Carbon Uptake and Seasonal Traits in Antarctic Remineralisation Depth (CUSTARD)

海洋表面是数十亿被称为浮游植物的微生物的家园，它们利用阳光和二氧化碳在海洋表面产生有机物质。当它们死亡时，其中许多会下沉，将这些碳带入深海，在那里可能会储存数百至数千年，这有助于保持我们今天的气候。一般来说，它们对我们气候影响的大小与它们在溶解前下沉的深度有关--它们下沉得越深，储存的碳就越多。这种影响在南大洋的北方部分尤其重要，那里的洋流模式意味着，浅层和深层溶解之间的差异控制着这些碳是在几年还是几个世纪内被锁定在海洋表面。这是因为该地区是海洋环流的交汇点。从地表到海底，在近5公里的深度，四条海洋“高速公路”相互堆叠，将水带到全球海洋的不同部分。碳被溶解的高速公路决定了它将远离大气多久。出于这个原因，如果我们想了解南大洋北方在调节全球气候方面的作用，我们需要了解海洋表面的碳吸收量以及下沉物质的溶解程度。不幸的是，我们对两者都不太了解;南大洋的数据很少，因为天气不好，很少有商业船只经过那里。因此，我们关于碳沉降的命运模式以及控制它的因素的理论还没有得到验证。因此，我们用来预测未来气候的模型在这一地区具有很大的不确定性。然而，我们所拥有的证据表明，碳溶解深度的变化是理解该系统如何工作的关键。 在这个项目中，我们将通过使用机器人车辆和先进的新传感器的令人兴奋的组合在南大洋的偏远地区进行新的观测来解决这个问题。我们将对海洋在南大洋这个关键的高速公路交汇处吸收了多少碳进行新的观察。我们将研究控制碳的吸收及其命运的过程，特别是营养物质的季节性供应如何影响浮游植物的组成，从而改变碳在溶解之前下沉的深度。我们将联合收割机将这些观测结果与一种新的建模方法相结合，使我们能够比正常情况下更快地运行气候模型中的海洋部分。这使我们能够探索在我们的数据中发现的营养物质和浮游植物之间的季节性相互作用的后果。特别是，该模型允许我们“标记”碳，以便我们可以跟踪它的去向。通过这种方式，我们可以测量每一条高速公路上的碳沉降量，以及这一年中的变化情况。 再加上对营养物和碳沉降的季节性变化的观察，该模型将使我们能够确定调节这一重要领域碳吸收的关键过程。这将为那些建立联合王国气候模型的人提供重要信息，同时该模型正在开发中，为未来关于世界气候状况的高调报告（来自IPCC）提供投入。

The surface ocean is home to billions of microscopic plants called phytoplankton which produce organic matter in the surface ocean using sunlight and carbon dioxide. When they die many of them sink, taking this carbon into the deep ocean, where it may be stored for hundreds to thousands of years, which helps keep our climate the way it is today. In general terms the size of the effect they have on our climate is linked to how deep they sink before they dissolve - the deeper they sink, the more carbon is stored. This effect is particularly important in the northern part of the Southern Ocean where the pattern of ocean currents means that the difference between shallow and deep dissolution controls whether this carbon is locked away from the surface ocean for just a few years or for centuries. This is because the area is a junction in the ocean circulation. Stacked up on each other from the surface to the seafloor at almost 5km depth are four oceanic 'motorways', taking water to different parts of the global ocean. The motorway that the carbon is dissolved into determines how long it will be kept away from the atmosphere. For this reason, if we want to understand the role of this northern part of the Southern Ocean in regulating global climate we need to understand both how big carbon uptake is at the ocean surface and also how deep sinking material dissolves. Unfortunately we don't understand either well; data are scarce in the Southern Ocean as the weather is poor and few commercial vessels pass through there. Consequently, our theories about the pattern of the fate of sinking carbon and what controls this are untested. As a result the models that we use for predicting future climate have massive uncertainty in this region. However, the evidence that we have suggests that changes in the depth of carbon dissolution are key to understanding how the system works. In this project we will tackle this by making new observations in a remote region of the Southern Ocean using an exciting combination of robotic vehicles and sophisticated new sensors. We will make new observations of how much carbon the ocean takes up in this key motorway junction of the Southern Ocean. We will examine the processes that control the uptake of carbon and its fate, in particular how seasonal availability of nutrients can affect the make-up of the phytoplankton which changes the depth to which carbon sinks before being dissolved. We will combine these observations with a novel modelling approach that allows us to run the ocean part of our climate model much faster than normally. This allows us to explore the consequences of the seasonal interplay between nutrients and phytoplankton found in our data. In particular, the model allows us to 'tag' carbon so that we can trace where it goes. In this way we can measure the amount of sinking carbon ending up on each motorway and how this varies through the year. Together with observations of the seasonal changes in nutrients and sinking carbon the model will allow us to determine the key processes regulating carbon uptake in this important area. This will provide important information to those building the UK's climate model at a time when it is being developed to provide input to a future high profile report (from the IPCC) on the state of the world's climate.