Patagonia glaciation, geochemical tracers of Atlantic Meridional Overturning Circulation, and iron fertilization of the glacial South Atlantic Ocean

项目名称：巴塔哥尼亚冰川作用、大西洋经向翻转环流的地球化学示踪和南大西洋冰川的铁的肥沃。以前的研究解释了南大西洋沉积物(在40到50度纬度之间)的证据表明，在最后一次冰川时期，(1)将热量从热带输送到极地纬度的洋流发生了快速变化，(2)生物生产力的迅速变化与洋流的变化有关。该项目旨在检验以下假设：1)生物生产力的变化是由于添加了铁造成的，铁是一种限制生长的基本营养物质，以南美洲南部冰山携带的土壤的形式输送到该区域，2)提供铁的土壤也带有化学特征(以自生钕(ND)同位素的形式)，这在以前用于推断过去海洋环流变化的证据中引入了一种人工制品。为了验证这些假设，研究人员将确定有机碳(一种生物生产力的衡量标准)和南美洲南部土壤(由其独特的ND和Sr同位素组成确定)的埋藏率是否与南大西洋中部约45°S岩心的沉积物相关联。研究人员还将对沉积物中的鱼牙进行研究，以测量其自生的ND同位素组成，因为这些化石提供了比淋滤大量沉积物更可靠的海水ND同位素组成的衡量标准，而且鱼牙不受土壤携带的钕的影响。对过去与气候有关的海洋变化的重建在发展气候变异性的概念模型和数值模型方面发挥着关键作用，这些模型最终将有助于预测未来的气候变化及其后果。因此，这些重建必须准确。这是这一研究项目的关键和更广泛的影响。此外，这项研究将测试过去海洋生物变化背后的因果关系及其在全球碳循环中的作用，并测试可能混淆先前对海洋环流中气候相关变化的解释的潜在人工产物。

Proposal Number NSF OCE 0823507 Project Title: Patagonia glaciation, geochemical tracers of Atlantic Meridional Overturning Circulation, and iron fertilization of the glacial South Atlantic Ocean AbstractPrevious studies have interpreted evidence from South Atlantic sediments (between 40 and 50S latitude) to indicate that, during the last glacial period, there were (1) rapid changes in ocean currents that transport heat from the tropics to polar latitudes, and (2) rapid changes in biological productivity correlated with the changes in ocean currents. This project is designed to test the following hypotheses: 1) Changes in biological productivity were caused by the addition of iron, a growth-limiting essential nutrient, delivered to the region in the form of soil carried by icebergs from southern South America, and 2) The soil that provided the iron also carried a chemical signature (in the form of authigenic neodymium (Nd) isotopes) that introduced an artifact in the evidence used previously to infer past changes in ocean circulation. To test these hypotheses, researchers will determine if the burial rates of organic carbon (a measure of biological productivity) and of soil from southern South America (identified by its unique composition of Nd and Sr isotopes) are correlated in sediments from cores in the mid South Atlantic at about 45°S. Research will also be conducted on fish teeth from the sediments to measure their authigenic Nd isotope composition because these fossils provide a more reliable measure of the Nd isotope composition of seawater than is obtained by leaching bulk sediments and fish teeth are not influenced by neodymium carried by soil. Reconstructions of past climate-related changes in the ocean play a critical role in developing both conceptual and numerical models of climate variability that will ultimately serve to make predictions of future climate change, and of its consequences. Consequently, it is vital that these reconstructions be accurate. This is key broader impact of this research project. In addition, this study will both test cause and effect relationships underlying past changes in ocean biology and its role in the global carbon cycle, and test for potential artifacts that may have confused previous interpretations of climate-related changes in ocean circulation.