Collaborative Research: Ice sheet erosional interaction with hot geotherm in West Antarctica

合作研究：南极洲西部冰盖侵蚀与热地温的相互作用

• 批准号: 1916982
• 负责人: Christian Teyssier
• 金额: $ 17.22万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-08-01 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1916982&HistoricalAwards=false
• 关键词: Collaborative; Research; Ice; sheet; erosional

Sediment records off the coast of Marie Byrd Land (MBL), Antarctica suggest frequent and dramatic changes in the size of the West Antarctic Ice Sheet (WAIS) over short (tens of thousands of years) and long (millions of years) time frames in the past. WAIS currently overrides much of MBL and covers the rugged and scoured bedrock landscape. The ice sheet carved narrow linear troughs that reach depths of two to three thousand meters below sea level as outlet glaciers flowed from the interior of the continent to the oceans. As a result, large volumes of fragmented continental bedrock were carried out to the seabed. The glaciers cut downward into a region of crystalline rocks (i.e. granite) whose temperature change as a function of rock depth happens to be significant. This strong geothermal gradient in the bedrock is favorable for determining when the bedrock experienced rapid exhumation or "uncovering". Analyzing the chemistry of minerals (zircon and apatite) within the eroded rocks will provide information about the rate and timing of the glacier removal of bedrock from the Antarctic continent. The research addresses the following questions: When did the land become high enough for a large ice sheet to form? What was the regional pre-glacial topography? Under what climate conditions, and at what point in the growth of an ice sheet, did glaciers begin to cut sharply into bedrock to form the narrow troughs that flow seaward? The research will lead to greater understanding of past Antarctic ice sheet fluctuations and identify precise timing of glacial incision. These results will refine ice sheet history and aid the international societal response to contemporary ice sheet change and its global consequences. The project will contribute to the training of two graduate and two undergraduate students in STEM.The objective is to clarify the onset of WAIS glacier incision and assess the evolution of Cenozoic paleo-topography. Low-temperature (T) thermochronology and Pecube 3-D thermo-kinematic modeling will be applied to date and characterize episodes of glacial erosional incision. Single-grain double- and triple-dating of zircon and apatite will reveal the detailed crustal thermal evolution of the region enabling the research team to determine the comparative topographic influences on glaciation versus bedrock uplift induced by Eocene to present tectonism/magmatism. High-T mineral thermochronometers across Marie Byrd Land (MBL) record rapid extension-related cooling at ~100 Ma from temperatures of 800 degrees C to ≤ 300 degrees C. This signature forms a reference horizon, or paleogeotherm, through which the Cenozoic landscape history using low-T thermochronometers can be explored. MBL's elevated geothermal gradient, sustained during the Cenozoic, created favorable conditions for sensitive apatite and zircon low-T thermochronometers to record bedrock cooling related to glacial incision. Students will be trained to use state-of-the-art analytical facilities in Arizona and Minnesota, expanding the geo- and thermochronologic history of MBL from bedrock samples and offshore sedimentary deposits. The temperature and time data they acquire will provide constraints on paleotopography, isostasy, and the thermal evolution of MBL that will be modeled in 3D using Pecube model simulations. Within hot crust, less incision is required to expose bedrock containing the distinct thermochronometric profile; a prediction that will be tested with inverse Pecube 3-D models of the thermal field through which bedrock and detrital samples cooled. Using results from Pecube, the ICI-Hot team will examine time-varying topography formed in response to changes in erosion rates, topographic relief, geothermal gradient and/or flexural isostatic rigidity. These effects are manifestations of dynamic processes in the WAIS, including ice sheet loading, ice volume fluctuations, relative motion upon crustal faults, and magmatism-related elevation increase across the MBL dome. The project makes use of pre-existing sample collections housed at the US Polar Rock Repository, IODP's Gulf Coast Core Repository, and the Antarctic Marine Geology Research Facility.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Sediment记录了玛丽·伯德（Marie Byrd）沿海（MBL）的海岸，南极洲表明，过去（数十千年）和长期（数百万年）的时间范围内，南极冰盖（WAIS）的大小频繁而急剧变化。 WAI目前覆盖了MBL的大部分，并覆盖了崎and的岩石岩石景观。当出口冰川从大陆的内部流到海洋，冰板雕刻了狭窄的线性槽，到达海平面两到三千米的深度。结果，在海床上进行了大量零散的大陆基岩。冰川向下切入了晶体（即花岗岩）的区域，其温度随岩石深度的变化而变化恰好是显着的。基岩中这种强大的地热梯度有利于确定基岩何时经历快速发掘或“揭开”。分析被侵蚀的岩石中矿物质（锆石和磷灰石）的化学性质将提供有关从南极洲大陆冰川去除基岩的速率和时机的信息。该研究解决了以下问题：何时将土地变得足够高，以使大型冰盖形成？区域前冰期地形是什么？在什么气候条件下，在冰盖生长的什么时候，冰川开始急剧切入基岩以形成向海流动的狭窄谷？这项研究将使对过去南极冰盖波动的了解更加了解，并确定冰川切口的精确时机。这些结果将完善冰原历史，并帮助国际社会对当代冰盖变化及其全球后果的反应。该项目将有助于培训两名研究生和两名本科生的STEM。目的是阐明Wais冰川切口的发作并评估新生代古读术的演变。低温（T）热量体学和PECUBE 3-D热旋化建模将于迄今为止应用，并表征冰川侵蚀切口的发作。锆石和磷灰石的单颗粒双重和三重年代将揭示该区域的详细地壳热演化，从而使研究团队能够确定对晶状体诱导的冰川升高的比较地形影响，以表现构造/岩浆作用。玛丽·伯德（Marie Byrd）土地（MBL）的高矿物热化学计记录了与800摄氏度至＆＃8804摄氏度的快速延伸相关冷却〜100 mA。 300度C.该签名形成了参考范围或古植物，可以探索使用低T热化学计的培根景观历史记录。 MBL在新生代期间维持的高度地热梯度为敏感的磷灰石和氧化锆低T热化学计创造了有利的条件，以记录与冰川切口相关的基岩冷却。学生将接受培训，可以在亚利桑那州和明尼苏达州使用最先进的分析设施，从而扩大了基岩样品和近海沉积沉积物中MBL的地理和热量学历史。他们获取的温度和时间数据将对古代摄影，等法性和MBL的热演化提供约束，该MBL将使用Pecube模型模拟在3D建模。在Hot Crust中，需要更少的切口才能露出包含不同热化学轮廓的基岩；一个预测，将通过逆Pecube 3-D模型的热场进行测试，基岩和碎屑样品冷却。利用Pecube的结果，ICI热团队将检查根据侵蚀率的变化，地形浮雕，地热梯度和/或弯曲等静力刚性刚性而形成的时变地形。这些效果是WAI中动态过程的表现，包括冰盖载荷，冰的体积波动，地壳断层上的相对运动以及MBL圆顶上与岩浆作用相关的高程增加。该项目利用在美国极地岩石存储库，IODP的墨西哥湾沿岸核心存储库和南极海洋地质研究设施中存放的样本集，该奖项反映了NSF的法定任务，并被认为是通过基金会的智力和更广泛影响的评估来评估的支持。