Field and Laboratory Program to Evaluate Atlantic Intermediate Circulation During the Past 25,000 Years

在这个项目中，PI将研究深海环流的变化如何影响海洋中的热量、营养物质和碳的分布，以及它们与地球气候和大气中二氧化碳水平的联系。这项研究将检验这样一种假设，即大西洋中南极中水(AAIW)的北流与其作为北大西洋深水(NADW)供应者的角色有关，北大西洋深水的来源是北纬高纬度的表层水下沉，然后在大西洋向南流动。PI预测，当NADW填满大西洋深处的更多区域时，AAIW将进一步向北渗透，以供应NADW。相反，在突如其来的寒冷天气过程中，当NADW的形成被破坏时，AAIW向北的穿透将会减少。为了解决这一假设，PI将使用新的RV Knorr长取心系统从热带大西洋西部(~8 N)收集新的沉积物岩芯。来自化石有孔虫的稳定同位素和镁/钙数据将用于从包括AAIW和NADW在内的所有地下水团的深度生成水团示踪剂的时间序列。更好地了解这些水团的分布历史将有助于更清楚地了解深海环流变化如何影响气候和大气二氧化碳。这项研究的更广泛影响包括四名研究生和一名本科生参与邮轮。一名研究生将使用新材料进行论文研究，而一名本科生将开发一个网站，重点关注邮轮及其科学意义。从该项目获得的数据将在国家气候变化中心的网站上存档，并将纳入历史重建，用于改进对过去海洋环流的模拟，并测试大气环流模型对预测未来气候变化的适用性。沉淀物将提供给其他调查人员。

In this project, the PIs will study how changes in deep ocean circulation influenced the distribution of heat, nutrients, and carbon within the ocean, and their link to earth's climate and levels of CO2 in the atmosphere. The research will test the hypothesis that the northward flow of Antarctic Intermediate Water (AAIW) in the Atlantic Ocean is linked to its role as a supplier of North Atlantic Deep Water (NADW), which derives from sinking of surface waters at high northern latitudes and then flows southward in the Atlantic. The PIs predict that when NADW fills more of the deep Atlantic, AAIW penetrates farther northward to supply NADW. In contrast, during abrupt cold events when the formation of NADW was disrupted, the northward penetration of AAIW would have decreased. To address this hypothesis, the PIs will collect new sediment cores from the western tropical Atlantic (~8 N) using the new RV Knorr long coring system. Stable isotope and Mg/Ca data from fossil foraminifera will be used to generate time series of water mass tracers from depths spanning all subsurface water masses, including AAIW and NADW. Better knowledge of the history of the distribution of these water masses will provide a clearer understanding of how deep ocean circulation changes influence climate and atmospheric CO2. The broader impact of this research includes the participation of four graduate and one undergraduate students on the cruise. One graduate student will use the new material for thesis research while an undergraduate will develop a website focusing on the cruise and its scientific significance. Data obtained from this project will be archived with the NGDC website and will be included in historical reconstructions used to improve simulations of past ocean circulation and to test the suitability of general circulation models to predict future climate change. The sediment will be available to other investigators.