Inverse Modeling of the Glacial Ocean

在该奖项下，PI将使用由LeGrand和Wunsch（1995年）首次开创的逆向建模方法，试图解决末次冰期最大期（距今约21，000年）大西洋2.5 km深度以下富含营养物的沃茨的起源。 这一特点已经知道了大约二十年的d13 C和Cd/Ca的底栖有孔虫化石壳的测量。 逆模型将用于测试三种可能机制的有效性：深层环流的变化、水体端元营养物浓度的变化以及深度有机物再矿化率的变化。将对LeGrand和Wunsch进行几项重要的扩展：㈠将考虑营养物的非保守性; ㈡除海底a 13 C和a 18 O数据外，还将纳入海底Cd/Ca和Zn/Ca数据; ㈢将使用来自西大西洋海盆的新的海底a 13 C数据，该海盆是深水沃茨的主要流动通道;该项目将包括四项主要任务：（1）对现有的营养盐代用数据进行严格的评估，最终评估每个数据的不确定性;（II）发展一个深大西洋环流的逆模式;（III）将模式与现代观测相结合，以检验模式，并为假设检验提供一个参考状态;以及（IV）将模型与数据相结合，以检验冰川深海大西洋营养盐富集的各种假设。该项目将涉及一名研究生和一名博士后调查员，并将有助于填补古海洋学家和物理海洋学家之间的差距。它将汇集一名建模师、一名古海洋学家和一名物理海洋学家。

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.