COLLABORATIVE RESEARCH: Tracing Greenhouse to Icehouse Climate Evolution Along the Western North Atlantic Meridional and Paleodepth Transect

合作研究：追踪北大西洋西部经向和古深度横断面从温室到冰库的气候演变

• 批准号: 1657013
• 负责人: Kenneth Miller
• 金额: $ 31.28万
• 依托单位: Rutgers University New Brunswick
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-09-15 至 2021-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1657013&HistoricalAwards=false
• 关键词: COLLABORATIVE; RESEARCH; Tracing; Greenhouse; Icehouse

Earth's climate has changed dramatically in the last 65 million years, from a warm Eocene "greenhouse world" in which the polar regions were temperate and ice-free, to the cold "icehouse world" where glaciers periodically advanced to the mid-latitudes. Solar energy received by the earth has changed little in that time period, so variations internal to the earth system have caused the majority of the observed climate change. Position of continents, changes in ocean currents, and changes in the carbon cycle that affect the atmospheric level of greenhouse gases have all played important roles to in the evolution of Earth's climate. Oceanographic variability in the North Atlantic Ocean has been an important factor for causing periodic large glaciations in the Pleistocene, and the North Atlantic is also hypothesized to be an important climate driver under warmer climate regimes millions of years ago. The research team has designed a site survey to locate targets for collecting sediment sections from the Western North Atlantic under the auspices of the International Ocean Discovery Program (IODP). The seismic reflection survey and sediment records will be used study in detail how the ocean has changed over the last 60 million years, including documenting changes in ocean temperature, deep water flow, and greenhouse gas levels in pre-Pleistocene warm intervals. The records will also be used to better understand how continental configurations and greenhouse gases functioned in tandem to stabilize warm climates. Studying pre-Pleistocene climates will also help scientists understand processes that are likely to affect climate sensitivity in the future. Safe scientific drilling requires high-quality sub-seafloor imaging to identify suitable drill sites. The centerpiece of this project is a 31-day multichannel seismic survey using the Scripps portable high-resolution seismic system. The survey will consist of digital seismic reflection profile acquisition and multibeam mapping at each proposed drill site. These data will not only provide required data for drilling, but also will produce seismic images of changing sediment distribution as sources of deep-water production change through time. Digital seismic reflection profiles will tie the new proposed sites to existing DSDP drill sites to replace poor quality analog seismic data now available. The project will also include a reconnaissance study of Miocene change from legacy DSDP cores in the North Atlantic with well-constrained magnetic reversal stratigraphy to compare evidence for production of Northern Component Water with changes in sea surface temperature gradients, CaCO3 dissolution, and biogenic production. This builds on recent observations that cooling during the middle to late Miocene was delayed in the very high northern latitudes relative to cooling of the deep sea and southern ocean, and will test the hypothesis that cooling was diachronous across latitudes. The IODP drilling will eventually provide continuous Eocene-Holocene sedimentary records that resolve orbital periodicities to compare to similar records from the Pacific. The project supports graduate student training at Rutgers University, and provides sea going experiences for additional graduate students through a "co-chief scientist in training" program.

在过去的6500万年里，地球的气候发生了巨大的变化，从温暖的始新世“温室世界”，其中极地地区是温带和无冰的，到寒冷的“冰库世界”，冰川周期性地前进到中纬度。在这段时间里，地球接收到的太阳能变化很小，因此地球系统内部的变化引起了大部分观测到的气候变化。大陆的位置，洋流的变化，以及影响大气中温室气体水平的碳循环的变化，都在地球气候的演变中发挥了重要作用。北大西洋的海洋变化是导致更新世周期性大冰川的重要因素，北大西洋也被假设为数百万年前温暖气候制度下的重要气候驱动因素。该研究小组设计了一项现场调查，以确定在国际海洋发现计划（IODP）主持下从西北大西洋收集沉积物切片的目标。地震反射调查和沉积物记录将用于详细研究海洋在过去6000万年中的变化，包括记录海洋温度，深水流量和温室气体水平在前更新世温暖时期的变化。这些记录还将用于更好地了解大陆配置和温室气体如何协同作用以稳定温暖的气候。研究前更新世气候也将帮助科学家了解可能影响未来气候敏感性的过程。安全的科学钻探需要高质量的海底下成像，以确定合适的钻探地点。该项目的核心是使用Scripps便携式高分辨率地震系统进行为期31天的多道地震勘探。调查将包括在每个拟议的钻探地点采集数字地震反射剖面图和多波束绘图。这些数据不仅将为钻井提供所需数据，而且还将产生随着深水生产源的时间变化而变化的沉积物分布的地震图像。数字地震反射剖面将把新提议的地点与现有的DSDP钻井地点联系起来，以取代现有的质量差的模拟地震数据。该项目还将包括对北大西洋遗留DSDP岩心中新世变化的勘测研究，并采用约束良好的磁反转地层学，以比较北方成分水生产与海面温度梯度变化、CaCO 3溶解和生物生产的证据。这建立在最近的观察，在中新世中期至晚期的冷却是延迟在非常高的北方纬度相对于深海和南部海洋的冷却，并将测试的假设，冷却是跨纬度历时。IODP钻探最终将提供连续的始新世-全新世沉积记录，这些记录可以解析轨道周期，以与太平洋的类似记录进行比较。该项目支持罗格斯大学的研究生培训，并通过“培训中的联合首席科学家”计划为更多的研究生提供航海经验。