Ocean Circulation, Oxygen and Nutrient Cycles During the Last Glacial Period

俄勒冈州立大学Andreas Schmittner-BoeschOregon State University上一次冰期期间的海洋循环、氧气和营养循环本文试图验证一个基本假设，即在上一次冰期期间从北太平洋观测到的沉积氮同位素数据的千年变化反映了北大西洋深水地层的崩溃，从而导致全球上层海洋营养物质浓度和浮游生物生产力的下降。这种生态转变反过来导致有机质再矿化减少，氧气最低限度区域缩小，全球范围内的反硝化作用下降，并在数百年的规模上做出快速反应。为了解决这个问题，PI将在一个新改进的中等复杂性的大气-海洋耦合模型中嵌入一个氮同位素循环模型，该模型包括生物地球化学，并能够运行数千年。利用该模型进行模拟，并与海洋地质记录进行比较，将为控制过去海洋环流、生产力、氧气和营养循环变化的机制提供新的重要信息。该模型的几个要素将得到改进，包括物理环流(热带动力学)和生物地球化学(这两个都是主要的生物成分，以及与底栖反硝化作用的相互作用)。该模型将预测d15N(和其他示踪剂)变化的区域分布、幅度和时间，以便与地质数据直接比较。更广泛的影响包括对本科生和毕业生的支持，以及一位以前没有得到NSF资助的早期职业科学家。PI将开发他们的地球系统模型，并在项目结束时将其分发给社区使用。

Ocean Circulation, Oxygen and Nutrient Cycles During the Last Glacial PeriodAndreas Schmittner-BoeschOregon State UniversityAbstractThis proposal seeks to test a primary hypothesis that observed millennial variations of sedimentary nitrogen isotope data from the N. Pacific during the last ice age reflect the collapse of North Atlantic Deep Water formation, which then led to a global decrease in upper-ocean nutrient concentrations and plankton productivity. This ecological shift in-turn led to reduced remineralization of organic matter, shrinkage of the oxygen minimum zones, and a decline in denitrification on a global scale, with a rapid response on the scale of hundreds of years. To address this question the PI's will embed a model of nitrogen isotope cycling in a newly improved coupled atmosphere-ocean model of intermediate complexity that includes biogeochemistry, and is capable of multi-millennial runs. Simulations with this model and comparison with the marine geological record will provide new and important information on mechanisms controlling past changes in ocean circulation, productivity, oxygen and nutrient cycling. Several elements of the model will be improved, including the physical circulation (tropical dynamics), and biogeochemistry (both primary biological components, and interactions with the bottom for benthic denitrification). The model will predict the regional distribution, amplitude, and timing of d15N (and other tracers) change for direct comparison with geologic data. Broader impacts include support for undergraduates and graduates and an early-career scientist who has not been funded previously by NSF. The PI's will develop their Earth system model and distribute it for community use at the end of the project.