Collaborative Research: Calibrating the paleosol carbonate CO2 barometer for vertic paleosols by monitoring soil CO2 in modern Vertisols

合作研究：通过监测现代变性土中的土壤二氧化碳来校准垂直古土壤的古土壤碳酸盐二氧化碳气压计

• 批准号: 0922131
• 负责人: Daniel Breecker
• 金额: $ 19.52万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-08-15 至 2013-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0922131&HistoricalAwards=false
• 关键词: Collaborative; Research; Calibrating; paleosol; carbonate

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Intellectual Merit: A calibration of the paleosol carbonate CO2 barometer is proposed in order to improve estimates of the concentration of CO2 in Earth?s ancient atmosphere. The concentration of CO2 in the soil during soil carbonate formation, S(z), is required in order to calculate atmospheric CO2 concentrations using the barometer. Recent research has shown that the value of S(z) in desert soils is significantly lower than values typically used in the barometer because carbonate does not form under mean growing season conditions as previously assumed but instead forms during times of year when the soil is sufficiently dry to limit respiration (i.e. soil CO2 production). Atmospheric CO2 levels that are significantly lower than previously reported (~1000 ppmV versus ~3000 ppmV) result if the seasonally low S(z) value determined for desert soils is used to calculate atmospheric CO2 concentrations from previously compiled paleosol data. The persistence of greenhouse climates (warm, ice-free Earth) under these relatively low CO2 concentrations suggests that the Earth?s surface temperature is much more sensitive to atmospheric CO2 than currently thought. A thorough evaluation of this possibility requires further study because desert soils are not the most appropriate modern analog for most paleosols used in paleoatmospheric CO2 studies. The proposed study is intended to constrain S(z) in modern Vertisols, which are high clay-content, high shrink-swell potential soils. Vertisols are chosen for this study because their ancient equivalents have been widely used to reconstruct ancient atmospheric CO2. The following three-part hypothesis will be tested: 1) drying of the soil reduces respiration rates, 2) cracking of the soil (when it is dry) allows respired CO2 to escape from the soil more rapidly and 3) the decrease in soil CO2 concentration resulting from both drying and cracking causes the formation of pedogenic carbonate in Vertisols. A suite of measurements will be carried out in Texas Vertisols to determine what portion of seasonal variability pedogenic carbonate records. The concentration of soil CO2, the stable isotope composition of soil CO2, soil temperature and soil moisture will be monitored and the stable isotope composition of pedogenic carbonate in the soil will be measured. The timing of pedogenic carbonate formation, and by association the most appropriate value(s) for S(z), will be determined based on when isotope equilibrium between soil CO2 and carbonate occurs and when minimum calcite solubility occurs. If the value(s) determined for S(z) are significantly different than those used in previous studies, the new values will be used to recalculate paleoatmospheric CO2 concentrations and to estimate climate sensitivity from Paleozoic and Mesozoic paleo-Vertisols. Broader Impacts: Predicting the severity of the impending climate crisis is one of the most important scientific challenges facing humanity today. The proposed research directly addresses this challenge by reevaluating the sensitivity of Earth?s climate to elevated atmospheric CO2 concentrations. Therefore, the broadest impacts of the proposed research will be to help predict future climate change and to help inform policy makers about the potential consequences of continued, unmitigated anthropogenic CO2 emissions. Personal edification, ranging from the mutual intellectual benefits of collaborative research to graduate and undergraduate education to public outreach in various venues, will have a more immediate and individual impact.

该奖项是根据2009年的《美国回收与再投资法》（公法111-5）进行的。智能优点：提出了对古碳酸盐二氧化碳元水计的校准，以提高地球上二氧化碳浓度的估计。为了使用晴雨表计算大气中的二氧化碳浓度，需要在土壤形成碳酸盐形成过程中土壤中二氧化碳的浓度。最近的研究表明，沙漠土壤中S（Z）的值明显低于晴雨表中通常使用的值，因为碳酸盐在平均生长季节条件下不如前所述，而是在土壤充分干燥以限制呼吸以限制呼吸（即土壤CO2产量）的时间中形成。大气中的二氧化碳水平明显低于先前报道的（〜1000 ppmv vess 〜3000 ppmv），如果确定沙漠土壤的季节性低s（z）值来计算先前收集的古溶胶数据中的大气二氧化碳浓度。在这些相对较低的二氧化碳浓度下，温室气候（温暖，无冰的土）的持久性表明，地球表面温度对大气二氧化碳的敏感性比目前想象的要敏感得多。对这种可能性进行彻底的评估需要进一步研究，因为沙漠土壤不是paaotopheric CO2研究中大多数古溶质的最合适的现代类似物。拟议的研究旨在限制现代的垂直溶质中的S（Z），这些垂直溶质是高粘土，高收缩的潜在土壤。为此研究选择了Vertisols，因为它们的古代等效物已被广泛用于重建古老的大气二氧化碳。将测试以下三部分假设：1）土壤干燥降低呼吸率，2）土壤的开裂（干燥时）允许呼吸二氧化碳可以更快地从土壤中逸出，而3）土壤二氧化碳浓度降低，导致干燥和破裂因vertisols中的成碳酸盐的形成而导致的。在德克萨斯州的垂tisols中将进行一系列测量，以确定季节性变异性碳酸盐记录的哪些部分。将监测土壤二氧化碳，土壤二氧化碳，土壤温度和土壤水分的稳定同位素组成的浓度，并将测量土壤中稳定的同位素组成。根据土壤二氧化碳和碳酸盐之间的同位素平衡以及何时发生最小的方解石溶解度，将确定S（Z）的最适当值（S（Z）的最合适值）的时间。如果针对S（Z）确定的值与以前的研究中使用的值显着不同，则新值将用于重新计算peaotospheric CO2浓度，并估计与古生代和中生代古杂质醇的气候灵敏度。更广泛的影响：预测即将到来的气候危机的严重性是当今人类面临的最重要的科学挑战之一。拟议的研究通过重新评估地球气候对升高大气二氧化碳浓度的敏感性直接解决了这一挑战。因此，拟议的研究的最广泛影响是帮助预测未来的气候变化，并帮助政策制定者了解持续，不受限制的人为CO2排放的潜在后果。个人教育，从合作研究的相互智力益处到研究生和本科教育到在各个场所的公共宣传，都将产生更直接和个人的影响。