The Biological Pump in the Eastern Equatorial Pacific: in situ measurements of Oxygen and Nitrate

在世界海洋阳光照射的表层水域中，浮游植物将营养物质和二氧化碳结合形成有机物并释放氧气。其中一些地表水生物产物最终进入深海，导致海洋表面和大气中碳的净去除。估计向深海输出的碳的一种方法，也被称为“生物泵”，是通过仔细测量与有机物一起产生的氧的数量。溶解在海水中的氧可以通过传感器非常精确地测量，这些传感器可以在系泊、浮子或滑翔机等仪器平台上一次部署数年。在这个项目中，一组调查人员将在赤道太平洋部署12个浮标，测量海洋的温度、盐度、氧气和硝酸盐（浮游植物的营养物质）。这些数据将通过卫星传输，并与海洋环流的计算机模型相结合，以了解这一海洋生产区域的生物泵。该项目将支持两名早期职业研究人员：一名研究生和一名博士后研究员。该项目将在专门装备的剖面浮标上对氧气和硝酸盐进行现场测量，并使用高分辨率全球环流模型（GCM）进行数据解释。该计划是建造12个Argo浮子，专门安装Aanderaa Optode氧气传感器和ISUS硝酸盐传感器，并将它们部署在北纬8度至南纬8度之间的区域，从西经95度到140度不等；在基于卫星和基于gcm的全球碳出口地图中，碳出口最大的位置。这些数据将使用具有生物地球化学元素循环（BEC）样生态系统的区域海洋模式系统（ROMS）物理运输模型，从化学计量学角度解释净生物产氧量，它与年净群落产量（ANCP）和年有机碳出口相关。美国国家科学基金会先前的研究表明，当浮子浮在海面上向岸上传输数据时，通过校准传感器与大气氧气的对比，可以利用浮子上的氧气传感器来确定空气-海洋pO2差异，准确度为正负0.2%。由于海气通量和净生物产量通常是上层海洋氧质量平衡的主要术语，因此可以使用一维上层海洋模式确定亚北极和亚热带环流位置的ANCP。该项目的目标是确定强平流赤道地区的ANCP，并将其与迄今尚未经过观测检验的基于卫星和基于大气遥感的方法确定的碳输出值进行比较。

In the sunlit surface waters of the world's oceans, phytoplankton combine nutrients and carbon dioxide to form organic matter and release oxygen. Some of this surface water biological production ends up in the deep ocean, resulting in a net removal of carbon from the surface ocean and atmosphere. One way to estimate this export of carbon to the deep ocean, also called the "biological pump," is by carefully measuring the amount of oxygen that is produced along with the organic matter. Oxygen dissolved in seawater can be measured very precisely by sensors that can be deployed for years at a time on instrument platforms like moorings, floats, or gliders. In this project, a team of investigators will deploy twelve floats in the equatorial Pacific Ocean to measure ocean profiles of temperature, salinity, oxygen, and nitrate (a nutrient for phytoplankton). The data will be transmitted by satellite and combine with computer models of ocean circulation to understand the biological pump in this productive area of the ocean. The project will support two early-career researchers: a graduate student and a postdoctoral research fellow.The project will be a combination of in situ measurements of oxygen and nitrate on specially-equipped profiling floats with data interpretation using a high-resolution Global Circulation Model (GCM). The plan is to construct 12 Argo floats with specially-mounted Aanderaa Optode oxygen sensors and ISUS nitrate sensors, and to deploy them in the region between 8 degrees N and 8 degrees S from about 95 degrees W to 140 degrees W; the location where carbon export is greatest in both satellite-based and GCM-based maps of global carbon export. The data will be interpreted in terms of net biological oxygen production, which is stoichiometrically related to Annual Net Community Production (ANCP) and annual organic carbon export, using a Regional Ocean Model System (ROMS) physical transport model with a Biogeochemical Elemental Cycling (BEC)-like ecosystem. Previous NSF research has shown that it is possible to determine the air-sea pO2 difference using oxygen sensors on profiling floats to an accuracy of plus or minus 0.2 % by calibrating the sensors against atmospheric oxygen when the floats surface to transmit data to shore. Since the air-sea flux and net biological production are usually the dominant terms in the upper ocean oxygen mass balance, it has been possible to determine ANCP in subarctic and subtropical gyre locations using a one-dimensional, upper-ocean model. The goal in this project is to determine the ANCP in the strongly advective equatorial region, and compare it to carbon export values determined from satellite-based and GCM-based methods that so far have not been tested with observations.