Collaborative Research: Testing the hypothesis of an orbital forcing of southwestern North America climate over the past 500,000 years

合作研究：检验过去 50 万年北美西南部气候轨道强迫的假设

• 批准号: 1405557
• 负责人: Yemane Asmerom
• 金额: $ 16.15万
• 依托单位: University of New Mexico
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-07-01 至 2018-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1405557&HistoricalAwards=false
• 关键词: Collaborative; Research; Testing; hypothesis; orbital

Climate scientists have long documented the strong control of Earth's orbital variations on the waxing and waning of the ice ages. Thirty years ago, an iconic climate record from Devils Hole, Nevada, seemed to suggest that Great Basin the climate of the Great Basin of the western United States was out of step with the orbital rhythm, warming after glacial periods before what would be expected from changes in the Earth's orbit. Now new evidence places Great Basin climate variations back in synchrony with orbital variations, and shows that climate warmed and cooled with the amount of solar radiation reaching the northern Hemisphere during summer over the last 175,000 years. Radiometrically-dated stalagmites from Great Basin caves have the potential extend the record back to 500,000 years before present. These cave deposits record variations in climate in a broad region over and upwind of the cave sites. As such, they are ideally suited to test for an orbital control on Great Basin climate, and will allow comparison to sea surface temperature records in the Pacific Ocean, and to the Devils Hole calcite record. This project will also facilitate long-term climate projections for the southwestern United States based on known future orbital variations. The overarching hypothesis that will be tested in the course of this project is that southwestern paleoclimatic change was paced by Milankovitch (orbital) forcing, through changes in northern hemisphere summer insolation altering atmospheric circulation dynamics over the northeastern Pacific Ocean region. The research team will generate high-resolution oxygen isotope analyses of precisely-dated stalagmites from caves across the Great Basin region, and determine whether or not oxygen isotope variations align with variations in northern hemisphere summer insolation over the past half million years. Oxygen isotopic analyses will be carried out at the University of Nevada Las Vegas, and uranium disequilibrium dating at the University of New Mexico. The research team will include several students from both lead institutions as well as an undergraduate-serving institution, Cornell College (Iowa). The researchers and students will also create cave educational materials for sharing with local caving groups and governmental agencies.

气候科学家早已记录了地球轨道变化对冰河时代盛衰的强烈控制。三十年前，来自内华达州魔鬼洞的标志性气候记录似乎表明，美国西部大盆地的气候与轨道节奏不同步，在冰川期之后变暖，早于预期的气候变暖。地球轨道的变化。现在，新证据表明大盆地气候变化与轨道变化重新同步，并表明过去 175,000 年夏季到达北半球的太阳辐射量导致气候变暖和变冷。大盆地洞穴中的石笋放射性测年法有可能将这一记录追溯到距今 50 万年前。这些洞穴沉积物记录了洞穴遗址上方和上风向的广阔区域的气候变化。因此，它们非常适合测试大盆地气候的轨道控制，并且可以与太平洋海面温度记录和魔鬼洞方解石记录进行比较。该项目还将促进基于已知的未来轨道变化对美国西南部的长期气候预测。在该项目过程中将测试的总体假设是，西南古气候变化是由米兰科维奇（轨道）强迫引起的，通过北半球夏季日照的变化改变了东北太平洋地区的大气环流动态。研究小组将对大盆地地区洞穴中精确年代的石笋进行高分辨率氧同位素分析，并确定氧同位素变化是否与过去50万年北半球夏季日照的变化一致。氧同位素分析将在内华达大学拉斯维加斯分校进行，铀不平衡测年将在新墨西哥大学进行。研究团队将包括来自领先机构和本科院校康奈尔学院（爱荷华州）的几名学生。研究人员和学生还将制作洞穴教育材料，以便与当地洞穴团体和政府机构分享。