Paleogeochemical and oxygenation history of the Eastern Pacific Ocean

北美和南美的西部大陆斜坡在中等水深处被大量的缺氧水体所沐浴，人们认为这些水体通过限制世界海洋的硝酸盐含量，在全球气候调节中发挥了重要作用。由于硝酸盐是浮游植物的关键营养物质，其在低氧水中的生化损失限制了海洋的生产力。我们一直在研究生物和物理上对这种氧气消耗强度的控制，重点是东北亚热带和亚北极太平洋。我们建议扩展这项工作，重点研究2002年在北美西部边缘发现的22个巨型活塞岩芯中的几个。来自温哥华岛、俄勒冈州和加利福尼亚北部边缘的核心以及加利福尼亚湾是该项目的初始目标。我们的目标是重建过去10万年左右北太平洋广阔地带的海洋生产和中间水循环。研究的重点包括银在大陆边缘沉积物中的分布。我们的新数据表明，沉积银含量随着水深的增加而增加，而我们所做的水柱测量表明，北太平洋上游中间水域的溶液中有银的清除作用。这些现象——目前还没有解释——将在拟议的研究中得到特别关注。最后，我们将探索加拉帕戈斯群岛的生产力历史，以及它与El Niño在过去10,000-20,000年间的联系，通过对沉积物核心的深入研究，该沉积物核心将在2007年前往东赤道太平洋的研究巡航中收集。我们期望这个研究项目将有助于提高对影响和响应地球气候变化的气候历史和海洋学过程的理解。

The western continental slopes of North and South America are bathed at intermediate water depths by large pools of oxygen-poor water that are thought to play a significant role in global climate modulation by limiting the nitrate content of the world's oceans. Because nitrate is a key nutrient for phytoplankton, its biochemically-mediated loss from the low oxygen water constrains the productivity of the sea. We have been investigating controls, both biological and physical, on the intensity of such oxygen depletion through time, focusing on the NE subtropical and subarctic Pacific. We propose to expand this work through a focus on several of 22 giant-piston cores raised from the western margin of North America in 2002. Cores from the Vancouver Island, Oregon, and northern California margins, as well as the Gulf of California are the initial targets in this project.  Our objective is to reconstruct marine production and intermediate water circulation across a broad swath of the North Pacific over the last 100,000 or so years. The research includes a focus on the distribution of silver in continental margin sediments. Our new data show that the sedimentary silver content increases with water depth, while water-column measurements we have made indicate scavenging of silver from solution in upper North Pacific intermediate waters. These phenomena--for which no explanations currently exist--will receive particular attention in the proposed research. Finally, we shall explore the history of productivity in the Galapagos Archipelago and its link to El Niño over the last 10,000-20,000 years through intensive study of a sediment core to be collected during a research cruise to the eastern equatorial Pacific proposed for 2007. We anticipate that this research program will contribute to an improved understanding of both climate history and oceanographic processes that influence and respond to climate changes on Earth.