Collaborative Research: Gases in the Overturning and Horizontal circulation of the Subpolar North Atlantic Program (GOHSNAP)

每年冬天，从北美大陆向东吹来的寒风使位于加拿大和格陵兰岛之间的拉布拉多海的表面沃茨变冷。 随着海洋冷却，大气中的氧气和二氧化碳混合成一层厚厚的水，最终向南扩散，填满北大西洋及更远的地方。 这些水团的存在防止了北大西洋任何地方完全缺乏氧气。 拉布拉多海的垂直混合也将二氧化碳重新分配到深海中，在那里它可以保持数百年，防止它对温室效应的贡献。 然而，海洋吸收气体的过程并没有得到很好的理解或量化。 鉴于在上个世纪，海洋的氧气越来越少，同时也吸收了很大一部分人为二氧化碳，因此观测气体交换过程对于了解和预测海洋和气候系统的演变至关重要。自2014年以来，拉布拉多海的环流一直受到监测，一系列仪器电缆从海底延伸到近海面。 该项目将气体传感器添加到该阵列中，以研究控制气体交换的速率和过程。通过这个项目，学生和博士后将在跨学科海洋学与国际合作者的丰富网络的培训。 为了提高公众的海洋素养，该项目的科学家们将与罗得岛大学的内部空间中心合作，进行现场直播，为合作高中的教育工作者举办互动科学课程，并将在三所参与学校举办面对面的科学咖啡馆。鉴于拉布拉多海在提供氧气（O2）和二氧化碳（CO2）通道方面的独特作用，为了进入海洋的中间深度，对盆地中的气体吸收和运输进行量化和机械理解是一个主要的科学优先事项。拉布拉多海水的氧合防止了大西洋任何地方的大规模缺氧，该盆地的人为二氧化碳储存量是全球海洋中最高的。假设，在大西洋，O2和CO2的吸收和它们的变化是联系在一起的动力学的热损失和翻转环流弥漫的文献，但从来没有被评估的基础上的直接观测。因此，GOHSNAP（副极地北大西洋计划的翻转和水平环流中的气体）解决了这一差距，迫切需要更好地了解气体吸收，运输和翻转环流之间的相互作用。具体而言，该计划将提供连续2年的跨流域记录，在拉布拉多海南部边界的O2的完整水柱运输，利用美国领导的国际次极地北大西洋计划（OSNAP）的系泊基础设施。在该阵列的不同深度增加O2传感器，并辅以自主平台收集的观测数据，将能够量化拉布拉多海的O2输出。 这些数据将进一步用于经验模型碳浓度和估计碳出口。拟议的仪器还将测量混合层O2和pCO 2的两个冬天，从空气-海洋气体交换将被计算和比较，在对流内部的拉布拉多海。这个奖项反映了美国国家科学基金会的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

Every winter, frigid winds blowing eastward from the North American continent cool the surface waters of the Labrador Sea, which is situated between Canada and Greenland. As the ocean cools, oxygen and carbon dioxide are mixed from the atmosphere into a thick layer of water that ultimately spreads southward to fill a large volume of the North Atlantic and beyond. The presence of this water mass prevents the North Atlantic anywhere from becoming completely devoid of oxygen. Vertical mixing in the Labrador Sea also redistributes carbon dioxide into the deep ocean, where it can remain for hundreds of years, preventing it from contributing to the greenhouse effect. Yet, the processes governing the uptake of gases by the ocean are not well understood or quantified. Given that, over the last century, the ocean has become steadily more depleted in oxygen while also absorbing a large fraction of anthropogenic carbon dioxide, observing gas exchange processes is essential for understanding and predicting the evolution of the ocean and climate system. The circulation of the Labrador Sea has been monitored since 2014 with an array of instrumented cables extending from the seafloor to nearly the ocean surface. This project adds gas sensors to this array to investigate the rates and processes governing gas exchange. Through this project, a student and postdoc will be trained in interdisciplinary oceanography with a rich network of international collaborators. Responding to the need to increase public ocean literacy, the project scientists will work with University of Rhode Island’s Inner Space Center to broadcast live, interactive science sessions to educators at partner high schools and will follow-up with in-person science cafés at three participating schools.Given the unique role of the Labrador Sea in providing a pathway for oxygen (O2) and carbon dioxide (CO2) to enter the intermediate depths of the ocean, a quantification and mechanistic understanding of the gas uptake and transport in the basin is a leading scientific priority. Oxygenation of Labrador Sea water prevents large-scale hypoxia from developing anywhere in the Atlantic Ocean and anthropogenic CO2 storage in the basin is the highest in the global ocean. The assumption that, in the Atlantic Ocean, O2 and CO2 uptake and their variability are tied to the dynamics of heat loss and the overturning circulation pervades the literature but has never been evaluated on the basis of direct observations. Thus, GOHSNAP (Gases in the Overturning and Horizontal circulation of the Subpolar North Atlantic Program) addresses this gap and the urgent need to better understand interactions between gas uptake, transport, and the overturning circulation. Specifically, this program will provide a continuous 2-year record of the trans-basin, full water column transport of O2 across the southern boundary of the Labrador Sea, leveraging the mooring infrastructure of the US-lead, international Overturning in the Subpolar North Atlantic Program (OSNAP). The addition of O2 sensors at various depths on this array, supplemented by observations collected by autonomous platforms will allow for the quantification of O2 export from the Labrador Sea. The data will further be used to empirically model carbon concentrations and estimate carbon export. Proposed instruments will also measure the mixed layer O2 and pCO2 for two winters, from which air-sea gas exchange will be calculated and compared against analogous observations in the convective interior of the Labrador Sea.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.