Collaborative Research: Deep Drilling of Lake Junin, Peru: Continuous Tropical Records of Glaciation, Climate Change and Magnetic Field Variations Spanning the Late Quaternary

合作研究：秘鲁胡宁湖深钻：晚第四纪冰川作用、气候变化和磁场变化的连续热带记录

• 批准号: 1400903
• 负责人: Joseph Stoner
• 金额: $ 34.3万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-06-01 至 2019-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1400903&HistoricalAwards=false
• 关键词: Collaborative; Research; Deep; Drilling; Lake

Our ability to understand the full complexity of climate change and forecast future regional trends requires that we extend the available instrumental records into the geologic past. Over the past several decades paleoclimatologists have developed myriad proxy indicators of past regional climate that are recorded in natural archives such as ice cores, cave deposits, and lake sediment, among many other archives. Proxy paleoclimate records from the tropics are particularly important because this region is the ?heat engine? of Earth. Long- and short-term changes in ocean-atmosphere circulation that are manifested in such phenomenon as the El Nino Southern Oscillation (ENSO), the mean position of the Intertropical Convergence Zone, and the response of the tropics to high latitude climatic ?events? are critical to understand because these phenomena can have a profound impact on regional water balance, which directly affects potable water supplies, hydroelectricity generation, and agricultural productivity. The longest continuous records of climate change in the tropics are limited to those derived from the relatively few old lake basins in the region. Lake Junin, the largest lake located entirely within Peru, is among the oldest lake basins in South America. It contains a sediment record that is at least 200 m long that may extend more than 250,000 years. Lake Junin is exceptional in the length of record that it contains, but also in the climate signals that it records. Considerable prior research has documented that Lake Junin records the waxing and waning of nearby alpine glaciers and changes in regional water balance through the isotope geochemistry of calcium carbonate deposited on the lake bottom at a rate of approximately 0.2 to 1.0 mm/yr. This research will develop these and other proxy climate records for the full length of recovered core; the records generated will comprise one of the longest continuous records of climate and environmental change from the inner tropics. The Lake Junin Drilling Project has several broader impacts. These include the joint renovation of an abandoned lodge for future shared use as the first shoreline outpost for officials of the Junin National Reserve, as a visitor center, and as a lake access point for ecotourism. Capacity building activities in the Junin Project include collaboration with Peruvian universities, training of geoscientists, as well as Peruvian and American student training. A specific team will be responsible for the organization of lectures at villages in the region to inform citizens about the significance of the drilling, and will work closely with the national park service to instruct the rangers on how to use the science to promote conservation efforts around the lake. During the drilling, a team will facilitate interactions with local and international media. The team expect to involve U.S. and Peruvian students in all aspects of Junin drilling, and much of the paleoecological research related to the Junin cores will be conducted by graduate students. Training opportunities during the drilling phase of operations are also planned for geoscientists from Peruvian universities. Numerous U.S. undergraduate and graduate students, and one postdoctoral fellow will be involved in all phases of the proposed research. The material collected during this project will set the stage for significant future research. LacCore, the National Lacustrine Core Facility at the University of Minnesota, will facilitate this by overseeing the long-term storage, curation, and access to data and samples obtained in this project.Technical Explanation Lake Junin, located at 4000 m asl in the inner-tropics of the Southern Hemisphere, is a prime target for drilling because it contains a thick (200 m) sediment package deposited at a high rate (0.2 to 1.0 mm/yr). Abundant research conducted on and around Lake Junin provides a compelling rationale for deep drilling. Moraine mapping coupled with cosmogenic radionuclide dating indicate that paleoglaciers reached the lake edge, but have not overridden the lake in as much as one million years. Lake Junin is one of the few lakes in the tropical Andes that predates the maximum extent of glaciation and is in a geomorphic position to record the waxing and waning of glaciers in nearby cordillera. Sediment coring of Lake Junin began in the 1970s; two cores spanning the past 50,000 years reveal that sedimentation has alternated between clastic sediments deposited during peak glacial periods and authigenic calcite (marl) precipitated from the water column during interglacial times. The lake also contains ideal sediments for multiproxy analysis that can be reliably dated using both the radiocarbon and U/Th methods. The oxygen isotopic composition of marl and ostracod carapaces demonstrate that authigenic calcite in Lake Junin primarily records the isotopic composition of precipitation and secondarily the degree of evaporative enrichment of lake water. Lake Junin contains a continuous record of tropical hydroclimate over interglacial and interstadial intervals for much of the past several hundred thousand years that is both comparable to, and an extension of stable isotope records from regional ice cores and speleothems. New organic geochemical proxies compliment the marl isotope record and offer the potential for a truly continuous isotope paleoclimate record through glacial and interglacial intervals alike. Lake Junin is ideally situated, both from logistical and scientific standpoints, to provide continuous high-resolution, independently-dated, long-term records of glaciation, and the variability of phenomena such as ENSO, the South America Summer Monsoon, and the Intertropical Convergence Zone. Because of the strong, demonstrated U/Th dating potential of Junin marl, we will be able to address critical issues regarding the synchrony of climate change in the tropics with that in high latitude regions of both hemispheres, the rate and timing of ecosystem response to climatic perturbations, and the dynamics of the geomagnetic field from a tropical perspective. Lake Junin is a scientifically mature site that will yield critical scientific insights that only drilling coupled with analysis can unlock.The primary objective of the proposed research is to develop the first continuous, high-resolution, absolute-dated late Quaternary record of climate change, water balance (P/E), glaciation, vegetation, and paleomagnetic secular variation for the tropical Andes. The well-dated Junin record will allow the team to develop proxy records spanning 200,000yr, which will document the timing of wet/dry cycles, glacial advances/retreats, and the impacts of climatic phenomena such as the changing strength and variability of ENSO, the South America Summer Monsoon, and shifts in the location and range of the Intertropical Convergence Zone. In addition, this study will provide an opportunity to date (via U-Th) the 40ka sections of both the Titicaca and Sabana de Bogota records through correlation of pollen, stable isotope, and paleomagnetic time series. This study will also enable important insights into the response of tropical vegetation to climate change in the upper Amazon Basin, and will provide a rare southern equatorial perspective on the evolution of Earth?s geomagnetic field.

要了解气候变化的全部复杂性并预测未来的区域趋势，我们就必须将现有的仪器记录扩展到过去的地质时期。在过去的几十年里，古气候学家开发了无数的过去区域气候的代用指标，这些指标记录在冰芯、洞穴沉积物、湖泊沉积物等许多自然档案中。热带地区的代用古气候记录尤为重要，因为该地区是？热引擎?地球的。在厄尔尼诺-南方涛动（ENSO）、热带辐合带的平均位置以及热带对高纬度气候事件的响应等现象中表现出来的海洋-大气环流的长期和短期变化。理解这些现象至关重要，因为这些现象会对区域水平衡产生深远影响，直接影响到饮用水供应、水力发电和农业生产力。热带地区气候变化的最长连续记录仅限于那些来自该地区相对较少的古老湖泊盆地的记录。朱宁湖是秘鲁境内最大的湖泊，也是南美洲最古老的湖盆之一。它包含了至少200米长的沉积物记录，可能超过25万年。朱宁湖的独特之处在于它所包含的记录长度，以及它所记录的气候信号。大量前期研究表明，通过湖底沉积的碳酸钙同位素地球化学特征，Junin湖以大约0.2 ~ 1.0 mm/yr的速率记录了附近高山冰川的盛衰和区域水平衡的变化。这项研究将为恢复的岩心的整个长度发展这些和其他代用气候记录；生成的记录将包括从内热带地区持续时间最长的气候和环境变化记录之一。Junin湖钻探项目有几个更广泛的影响。其中包括对废弃小屋的联合翻新，以供未来共享使用，作为Junin国家保护区官员的第一个海岸线前哨，作为游客中心，以及作为生态旅游的湖泊入口。朱宁项目的能力建设活动包括与秘鲁大学合作，培训地球科学家，以及培训秘鲁和美国的学生。一个专门的小组将负责在该地区的村庄组织讲座，向市民宣传钻探的重要性，并将与国家公园管理局密切合作，指导护林员如何利用科学来促进湖周围的保护工作。在钻井过程中，一个团队将促进与当地和国际媒体的互动。该团队希望让美国和秘鲁的学生参与朱宁钻探的各个方面，而与朱宁岩心有关的大部分古生态学研究将由研究生进行。还计划在作业的钻探阶段为秘鲁各大学的地球科学家提供培训机会。众多美国本科生和研究生以及一名博士后将参与拟议研究的各个阶段。在这个项目中收集的材料将为未来的重要研究奠定基础。明尼苏达大学的国家湖泊核心设施LacCore将通过监督该项目中获得的数据和样本的长期存储、管理和访问来促进这一工作。Junin湖位于海拔4000米的南半球内热带地区，是钻井的主要目标，因为它含有厚（200米）的沉积物包，沉积速度快（0.2至1.0毫米/年）。在Junin湖及其周围进行的大量研究为深钻提供了令人信服的理由。冰碛测绘加上宇宙形成的放射性核素年代测定表明，古冰川到达了湖泊边缘，但在长达100万年的时间里没有覆盖湖泊。朱宁湖是热带安第斯山脉为数不多的几个在冰川最大程度之前就存在的湖泊之一，它所处的地理位置可以记录附近科迪勒拉冰川的盛衰。君宁湖沉积物取芯始于20世纪70年代；过去5万年的两个岩心表明，沉积在冰期高峰沉积的碎屑沉积物和间冰期水柱沉淀的自生方解石（泥灰岩）之间交替发生。该湖泊还包含理想的沉积物，可以使用放射性碳和U/Th方法可靠地进行多代理分析。泥灰岩和介形虫甲壳的氧同位素组成表明，君宁湖自生方解石主要记录降水的同位素组成，其次记录湖水的蒸发富集程度。Junin湖包含了过去几十万年大部分间冰期和间冰期热带水文气候的连续记录，这些记录与区域冰芯和洞穴的稳定同位素记录相当，并且是其扩展。新的有机地球化学指标补充了泥灰岩同位素记录，并提供了通过冰期和间冰期进行真正连续的同位素古气候记录的潜力。从后勤和科学的角度来看，Junin湖的地理位置非常理想，可以提供连续的高分辨率、独立日期的冰川作用和ENSO、南美洲夏季风和热带辐合带等现象的变化记录。由于Junin泥灰岩具有强大的U/Th定年潜力，我们将能够从热带的角度解决热带地区与两个半球高纬度地区气候变化的同步性、生态系统对气候扰动的响应速度和时间以及地磁场的动力学等关键问题。Junin湖是一个科学成熟的地点，将产生关键的科学见解，只有钻井和分析才能解开。该研究的主要目标是为热带安第斯山脉建立第一个连续的、高分辨率的、绝对年代的晚第四纪气候变化、水平衡（P/E）、冰川作用、植被和古地磁长期变化的记录。年代久远的朱宁记录将使研究小组能够开发出跨越20万年的代用记录，这些记录将记录湿/干循环的时间、冰川前进/后退的时间，以及气候现象的影响，如ENSO的变化强度和可变性、南美夏季风、热带辐合带的位置和范围的变化。此外，本研究将通过花粉、稳定同位素和古地磁时间序列的对比，为Titicaca和Sabana de Bogota的40ka剖面记录的测年（通过U-Th）提供机会。这项研究还将对亚马逊河上游热带植被对气候变化的响应提供重要见解，并将为地球演化提供罕见的南赤道视角。S地磁场。