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: 1404113
• 负责人: Mark Abbott
• 金额: $ 62万
• 依托单位: University of Pittsburgh
• 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=1404113&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.

我们了解气候变化的全部复杂性并预测未来区域趋势的能力要求我们将可用的仪器记录扩展到地质历史。在过去的几十年里，古气候学家开发了无数过去区域气候的代理指标，这些指标记录在自然档案中，例如冰芯、洞穴沉积物和湖泊沉积物以及许多其他档案中。来自热带地区的代理古气候记录尤其重要，因为该地区是“热机”。地球的。海洋-大气环流的长期和短期变化，表现为厄尔尼诺南方涛动（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。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，从而直接影响饮用水供应、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该地区相对较少的老湖盆地的记录。胡宁湖是完全位于秘鲁境内的最大湖泊，是南美洲最古老的湖盆之一。它包含至少 200 m 长的沉积物记录，可能持续超过 250,000 年。胡宁湖的独特之处在于它所包含的记录长度，而且还在于它记录的气候信号。大量先前的研究已证明，胡宁湖通过湖底碳酸钙的同位素地球化学以每年约 0.2 至 1.0 毫米的速度沉积，记录了附近高山冰川的增减以及区域水平衡的变化。这项研究将为回收的岩心的全长开发这些和其他代理气候记录；生成的记录将包括内热带气候和环境变化最长的连续记录之一。 胡宁湖钻探项目有几个更广泛的影响。其中包括联合翻修一座废弃的小屋，以供未来共享，作为胡宁国家保护区官员的第一个海岸线前哨站、游客中心以及生态旅游的湖泊入口点。胡宁项目的能力建设活动包括与秘鲁大学的合作、地球科学家的培训以及秘鲁和美国学生的培训。一个专门的团队将负责在该地区的村庄组织讲座，让公民了解钻探的重要性，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周围的保护工作湖。在演习期间，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学生参与胡宁钻探的各个方面，与胡宁岩心相关的大部分古生态研究将由研究生进行。 还计划为秘鲁大学的地球科学家提供钻井作业阶段的培训机会。许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所有阶段。 该项目期间收集的材料将为未来的重要研究奠定基础。 LacCore 是明尼苏达大学的国家湖泊核心设施，将通过监督长期存储、管理以及对本项目中获得的数据和样本的访问来促进这一目标。 技术说明 胡宁湖位于内陆海拔 4000 米处- 南半球热带地区是钻探的主要目标，因为它包含厚（200 m）的沉积物包，沉积速度很高（0.2 至 1.0毫米/年）。在胡宁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。冰碛测绘与宇宙成因放射性核素测年相结合表明，古冰川到达了湖边，但在长达一百万年的时间里还没有覆盖湖泊。胡宁湖是热带安第斯山脉中为数不多的早于最大程度的冰川作用的湖泊之一，其地貌位置可以记录附近山脉冰川的增减。胡宁湖沉积物取芯工作始于 20 世纪 70 年代；跨越过去5万年的两个岩心显示，沉积作用在冰川高峰期沉积的碎屑沉积物和间冰期从水柱中沉淀的自生方解石（泥灰岩）之间交替进行。该湖还含有适合多重代理分析的理想沉积物，可以使用放射性碳和 U/Th 方法可靠地测定年代。泥灰岩和介形类甲壳的氧同位素组成表明，胡宁湖的自生方解石主要记录了降水的同位素组成，其次记录了湖水的蒸发富集程度。胡宁湖包含了过去数十万年大部分时间里冰间和间质热带水文气候的连续记录，这既可与区域冰芯和洞穴的稳定同位素记录相媲美，又是其延伸。新的有机地球化学代理补充了泥灰岩同位素记录，并提供了通过冰期和间冰期间隔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，胡宁湖地理位置优越，可以提供连续的高分辨率、独立日期的长期冰川作用记录以及ENSO、南美夏季季风和热带辐合等现象的变化区。由于胡宁泥灰岩具有强大的、已证实的 U/Th 测年潜力，我们将能够解决有关热带地区与两个半球高纬度地区气候变化同步性、生态系统对气候变化的响应速度和时间等关键问题。气候扰动，以及从热带角度看地磁场的动态。胡宁湖是一个科学上成熟的地点，将产生只有钻探和分析才能解锁的关键科学见解。拟议研究的主要目标是开发第一个连续的、高分辨率的、绝对日期的晚第四纪气候变化记录，热带安第斯山脉的水平衡（P/E）、冰川作用、植被和古地磁长期变化。日期明确的胡宁记录将使团队能够开发跨越 20 万年的代理记录，其中将记录干湿循环的时间、冰川前进/后退以及气候现象的影响，例如 ENSO 强度和变异性的变化，南美洲夏季风，以及热带辐合带位置和范围的变化。此外，这项研究将提供一个机会，通过花粉、稳定同位素和古地磁时间序列的关联来确定（通过 U-Th）的的喀喀湖和萨巴纳波哥大记录的 40ka 剖面的年代。这项研究还将有助于深入了解亚马逊盆地上游热带植被对气候变化的反应，并将为地球地磁场的演变提供罕见的南赤道视角。