PECASE: Relative frequency and phase of extreme expansions of the Antarctic Ice Sheets during the late Neogene

PECASE：新近纪晚期南极冰盖极端扩张的相对频率和阶段

• 批准号: 0094078
• 负责人: Philip Bart
• 金额: $ 32.22万
• 依托单位: Louisiana State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-02-01 至 2007-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0094078&HistoricalAwards=false
• 关键词: PECASE; Relative; frequency; phase; extreme

PROPOSAL NO.: 0094078PRINCIPAL INVESTIGATOR: Bart, PhilipINSTITUTION NAME: Louisiana State University & Agricultural and Mechanical CollegeTITLE: CAREER: Relative frequency and phase of extreme expansions of the Antarctic Ice Sheets during the late NeogeneNSF RECEIVED DATE: 07/27/2000PROJECT SUMMARYExpansions and contractions of the Antarctic Ice Sheets (AISs) have undoubtedly had a profound influence on Earth's climate and global sea-level. However, rather than being a single entity, the Antarctic cryosphere consists of three primary elements: 1) the East Antarctic Ice Sheet (EAIS); 2) the West Antarctic Ice Sheet (WAIS); and 3) the Antarctic Peninsula Ice Cap (APIC). The distinguishing characteristics include significant differences in: 1) ice volume; 2) substratum elevation; 3) ice-surface elevation; and 4) location with respect to latitude. Various lines of evidence indicate that the AISs have undergone significant fluctuations in the past and that fluctuations will continue to occur in the future. The exact nature of the fluctuations has been the subject of many lively debates. According to one line of reasoning, the land-based EAIS has been relatively stable, experiencing only minor fluctuations since forming in the middle Miocene, whereas the marine-based WAIS has been dynamic, waxing and waning frequently since the late Miocene. According to an alternate hypothesis, the ice sheets advanced and retreated synchronously. These two views are incompatible. The first objective of this proposal is to compare the long-term past behavior of the WAIS to that of the EAIS and APIC. The fluctuations of the AISs involve many aspects (the frequency of changes, the overall magnitude of ice-volume change, etc.), and the activities proposed here specifically concern the frequency and phase of extreme advances of the ice sheet to the continental shelf. The project will build upon previous seismic-stratigraphic investigations of the continental shelves. These studies have clarified many issues concerning the minimum frequency of extreme expansions for the individual ice sheets, but some important questions remain. During the course of the project, the following questions will be evaluated.Question 1) Were extreme advances of the EAIS and WAIS across the shelf of a similar frequency and coeval? This evaluation is possible because the western Ross Sea continental shelf (Northern Basin) receives drainage from the EAIS, and the eastern Ross Sea (Eastern Basin) receives drainage from the WAIS. Quantitative analyses of the extreme advances from these two areas have been conducted by Alonso et al. (1992) and Bart et al. (2000), respectively. However, the existing single-channel seismic grids are incomplete and can not be used to determine the stratigraphic correlations from Northern Basin to Eastern Basin. It is proposed that high-resolution seismic data (~2000 kms) be acquired to address this issue.Question 2) Were extreme advances of the APIC across the shelf as frequent as inferred by Bart and Anderson (1995)? Bart and Anderson (1995) inferred that the APIC advanced across the continental shelf at least 30 times since the middle Miocene. This is significant because it suggests that the advances of the small APIC were an order of magnitude more frequent than the advances of the EAIS and WAIS. Others contest the Bart and Anderson (1995) glacial-unconformity interpretation of seismic reflections, and argue that the advances of the APIC were far fewer (i.e., Larter et al., 1997). The recent drilling on the Antarctic Peninsula outer continental shelf has sampled some but not all of the glacial units, but the sediment recovery was poor, and thus, the glacial history interpretation is still ambiguous. The existing high-resolution seismic grids from the Antarctic Peninsula contain only one regional strike line on the outer continental shelf. This is inadequate to address the controversy of the glacial-unconformity interpretation and the regional correlation of the recent ODP results. It is proposed that high-resolution seismic data (~1000 kms) be acquired in a forthcoming (January 2002) cruise to the Antarctic Peninsula to address these issues.The second objective of this project is 1) to expand the PI's effort to integrate his ongoing and the proposed experiments into a graduate-level course at LSU, and 2) to develop a pilot outreach program with a Baton Rouge public high school. The Louisiana Department of Education has adopted scientific standards that apply to all sciences. These standards reflect what 9th through 12th grade-level students should be able to do and know. The PI will target one of these standards, the Science As Inquiry Standard 1 Benchmark. The PI will endeavor to share with the students the excitement of conducting scientific research as a way to encourage the students to pursue earth science as a field of study at the university level.

提案编号： 0094078主要赞助者：巴特，菲律宾机构名称：路易斯安那州立大学农业和机械学院标题：职业：南极冰盖在新生代晚期极端扩张的相对频率和阶段接收日期：2000年7月27日项目总结南极冰盖（AIS）的扩张和收缩无疑对地球气候和全球海平面产生了深远的影响。然而，南极冰冻圈并不是一个单一的实体，而是由三个主要部分组成：1）东南极冰盖（EAIS）; 2）西南极冰盖（WAIS）; 3）南极半岛冰帽（APIC）。 其显著特征包括：1）冰量; 2）底层高程; 3）冰面高程; 4）相对于纬度的位置。各种证据表明，人工智能系统在过去经历了重大波动，未来将继续发生波动。波动的确切性质一直是许多激烈辩论的主题。根据一条推理路线，陆基EAIS相对稳定，自中新世中期形成以来只经历了轻微的波动，而海基WAIS自中新世晚期以来一直是动态的，经常起伏不定。根据另一种假设，冰盖的前进和后退是同步的。这两种观点是不相容的。本建议的第一个目标是比较WAIS与EAIS和APIC的长期过去行为。 AIS的波动涉及很多方面（变化的频率、冰量变化的总体幅度等），这里提议的活动具体涉及冰盖向大陆架极端推进的频率和阶段。该项目将以以前对大陆架进行的地震地层学调查为基础。这些研究已经澄清了许多关于个别冰盖极端扩张的最小频率的问题，但仍然存在一些重要的问题。在项目过程中，将评估以下问题：问题1）EAIS和WAIS的极端进展是否在大陆架上具有相似的频率和同时代？ 这一评价是可能的，因为西部罗斯海大陆架（北方盆地）接受来自EAIS的排水，东部罗斯海（东部盆地）接受来自WAIS的排水。Alonso等人（1992年）和Bart等人（2000年）分别对这两个领域的极端进展进行了定量分析。 然而，现有的单道地震网格不完整，不能用于确定从北方盆地到东部盆地的地层对比。有人建议获取高分辨率地震数据（~2000公里）来解决这个问题。问题2）大西洋太平洋岛屿中心跨越大陆架的极端推进是否像Bart和安德森（1995年）推断的那样频繁？ Bart和安德森（1995年）推断，自中新世中期以来，APIC至少跨越大陆架30次。这一点很重要，因为它表明小型APIC的进步比EAIS和WAIS的进步更频繁一个数量级。其他人则质疑Bart和安德森（1995）对地震反射的冰川不整合解释，并认为APIC的进展要少得多（即，Larter等人，1997年）。 最近在南极半岛外大陆架上的钻探已经取样了一些但不是全部的冰川单元，但是沉积物恢复很差，因此，冰川历史的解释仍然是模糊的。南极半岛现有的高分辨率地震网格只包含一条外大陆架区域走向线。这不足以解决冰川不整合解释的争议和最近ODP结果的区域相关性。建议高分辨率地震数据该项目的第二个目标是：1）扩大PI的努力，将他正在进行的和拟议的实验整合到路易斯安那州立大学的研究生课程中; 2）与巴吞鲁日公立高中一起开发一个试点推广计划。路易斯安那州教育部采用了适用于所有科学的科学标准。这些标准反映了9至12年级的学生应该能够做什么和知道。PI将针对这些标准之一，即科学作为探究标准1基准。PI将奋进与学生分享进行科学研究的兴奋，以鼓励学生在大学阶段将地球科学作为一个研究领域。