Antarctic Deep Water Rates of Export (ANDREX)

地球的气候正在发生变化，就像过去一样。当今科学家面临的巨大挑战之一是了解这些变化的原因和后果。许多科学家寻求这种理解的方式是通过运行基于计算机的气候模拟，模拟海洋、大气、冰和生物之间复杂的相互作用，这些相互作用被认为是驱动气候变化的原因。部分由于这些模拟，我们现在知道海洋环流在调节气候方面起着关键作用。海洋环流中最重要的因素之一是科学家所说的“经向翻转环流”（MOC）。这个术语描述了高纬度地区地表水的冷却和下沉，它们穿过深海，最终在几十年或几个世纪后变暖并返回地面。MOC对气候很重要，因为在这个漫长的海洋循环中，水团携带着热量、碳和其他重要物质，如植物营养物质，这些物质以这种方式分布在地球各地，并长期锁在深海中。MOC最令科学家困惑的阶段之一，也是气候模拟中最不确定的过程之一，是南极大陆附近南极底水（AABW）的形成。AABW是充满MOC最深处的水团，冲刷着全球海洋深渊，将碳和营养物质隔离在深海中。然而，尽管AABW在MOC和气候中占有关键地位，但它仍被许多基本问题所包围。这是因为AABW是在偏远地区形成的，海洋研究船很少访问这些地区。因此，我们目前对AABW形成了多少知之甚少，它是如何从南极海洋出口到世界其他海洋的，以及AABW携带了多少碳和营养物质进入全球海洋深渊。为了开始回答这些问题，我们计划进行一项实验，我们将测量威德尔环流中AABW的生产和出口速度，以及与之相关的碳和营养物质的运输。这是一个椭圆形的洋流，位于南大西洋和西南印度洋的南部边缘，被认为是AABW形成的主要区域。我们将通过(1)测量沿威德尔环流北部边缘的温度、盐度、流速、溶解气体、营养物质和碳的分布来做到这一点；(2)与美国和德国的两组科学家合作，分别沿着环流的东部边缘和环流的西南角进行类似的测量。我们将利用这些前所未有的丰富的观测资料来构建一个进出威德尔环流的水团、碳和营养物质的预算。通过这种方式，我们将能够回答一些关键问题，如“威德尔环流中形成了多少AABW ?”以及“有多少碳和营养物质被AABW锁进了全球海洋的深渊？”我们对这些问题的答案将作为评估最先进的气候和海洋模型技能的基准，并确定未来的气候变化。

The Earth's climate is changing, as it has done in the past. One of the great challenges faced by scientists today is to understand the causes and consequences of these changes. The way many scientists seek this understanding is by running computer-based climate simulations that mimic the complex interactions between the ocean, atmosphere, ice and living beings that are thought to be responsible for driving climate change. It is partly thanks to these simulations that we now know that ocean circulation plays a key role in modulating climate. One of the most important elements of ocean circulation is what scientists know as the 'meridional overturning circulation' (MOC). This term describes the cooling and resulting sinking of surface water masses in high-latitude regions, their journey through the deep ocean and their eventual warming and return to the surface, after many decades or centuries. The MOC is important to climate because the water masses involved in this long circuit through the ocean carry with them heat, carbon and other significant subtances such as plant nutrients, which in this way are distributed around the planet and locked away in the deep ocean for long periods of time. One of the stages of the MOC that puzzles scientists the most, and one of the most uncertain processes in climate simulations, is the formation near the Antarctic continent of Antarctic Bottom Water (AABW). AABW is the water mass that fills the deepest layers of the MOC, flushing the global ocean abyss and sequestering carbon and nutrients in the deep ocean. Yet in spite of its key place in the MOC and climate, AABW is surrounded by many basic questions. This is because AABW is formed in remote regions that are only rarely visited by oceanographic ships. As a result, we currently know little about how much AABW is formed, how it is exported from the Antarctic seas to the rest of the world ocean, and what quantity of carbon and nutrients is carried by AABW into the global ocean abyss. In order to begin answering these questions, we plan to conduct an experiment in which we will measure the rate of AABW production and export, and the associated transports of carbon and nutrients, in the Weddell gyre. This is an oval-shaped current that occupies the southern rim of the South Atlantic and Southwest Indian oceans, and is believed to be the main region in which AABW is formed. We will do this by (1) measuring the distributions of temperature, salinity, current velocity, dissolved gases, nutrients and carbon along the northern rim of the Weddell gyre; and (2) teaming up with two groups of American and German scientists that will make similar measurements along the eastern rim of the gyre and across the gyre's southwestern corner, respectively. We will use this unprecedented richness of observations to construct a budget of the water masses, carbon and nutrients entering and leaving the Weddell gyre. In this way, we will be able to answer key questions such as 'How much AABW is formed in the Weddell gyre?' and 'What quantity of carbon and nutrients is locked away by this AABW into the global ocean abyss?'. Our answers to these questions will serve as a benchmark to evaluate the skill of state-of-the-art climate and ocean models, and to identify future climate change.