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

加州气候的仪器记录可以追溯到大约100年前，而且长度太短，无法捕捉到该州温度和降水的全部自然变化。该项目将提供12000多年前的气候变化记录。该项目将分析蚊幼虫化石（Chironomids）、甲壳类动物化石（Cladocera）、单细胞水生藻类化石（硅藻）、陆生植物微化石，以及来自内华达山脉东部湖泊沉积物的地球化学证据，以重建12000多年前的温度和有效湿度记录。通过湖泊沉积物中有机物的放射性碳定年，将年代学与记录联系起来。以前的工作已经开发了数学模型，可以从化石chironomid和硅藻组合中提供过去温度和有效湿度的数值估计。先前的初步工作还恢复了几个湖泊沉积物记录，这些记录可以追溯到11,000年前，并清楚地表明，在12,000至9,000年前从冰川到现代气候条件的过渡期间，温度和有效湿度的高频和低频变化。本项目将完成对这些核心剖面的分析。然后，该项目将使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来重建过去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区建立超过50年时间分辨率的记录。除了在冰川期到非冰川期的转变中看到的几百年到几千年的显著变化外，该项目还将利用以前发表的过去2000年的数据来发现过去9000年里几十年到几百年的干旱的证据。将加利福尼亚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盖的岩心中明显的变率时间模式进行比较，以帮助推断加利福尼亚气候长期变率的更大尺度原因。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、温暖期和寒冷期的严重程度和持续时间的全面变化至关重要。这些记录将有助于确定诸如几十年一次的干旱等现象是否存在长期周期性，从而使此类事件更容易预测。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方面的作用。最后，该项目提供的长期气候记录将提供加利福尼亚气候自然变化的基线数据，这将允许检测可能归因于温室变暖的真正不寻常的变化。这些记录将对水资源管理、林业和保护管理以及气候变化检测和管理具有重要意义。

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.