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内热量、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。这项研究将验证一个假设，即大西洋中向北流动的南极中间水（AAIW）与它作为北大西洋深水（NADW）供应者的角色有关。北大西洋深水来自北纬高纬度地表水的下沉，然后在大西洋中向南流动。PIs预测，当NADW填满更多的大西洋深处时，AAIW将向更北的方向渗透以供应NADW。相反，在突发性冷事件中，当NADW的形成被破坏时，AAIW向北渗透会减少。为了证明这一假设，pi将使用新的RV Knorr长取心系统从西热带大西洋（~8 N）收集新的沉积物岩心。有孔虫化石的稳定同位素和Mg/Ca数据将用于生成包括AAIW和NADW在内的所有地下水质量示踪剂的时间序列。更好地了解这些水团分布的历史将使我们更清楚地了解深海环流变化如何影响气候和大气中的二氧化碳。本研究更广泛的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，重点介绍这次巡航及其科学意义。从该项目获得的数据将存档于NGDC网站，并将纳入历史重建中，用于改进对过去海洋环流的模拟，并测试一般环流模式对预测未来气候变化的适用性。这些沉积物将供其他调查人员使用。

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.