Enhanced carbon export driven by internal tides over the mid-Atlantic ridge (CarTRidge)

大西洋中脊内潮汐推动碳输出增强 (CarTRidge)

• 批准号: NE/X014576/1
• 负责人: Alex Poulton
• 金额: $ 38.03万
• 依托单位: Heriot-Watt University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2024
• 资助国家: 英国
• 起止时间: 2024 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FX014576%2F1
• 关键词: Enhanced; carbon; export; driven; internal

Plankton in the ocean, microscopic plants (phytoplankton) and tiny animals (zooplankton) that eat the plants, are vital to marine life and to Earth's climate. They form the base of food chains that support ocean ecosystems, and remove carbon from the atmosphere and bury it in (or export it to) the ocean depths. It is currently thought that plankton are responsible for removing 6 billion tonnes of carbon from the atmosphere each year; fossil fuel burning releases about 10 billion tonnes of carbon into the atmosphere annually. Without this export of carbon in the ocean, atmospheric CO2 would be twice the current concentration. The importance of plankton to food chains and carbon export depends on the species of plankton. Larger phytoplankton are better at supporting food chains and at exporting carbon because (1) larger phytoplankton sink quicker, removing carbon away from the sea surface and contact with the atmosphere, and (2) larger phytoplankton support larger zooplankton, which are eaten by fish and which also excrete large, fast-sinking faecal pellets which quickly transfer carbon away from the atmosphere.We have discovered a new link between which types of plankton can grow and the tides flowing over a mid-ocean ridge. The ocean is layered, with warmer, less dense layers at the surface and colder, denser layers deeper in the ocean. When tidal currents flow up and down the flanks of a mid-ocean ridge, these layers are pushed up and down, causing waves on the layers called "internal tidal waves". These internal tidal waves reach up to the sun-lit upper ocean, where photosynthesis by the phytoplankton takes place. We think these waves have two important effects. (1) The waves cause mixing between the layers of ocean, bringing nutrients from deep in the ocean up to the phytoplankton; this will help extra phytoplankton growth, but crucially it is also known that extra nutrient supplies allow larger species of phytoplankton to grow. (2) The waves move the phytoplankton up and down; this provides more light to the phytoplankton, because as they are moved upward they get closer to the light at the sea surface and are able to grow more. Thus, we think that the internal tidal waves create more growth of larger plankton over a mid-ocean ridge, which means better food for marine food chains and more carbon exported away from the atmosphere.This new link may explain why ridges support such diverse ecosystems, and it also means that the ocean over ridges is far better at exporting carbon than we previously thought. We have calculated that, for the whole Atlantic Ocean, including the tidal effect of the mid-Atlantic ridge adds about 50% to current estimates of how much carbon the plankton export. This means that current understanding of the ocean's role in Earth's climate, which ignores the ridge-tide effect, significantly underestimates how much CO2 plankton remove from the atmosphere. We need to fix this because our predictions of our future climate depend on having correct descriptions of the processes that govern atmospheric CO2.We will conduct an expedition to the mid-ocean ridge in the S. Atlantic. We will measure the internal tidal waves and the upward mixing of nutrients, and the effect the waves have on light received by phytoplankton. We will measure how fast the phytoplankton and zooplankton grow in response to these waves, how the species of plankton change over the ridge, and how much carbon is exported downward over the ridge compared to the adjacent ocean basin. This will be the first time that internal tidal waves are linked to patterns of carbon export in the ocean: internal tidal waves occur wherever there are ridges or seamounts in the ocean and our results will have important global implications for our understanding of ocean food webs and Earth's climate.

海洋中的浮游生物，微观植物（浮游植物）和小动物（浮游动物），它们吃了植物，对海洋生物和地球气候至关重要。它们构成了支持海洋生态系统的食物链的基础，并从大气中清除碳并将其埋入（或导出到海洋深度）。目前，人们认为浮游生物负责每年从大气中清除60亿吨碳；化石燃料燃烧每年将约100亿吨碳释放到大气中。没有海洋中这种碳的出口，大气二氧化碳将是当前浓度的两倍。浮游生物对食物链和碳出口的重要性取决于浮游生物的种类。较大的浮游植物量在支撑食物链和出口碳方面更好，因为（1）较大的植物浮游生物更快，将碳从海面上移开并与大气接触，以及（2）较大的浮游植物支持更大的浮游动物，这些浮游生物是被鱼类食用的，这也可以从中散发出较大的，从而使快速的狂热的狂热的狂热的狂热者，这是快速的狂热的狂热者，既快速又可以转移过来的狂热者。浮游生物可以生长的浮游生物与潮汐中部山脊的潮汐之间的联系。海洋是分层的，表面上有温暖，较少的层，在海洋中较深。当潮流上下流动的中山脊的侧面时，这些层被向上和向下推，从而在称为“内部潮汐波”的层上引起了波浪。这些内部潮汐波到阳光阳光的上大洋，浮游植物的光合作用发生。我们认为这些波浪有两个重要的效果。 （1）波浪在海洋层之间引起混合，从而将营养从海洋深处到浮游植物；这将有助于额外的浮游植物生长，但至关重要的是，众所周知，额外的养分供应允许大型浮游植物物种生长。 （2）海浪上下移动浮游植物；这为浮游植物提供了更多的光，因为随着它们向上移动，它们会靠近海面的光线并能够增长更多。因此，我们认为内部潮汐在中山山脊上会产生更大的浮游生物的增长，这意味着对海洋食品链的食物更好，而碳从大气中出口的碳则更多。这链条可以解释为什么山脊支持如此多样化的生态系统，这也意味着，在出口碳中的山脊上的海洋也比我们以前想到的更好。我们已经计算出，对于整个大西洋，包括中大西洋山脊的潮汐效应，对目前对浮游生物出口的碳的估计增加了约50％。这意味着当前对海洋在地球气候中的作用的理解忽略了山脊潮的效果，这显着低估了二氧化碳浮游生物从大气中移出多少。我们需要解决这个问题，因为我们对未来气候的预测取决于对主导大气CO的过程的正确描述。我们将测量内部潮汐波和营养的向上混合，以及波对浮游植物收到的光的影响。我们将测量浮游植物和浮游动物的响应速度，与相邻的海盆相比，浮游生物的物种如何变化，浮游生物如何变化以及在山脊上向下导出了多少碳。这将是第一次将内部潮汐波与海洋中的碳出口模式联系在一起：海洋中有脊或封口的内部潮汐，我们的结果将对我们对海洋食品网和地球气候的理解具有重要的全球影响。