High Resolution Time-Series of California Climate Over the Last 12,000 Years: Examining the Linkage with the North Atlantic and North Pacific

过去 12,000 年加州气候的高分辨率时间序列：检查与北大西洋和北太平洋的联系

• 批准号: 0135748
• 负责人: Glen MacDonald
• 金额: $ 12.47万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-04-01 至 2004-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0135748&HistoricalAwards=false
• 关键词: Resolution; Time; Series; California; Climate

Instrumental records of climate in California extend back approximately 100 years and are too short in length to capture the full range of natural variability of temperature and precipitation in the state. The project will provide records of climatic variability that extend back over 12,000 years. The project will analyze fossil midge fly larva (Chironomids), crustaceans (Cladocera), unicellular aquatic algae (diatoms), terrestrial plant microfossils, and geochemical evidence from lake sediments from the eastern Sierra Nevada to reconstruct records of temperature and effective moisture that extend back over 12,000 years. Chronologies will be linked to the records by the radiocarbon dating of organic matter in the lake sediments. Previous work has developed mathematical models that provide numerical estimates of past temperature and effective moisture from fossil chironomid and diatom assemblages. Previous preliminary work has also led to the recovery of several lake sediment records that extend back past 11,000 years in age and show clear evidence of both high and low frequency changes in temperature and effective moisture during the transition from glacial to modern climatic conditions between 12,000 and 9000 years ago. This project will complete analysis of these core sections. The project will then use the existing lake sediment cores and new cores collected from climatically sensitive settings to reconstruct changes in temperature and effective moisture over the past 9000 years. The project will construct records with better than 50 year temporal resolution for both high and mid-elevation sites. In addition to the significant multi-centennial to millennial variations seen in the glacial to non-glacial transition, the project will use previously published data for the past 2000 years to uncover evidence of multi-decadal to multi-centennial droughts during the past 9000 years. The temporal patterns of variations in California temperature and effective moisture will be compared to temporal patterns of variability evident in cores from the North Pacific Ocean, North Atlantic Ocean and Greenland Ice Cap, in order to help deduce the larger scale causes of long-term variability in California climate. Long-term climate records are essential to anticipating the full range of variability in the severity and duration of long-term drought periods, wet periods and warm and cold periods that can occur in California. The records will help determine if there is long-term periodicity in phenomena such as multi-decadal droughts that will make such events more predictable. These records of past climate will also help in assessing the role of changes in the Atlantic and Pacific oceans in driving climatic variations in California. Finally, the long-term climatic records provided by this project will furnish baseline data on natural variability of climate in California that will allow for the detection of truly unusual variations that might be attributable to greenhouse warming. The records will be of importance for water resource management, forestry and conservation management, and climatic change detection and management.

加州的气候仪器记录可以追溯到大约100年前，而且时间太短，无法全面反映该州温度和降水的自然变化。该项目将提供12 000多年前的气候变化记录。该项目将分析摇蚊幼虫（摇蚊）、甲壳类（枝角类）、单细胞水生藻类（硅藻）、陆生植物微体化石和来自内华达州东部山脉湖泊沉积物的地球化学证据，以重建12,000多年来的温度和有效湿度记录。通过对湖泊沉积物中的有机物进行放射性碳测年，将年表与记录联系起来。以前的工作已经开发了数学模型，提供过去的温度和有效的水分从化石摇蚊和硅藻组合的数值估计。先前的初步工作也导致了几个湖泊沉积物记录的恢复，这些记录可以追溯到11,000年前，并显示了12,000年至9000年前从冰川到现代气候条件过渡期间温度和有效湿度的高频率和低频率变化的明确证据。本项目将完成对这些核心部分的分析。然后，该项目将利用现有的湖泊沉积物岩心和从气候敏感环境中收集的新岩心，重建过去9000年来温度和有效湿度的变化。该项目将为高海拔和中海拔地点建立时间分辨率超过50年的记录。除了在冰川到非冰川的过渡中看到的数百年到千年的重大变化外，该项目还将使用过去2000年的数据来揭示过去9000年中数十年到数百年干旱的证据。 将加州温度和有效湿度变化的时间模式与北太平洋、北大西洋和格陵兰冰帽岩芯中明显的变化时间模式进行比较，以帮助推断出加州气候长期变化的更大尺度原因。 长期气候记录对于预测加州可能发生的长期干旱期、湿润期和温暖期和寒冷期的严重程度和持续时间的全部可变性至关重要。 这些记录将有助于确定诸如数十年干旱等现象是否存在长期周期性，从而使此类事件更易于预测。这些过去气候的记录也将有助于评估大西洋和太平洋的变化在推动加州气候变化中的作用。最后，该项目提供的长期气候记录将提供关于加州气候自然变化的基线数据，从而能够发现可能归因于温室变暖的真正不寻常的变化。这些记录对水资源管理、林业和养护管理以及气候变化探测和管理都很重要。