SGER - Carbon cycle processes affected by ENSO and transitional SOI conditions: Development of a new geologic tool for using speleothems as a proxy for carbon cycle dynamics

SGER - 受 ENSO 和过渡性 SOI 条件影响的碳循环过程：开发一种新的地质工具，利用洞穴岩石作为碳循环动力学的代理

• 批准号: 0337836
• 负责人: Dork Sahagian
• 金额: $ 1.6万
• 依托单位: University of New Hampshire
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-08-15 至 2005-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0337836&HistoricalAwards=false
• 关键词: SGER; Carbon; cycle; processes; affected

ABSTRACTSGER - Carbon cycle processes affected by ENSO and transitional SOI conditions:Development of a new geologic tool for using speleothems as a proxy for carbon cycledynamics.Using high-resolution microsampling techniques for stable isotope analysis of speleothems from Belize, we found large fluctuations in stalagmite d13C values at inter-annual to sub-seasonal time scales. These results reveal a remarkably strong correlation between d13C values and recent El NiNo events. Discovery of this relation is puzzling in light of the absence of significant weather anomalies during El NiNo and La NiNa intervals for this area. d13C values of this stalagmite likely reflect changes in the overlying forest ecosystem carbon budget that are sensitive to subtle modifications of local weather related to ENSO. Preliminary work suggests that the stalagmite d13C variations reflect changes in important ecosystem processes such as soil pCO2 and/or soil-atmospheric CO2 flux. As such, speleothems may be used as a tool for exploring carbon cycle dynamics and their response to environmental conditions.Our discovery of the correlation of SOI and the geologic record of C isotopes raises anumber of questions. Does this record reveal a new source of interannual variability in the global carbon cycle due to ENSO through its effects on terrestrial biogeochemical systems? Does El NiNo produce a stress on the ecosystem that is reflected in isotopic fractionation? Is the source of the fractionation difference in the vegetation, in the soil, or in the groundwater? What process(es) within the ecosystem serve to amplify the magnitude of ENSO-related environmental changes and leads to their being transmitted by groundwater and recorded in stalagmites? Consequently, the specific objectives of this SGER project are to capture carbon isotopic composition of vegetation, litter, soil gas/moisture, ground water, and cave drip water during a neutral phase of SOI, to complement the samples already collected during the recent El NiNo. Compare the carbon isotopic analyses of El NiNo and transitional samples to constrain location of differences in isotopic fractionation (e.g. vegetation, soil respiration, etc.). This SGER project will serve to capture the brief transition between El NiNo and La NiNa conditions that is expected to occur during the summer of 2003. As such it is time-sensitive, as the next transition through neutral conditions will not occur for several years. We will collect samples from ambient air, vegetation, leaf litter, soil, soil gas and water, groundwater, rainwater, cave air, and drip water. U.S. import permits have been obtained as necessary for soil and vegetation samples. Results from this project will provide a neutral baseline that will enable us to explore how the cave carbon biogeochemical system responds to ENSO events and identify the biogeochemical mechanisms responsible for the ENSO signal preserved in the geologic record. Ultimately this proposed project will provide the basis for new insights into the relationships between terrestrial ecosystems, weather, the carbon cycle, and the geological record.

受ENSO和过渡性SOI条件影响的碳循环过程：开发一种新的地质工具，使用洞穴主题作为碳循环动力学的代理。利用高分辨率显微采样技术对伯利兹洞穴石笋进行稳定同位素分析，我们发现石笋d13C值在年际和亚季节时间尺度上有较大波动。这些结果揭示了d13C值与最近的厄尔尼诺事件之间具有非常强的相关性。鉴于该地区在厄尔尼诺和拉尼娜间隔期间没有明显的天气异常，这种关系的发现令人费解。该石笋的d13C值可能反映了上覆森林生态系统碳收支的变化，这些变化对与ENSO相关的当地天气的细微变化很敏感。初步研究表明，石笋d13C的变化反映了土壤pCO2和/或土壤-大气CO2通量等重要生态系统过程的变化。因此，洞穴主题可以作为探索碳循环动力学及其对环境条件响应的工具。我们对SOI和C同位素地质记录的相关性的发现提出了许多问题。这一记录是否揭示了ENSO通过其对陆地生物地球化学系统的影响而导致全球碳循环年际变化的新来源？厄尔尼诺现象是否会对生态系统产生压力，从而反映在同位素分馏中？分异的来源是植被、土壤还是地下水？生态系统中哪些过程有助于放大与enso相关的环境变化的幅度，并导致它们通过地下水传播并记录在石笋中？因此，SGER项目的具体目标是在SOI中性阶段捕获植被、凋落物、土壤气体/水分、地下水和洞穴滴水的碳同位素组成，以补充最近厄尔尼诺现象期间已经收集的样本。比较厄尔尼诺和过渡性样品的碳同位素分析，以确定同位素分馏（如植被、土壤呼吸等）差异的位置。这个SGER项目将用于捕捉预计在2003年夏季发生的厄尔尼诺和拉尼娜之间的短暂过渡。因此，它是时间敏感的，因为下一个通过中性条件的过渡将不会在几年内发生。我们将收集环境空气、植被、凋落叶、土壤、土壤气和水、地下水、雨水、洞穴空气和滴水的样本。土壤和植被样本已获得必要的美国进口许可。该项目的结果将提供一个中性基线，使我们能够探索洞穴碳生物地球化学系统如何响应ENSO事件，并确定地质记录中保存的ENSO信号的生物地球化学机制。最终，这个拟议中的项目将为陆地生态系统、天气、碳循环和地质记录之间的关系提供新的见解基础。