Collaborative Research: N and Si Dynamics in the Glacial Southern Ocean

合作研究：冰期南大洋中氮和硅的动力学南大洋通过初级生产(碳泵)和富含二氧化碳的深水的通风，在调节过去和现在的大气二氧化碳浓度方面发挥着关键作用。随着时间的推移，评估碳泵的重要性对于理解气候变化是至关重要的。对观测到的较低的冰川二氧化碳浓度提出的一个假设是，铁供应的变化和水柱分层影响了南大洋的生物生产力，从而改变了从南大洋流向低纬海洋的水的营养成分。生物生产的变化很难评估，但两种新的工具--硅藻的硅和氮同位素组成--现在可以估计随着时间的推移对营养物质的消耗。这些技术将应用于现有沉积物岩心的硅藻化石样本，以评估过去两次冰川事件期间南大洋营养物质利用的变化。将这些新结果与现有的替代指标，如生物硅通量和灰尘/铁记录结合起来，将提供对南大洋过去营养动态的估计，并检验通过营养利用改变南大洋和全球生产量的假说。这项研究将有助于更好地理解营养动态和生物地球化学循环如何影响地球气候。更广泛的影响包括与当地K-12教师的互动，帮助年轻学生了解过去和现在的气候变化。该项目还将支持两名以前没有国家科学基金会资助的年轻女科学家的早期职业生涯，并为研究生和本科生提供培训。该项目的成果将广泛传播，数据将张贴在国家地球物理数据中心等网络数据库上。该项目由海洋科学、海洋地质和地球物理计划、极地计划、南极地球科学计划和生物地球化学循环中的新兴课题共同资助。

ABSTRACTCollaborative Research: N and Si Dynamics in the Glacial Southern OceanThe Southern Ocean plays a key role in regulating past and present atmospheric CO2 concentrations through primary production (carbon pump) and ventilation of the CO2-rich deep waters. Evaluating the importance of the carbon pump through time is of primary importance to understanding climate change. One hypothesis proposed to explain the observed lower glacial CO2 concentrations is that changes in the supply of Fe and water column stratification influenced biological productivity in the Southern Ocean which altered the nutrient composition of waters flowing from the Southern Ocean to low latitude oceans. Changes in biological production are difficult to assess but two new tools, the Si and N isotopic compositions of diatoms, now allow estimates of nutrient consumption over time. These techniques will be applied to fossil diatom samples from existing sediment cores to evaluate changes in nutrient use in the Southern Ocean during the past 2 glacial events. Combining theses new results with existing proxies, such as biogenic silica fluxes and dust/Fe records, will provide estimates of past nutrient dynamics in the Southern Ocean and test the hypothesis of changes in Southern Ocean and global production through nutrient use. This research will lead to a better understanding of how nutrient dynamics and biogeochemical cycling affects the climate of the Earth. The broader impacts include interaction with local K-12 teachers to help younger students understand past and present climate changes. The project will also support the early careers of two young women scientists who have not had prior NSF funding as well as provide training of both graduate and undergraduate students. The results of this project will be broadly disseminated and data will be posted on web databases such as the National Geophysical Data Center. This project is jointly funded by the Ocean Sciences Marine Geology & Geophysics Program, Polar Programs Antarctic Earth Sciences Program and Emerging Topics in Biogeochemical Cycle.