Inverse Modeling of the Glacial Ocean

根据该奖项，pi将使用由LeGrand和Wunsch（1995）首先开创的逆建模方法，试图解决末次冰期（距今约21,000年）大西洋深度约2.5公里以下营养丰富的水的起源。通过对底栖有孔虫化石壳上的d13C和Cd/Ca的测量，人们在大约20年前就知道了这一特征。逆模型将用于测试三种可能机制的有效性：深层循环的变化，水质量端元的营养浓度的变化，以及深度有机物再矿化速率的变化。将对LeGrand和Wunsch进行几个关键的扩展：(i)将考虑营养物的非保守性；（ii）底栖生物Cd/Ca和Zn/Ca数据，以及底栖生物a - 13C和a18O数据将被纳入；（iii）将使用西大西洋盆地的最新底栖生物碳13c数据，该盆地是深水的主要流动路径；（iv）模式域将扩展到包括南大西洋，那里的营养物代理数据库自LW95以来已得到很大改进。该项目将包括四项主要任务：(I)对现有的营养替代数据进行关键评估，最后对每个数据的不确定性进行估计；（II）大西洋深处环流逆模式的发展；（三）将模型与现代观测相结合，对模型进行检验，为假设检验提供参考状态；（IV）将模型与数据相结合，以检验大西洋冰川深海中营养物质富集的各种假设。该项目将包括一名研究生和一名博士后研究员，并将有助于填补目前古海洋学家和物理海洋学家之间存在的差距。它将汇集一位建模师、一位古海洋学家和一位物理海洋学家。

Under this award the PIs will use an inverse modeling approach first pioneered by LeGrand and Wunsch (1995), to try to solve the origin of nutrient-rich waters below a depth of about 2.5 km in the Atlantic during the Last Glacial Maximum (around 21,000 years before present). This feature has been known for about two decades from measurements of d13C and Cd/Ca on fossil shells of benthic foraminifera. The inverse model will be used to test the validity of three possible mechanisms: a change in the deep circulation, a change in the nutrient concentration of the water mass end-members, and a change in the rates of organic matter remineralization at depth. Several critical extensions of the LeGrand and Wunsch will be undertaken: (i) the non-conservative character of the nutrients will be considered; (ii) benthic Cd/Ca and Zn/Ca data, in addition to benthic a 13C and a18O, will be incorporated; (iii) new benthic a13C data from the western Atlantic basin, which is a main flow path of deep waters, will be used; and (iv) the model domain will be extended to include the South Atlantic, where the nutrient proxy database has been largely improved since LW95.The project will include four major tasks: (I) a critical assessment of the existing nutrient proxy data, culminating with an estimate of the uncertainty of each datum; (II) the development of an inverse model of the circulation in the deep Atlantic; (III) the combination of the model with modern observations to test the model and to provide a reference state for hypothesis testing; and (IV) the combination of the model with data to test various hypotheses of nutrient enrichment in the glacial abyssal Atlantic. The project will involve a graduate student and a post-doc investigator and will contribute to fill the gap that exists today between the community of paleoceanographers and the community of physical oceanographers. It will bring together a modeler, a paleoceanographer and a physical oceanographer.