric forcing. It is hypothesized that, although local wind might have little impact over the upwelling, large-scale wind variations, particularly those over the Pacific and Indian basins might significantly influence its variability. The study will also identify the regions of Patagonia with the largest cross-shelf exchanges and identify the dynamical mechanisms controlling these exchanges. It is anticipated that Patagonia entrains Subantarctic waters through the Le Maire Straits and the shelfbreak region between ~50S and 46S, and primarily detrains at the Subtropical Shelf Front.Broader ImpactsThis study will contribute to the development to ongoing and future biological and geochemical projects of the southwestern Atlantic region. For example, the upwelling index that will be developed by this project will help to relate observed changes in the Patagonia's ecosystems to variations in the magnitude of the shelfbreak upwelling and to large-scale modes of climate variability. The identification of cross-shelf exchanges mechanisms (and regions) will contribute to our understanding of carbon cycles and the development of future observational programs. The multi-disciplinary workshop proposed as part of this project will foster international cooperation. The project includes support for a PhD student who, throughout her/his studies, will work in close collaboration with oceanographers in Latin America. This strategy should help to foster the north-south integration of the next generation of scientists interested in shelf dynamics.Intellectual MeritAt its most basic level this project proposes to test new ideas about the dynamical mechanisms generating shelfbreak upwelling and controlling cross-shelf exchanges in regions bounded by cyclonic western boundary currents. The arguments are general enough to be applicable to other similar regions (e.g., New Zealand, Japan, the Weddell Sea, etc), thus broadening the potential impact of the intellectual work developed in this project.