RPG: Stable Oxygen and Hydrogen Isotope Studies of Groundwater and Wood from the Last Glacial Maximum to the Present

RPG：从末次盛冰期至今地下水和木材的稳定氧和氢同位素研究

• 批准号: 9506752
• 负责人: Xiahong Feng
• 金额: $ 1.8万
• 依托单位: Dartmouth College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-09-01 至 1997-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9506752&HistoricalAwards=false
• 关键词: RPG; Stable; Oxygen; Hydrogen; Isotope

ABSTRACT EAR-9506752 Feng A commonly used climatic indicator in continental paleoclimatic studies is inferred oxygen and hydrogen isotopic compositions of paleometeoric water either by direct measurements, such as polar ice, or by using proxy indicators, such as lake sediments, soil carbonates, cave deposits, vein calcite, and tree rings. Because climatic indicators are rarely single-variable functions of meteoric water, the climatic reconstructions are not always consistent. In particular, groundwater samples dating back to the Last Glacial Maximum are typically depleted in deuterium relative to worldwide Holocene recharge, while waters inferred from wood cellulose is typically enriched in deuterium. This project attempts to resolve the cause(s) and mechanisms of this observational discrepancy. The main approach is to locate meteoric recharge zones known to be responsible for some of the paleogroundwaters that have been described, and find and analyze wood samples known to have grown in the same area. If the disagreement between Pleistocene groundwater and Pleistocene wood is confirmed, then it may imply fundamental differences in climatic parameters between the Last Glacial Maximum and the Holocene. Emphasis during the Planning Grant will be placed on finding appropriate sites for the study. The focus will be on the north-central and central U.S, where paleogroundwater and ancient wood samples are well documented, and North China, where Pleistocene water is widely distributed. Because the discrepancy between groundwater and wood is a large-scale observation, the causes must be large scale phenomena. Thus, this project should make fundamental contributions to the understanding of the climate and environment.

大陆古气候研究中常用的一个气候指标是通过直接测量，如极地冰，或通过代理指标，如湖泊沉积物、土壤碳酸盐、洞穴沉积物、脉方解石和树木年轮来推断古大气水的氧和氢同位素组成。由于气候指标很少是大气水的单变量函数，因此气候重建并不总是一致的。特别是，与全球全新世的补给相比，追溯到末次盛冰期的地下水样本通常缺乏氘，而从木材纤维素推断的水通常富含氘。本项目试图解决这种观测差异的原因和机制。主要的方法是找到已知的对某些已描述的古地下水负责的大气补给区，并找到并分析已知生长在同一地区的木材样本。如果更新世地下水和更新世木材的差异得到证实，则可能意味着末次盛冰期和全新世的气候参数存在根本差异。规划补助金的重点是为研究寻找合适的地点。重点将放在美国中北部和中部，那里的古地下水和古代木材样本被很好地记录下来，以及华北，那里的更新世水分布广泛。由于地下水与木材的差异是大尺度观测，其原因必然是大尺度现象。因此，这个项目应该对了解气候和环境做出根本性的贡献。