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: 1405546
• 负责人: Matthew Lachniet
• 金额: $ 33.45万
• 依托单位: University of Nevada Las Vegas
• 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=1405546&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.

气候科学家长期以来一直记录了地球轨道变化对冰河时代的盈亏的强烈控制。30年前，内华达州魔鬼洞的一个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一致，在地球轨道变化的预期之前，冰川期后的气候变暖。现在，新的证据表明，大盆地的气候变化与轨道变化同步，并表明在过去的17.5万年里，随着夏季到达北方半球的太阳辐射量的增加，气候变暖和变冷。来自大盆地洞穴的放射性测年石笋有可能将记录追溯到50万年前。这些洞穴沉积物记录了洞穴遗址上方和上风处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，并将允许与太平洋的海面温度记录和魔鬼洞方解石记录进行比较。该项目还将促进根据已知的未来轨道变化对美国西南部进行长期气候预测。总体假设，将在这个项目的过程中进行测试的是，西南部的古气候变化的节奏Milankovitch（轨道）强迫，通过变化，在北方半球夏季日照改变大气环流动力学在东北太平洋地区。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50万年来北方半球夏季日照变化一致。氧同位素分析将在内华达州拉斯维加斯大学进行，铀不平衡测年将在新墨西哥州大学进行。研究小组将包括来自两个主要机构以及本科生服务机构康奈尔学院（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，与当地洞穴探险团体和政府机构分享。