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

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剂以及冰川南大西洋的铁肥化

• 批准号: 0823507
• 负责人: Robert Anderson
• 金额: $ 32万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-09-01 至 2013-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0823507&HistoricalAwards=false
• 关键词: Patagonia; glaciation; geochemical; tracers; Atlantic

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.

提案号NSF OCE 0823507先前的研究已经解释了南大西洋沉积物（纬度40 - 50之间）的证据，表明在末次冰期，存在(1)洋流的快速变化，将热量从热带输送到极地纬度；(2)生物生产力的快速变化与洋流的变化相关。该项目旨在测试以下假设：1)生物生产力的变化是由铁的添加引起的，铁是一种限制生长的必需营养素，由南美洲南部的冰山以土壤的形式运送到该地区；2)提供铁的土壤也携带了一种化学特征（以自生钕（Nd）同位素的形式），这在以前用来推断过去海洋环流变化的证据中引入了一种人工产物。为了验证这些假设，研究人员将确定有机碳（一种衡量生物生产力的指标）和南美洲南部土壤（通过其独特的Nd和Sr同位素组成来确定）的埋藏率在南大西洋中部约45°S的岩心沉积物中是否相关。还将对沉积物中的鱼牙进行研究，以测量其自生Nd同位素组成，因为这些化石提供了比通过浸出块状沉积物获得的更可靠的海水Nd同位素组成测量，而且鱼牙不受土壤携带的钕的影响。重建过去海洋中与气候有关的变化，在发展气候变率的概念和数值模式方面发挥着关键作用，这些模式最终将用于预测未来的气候变化及其后果。因此，这些重建的准确性至关重要。这是本研究项目的关键影响。此外，这项研究将测试过去海洋生物变化及其在全球碳循环中的作用的因果关系，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为因素。