Multi-Decadal Global Surveys of Benthic Nepheloid Layers

准确了解海洋中悬浮颗粒的丰度和分布对于研究海洋生物地球化学循环，特别是与这些颗粒相互作用的痕量元素和同位素至关重要。海底类云状层(BNL)中的粒子可以积累放射性核素，这些放射性核素可用于研究过去的全球变化，作为古代用品，并用于研究现代和冰川海洋环流。该项目旨在评估全球海底云状层地图与表层和深海动能之间的关系，以记录这些过程如何影响深海沉积物再悬浮和再分配过程。这项研究的结果将与海洋界广泛分享。有资格获得国家科学基金会科学、技术、工程和数学项目奖学金的研究生将作为该项目的一部分得到支持和培训。在过去的35年里，研究人员收集了8000多台透射仪-一种光学仪器，经过校准，可以根据大约70次巡航的电导率-温度-密度来估计粒子质量分布。这些已存档和持续收集的透射计数据，以及来自拉蒙特·多尔蒂地球天文台的浊度计数据，是海洋中仅有的涵盖重大时间和全球尺度的颗粒分布的收集。该项目的主要目标是1)将光束衰减数据转换为质量浓度，2)为数千条剖面中的每一条剖面整合净站立存量，3)绘制1980年代至2016年透射计数据的全球地图，4)将这些地图与1960年代至1980年代已绘制初步全球地图的浊度计数据的全球分布进行比较，5)比较发生多次巡航的9条重复水文线上的云状层。将向海洋界广泛传播海底类星状层的全球地图(和辅助数据)，以增进对海底水系的形成、年代际持久性及其与动能制度的关系的科学了解，以便研究、破译和模拟通过水柱和海底附近的生物地球化学循环。

An accurate knowledge of the abundance and distribution of suspended particles in the ocean is essential to the study of marine biogeochemical cycles, especially trace elements and isotopes that interact with these particles. Particles in the benthic nepheloid layer (BNL), a layer of ocean water just above the seafloor, can accumulate radionuclides that are used in studying past global changes, as paleo-proxies, and in investigating modern and glacial ocean circulation. This project aims to assess the relationship between global maps of benthic nepheloid layers and surface and deep sea kinetic energy to document how these processes influence deep-sea processes of sediment resuspension and redistribution. Results from the research will be shared broadly with the oceanographic community. A graduate student who qualifies for the National Science Foundation Scholarships in Science, Technology, Engineering, and Mathematics Program would be supported and trained as part of this project.Over the past 35 years, the investigators have collected more than 8000 transmissometer - an optical instrument calibrated to estimate particle mass - profiles from conductivity-temperature-density casts on approximately 70 cruises. These archived and ongoing collections of transmissometer data along with nephelometer data from the Lamont Doherty Earth Observatory, are the only collections of particle distributions in the ocean encompassing significant temporal and global scales. The main goals of the project are to 1) convert beam attenuation data to mass concentrations, 2) integrate the Net Standing Stock (NetSS) for each of the thousands of profiles, 3) map the NetSS globally from the 1980s-to-2016 transmissometer data, 4) compare these maps against global distributions of nephelometer data from the 1960s-1980s for which a preliminary global map has been constructed, and 5) compare nepheloid layers along 9 Repeat Hydrography lines where multiple cruises have occurred. The global maps (and supporting data) of the benthic nepheloid layers will be widely disseminated to the oceanographic community, enhancing the scientific understanding of BNL formation, decadal persistence, and their relationship to kinetic energy regimes for studying, deciphering and modeling biogeochemical cycles through the water column and near the seafloor.