Processes Influencing Carbon Cycling: Observations of the Lower limb of the Antarctic Overturning (PICCOLO)

环绕南极洲大陆的广阔而遥远的海洋被统称为南大洋。这个地区的环境恶劣，多山的海洋，冬季黑暗，强风，冰冻的温度和冰，毫无疑问是全球海洋中探索最少和观测不足的部分之一。然而，由于这些极端现象，它在地球气候系统中发挥着巨大的、尚未量化的作用。在这个地区，大量的热量和二氧化碳在大气和海洋之间交换。控制这些大气-海洋交换的物理机制是NERC ORCHESTRA项目的主题。在PICCOLO中，我们建议将重点放在化学和生物学在这些交流中所起的作用上。特别是，PICCOLO将专注于了解海水中碳的转化机制，当它上升到南极洲附近的表面，与大气、冰、居住在近表面的浮游植物和浮游动物相互作用，然后下降到海洋深处。PICCOLO将对靠近南极洲的地区进行一次海洋研究考察，因为计算机模型和卫星图像显示，这些地区对碳过程至关重要。这些地区结冰的海水会将盐释放到下面的海水中，使其密度增加，从而导致海水下沉。强风导致海冰被吹离南极海岸线，留下一片开阔的水域，称为冰湖。夏季时，水里有足够的光照，浮游植物得以生长，同时也提供了沉入深海的稠密水域，形成了一个巨大的海洋传送带，对地球的气候系统产生了巨大的影响。PICCOLO团队将测量控制该地区生物和化学过程的关键变量，包括铁、营养物质、浮游植物和浮游动物。至关重要的是，该团队将研究该生物和化学系统不同部分之间的控制速率条件。PICCOLO团队将利用最新技术，包括自主潜艇、滑翔机和浮筒，在海冰下等以前无法进入和未研究过的区域观察这些过程。我们最雄心勃勃的计划是将一艘潜艇停泊在一个多冰湖内的海床上，让它在冬季收集数据，并在第二年春天恢复。PICCOLO团队将把仪器安装在密封件上，当他们在水中上下潜水时，这些仪器将不断地收集数据，并通过卫星通信链路将数据实时传回给科学家。PICCOLO团队将利用最先进的计算机模型对这些丰富的新数据进行分析，以检验我们关于整个复杂的物理、化学和生物过程如何影响碳的想法。从概念上讲，我们将沿着一个想象中的水包裹穿过这个系统，观察大气和海洋之间的过程，表层的生物过程，上层和下层海洋之间的交换以及碳的最终归宿。PICCOLO的假设涉及以下方面：(i)控制海洋和大气之间二氧化碳交换的因素以及紫外线在控制海水中二氧化碳浓度方面的作用；（ii）光、铁和营养物在水中浮游生物如何处理碳中的作用；调节碳从上层海洋向深海输出的调节过程；（iv）碳在其全球旅程的下一阶段进入深海的过程。

The vast, remote seas which surround the continent of Antarctica are collectively known as the Southern Ocean. This region with its severe environment of mountainous seas, winter darkness, strong winds, freezing temperatures and ice is unsurprisingly one of the least explored and under-observed parts of the global ocean. However, because of these extremes, it plays a large and still unquantified role in Earth's climate system. In this region, large amounts of heat and carbon dioxide are exchanged between the atmosphere and the ocean. The physical mechanisms controlling these atmosphere-ocean exchanges are the subject of the NERC ORCHESTRA programme. We propose within PICCOLO to concentrate on the role that chemistry and biology play within those exchanges. In particular, PICCOLO will focus on understanding the mechanisms that transform the carbon contained in the seawater as it rises to the surface near Antarctica, interacts with the atmosphere, ice, phytoplankton and zooplankton inhabiting the near surface, before descending to the ocean depths. PICCOLO will undertake an ocean research expedition to the region close to Antarctica, as computer models and satellite images show that these are areas crucial for carbon processes. Freezing seawater in these regions releases salt into the water below, making it denser and therefore causing it to sink. Strong winds cause the sea ice to be pushed away from the Antarctic coastline, leaving areas of open water called polynyas. Within the polynyas the water has enough light during the summer to allow phytoplankton to grow, as well as providing dense waters which sink to the deep, driving a giant ocean conveyor belt which has a large impact upon Earth's climate system. The PICCOLO team will measure the key variables that control the biological and chemical processes in this region including iron, nutrients, phytoplankton and zooplankton. Crucially the team will study the controlling rate terms between different parts of this biological and chemical system. The PICCOLO team will make use of the latest technologies, including autonomous submarines, gliders and floats, to observe these processes in otherwise inaccessible and previously unstudied areas such as under the sea ice. Most ambitiously we will anchor a submarine to the seabed within a polynya and leave it over a winter season to collect data, recovering it the following spring. The PICCOLO team will put instruments on seals which will continuously take data as they dive up and down through the water, sending it back to scientists in real-time via satellite communication links. This wealth of novel data will be analysed by the PICCOLO team, using state of the art computer models, to test our ideas about how the whole complex set of physical, chemical and biological processes affects carbon. Conceptually we will follow an imaginary parcel of water through the system looking at processes between the atmosphere and ocean, biological processes in the surface layer, exchanges between the upper and lower ocean and the final fate of the carbon. The PICCOLO hypotheses address the following: (i) Factors controlling the exchange of carbon dioxide between the ocean and atmosphere and the role of ultra-violet light in controlling the concentration of carbon dioxide in seawater;(ii) The role of light, iron and nutrients in how carbon is processed by the plankton in the water; (iii) The mediating processes governing the export of carbon from the upper ocean to depth;(iv) The processes that take the carbon into the deep ocean on the next stage of its global journey.