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

建议没有。[0094078]主要研究者：Bart， philip机构名称：路易斯安那州立大学农业与机械学院标题：职业：新千年晚期南极冰盖极端扩张的相对频率和阶段[f] [c]项目摘要：南极冰盖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，南极冰冻圈不是一个单一的实体，而是由三个主要元素组成：1)南极东部冰盖（EAIS）；2)南极西部冰盖（WAIS）；3)南极半岛冰帽（APIC）。区别特征包括：1)冰体积；2)基底高程；3)冰面高程；4)相对于纬度的位置。各种证据表明，国际货币基金组织在过去经历了重大波动，未来也将继续出现波动。波动的确切性质一直是许多激烈辩论的主题。根据一种推理，陆基东亚地震带自中新世中期形成以来一直相对稳定，只经历过较小的波动，而海基东亚地震带自中新世晚期以来一直是动态的，频繁起起落落。根据另一种假设，冰盖是同步前进和后退的。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。海平面高度的波动涉及许多方面（变化的频率、冰量变化的总体幅度等），这里提出的活动具体涉及冰盖向大陆架极端推进的频率和阶段。该项目将建立在以前对大陆架的地震地层调查的基础上。这些研究澄清了关于个别冰盖极端扩张的最小频率的许多问题，但仍存在一些重要问题。在项目过程中，将评估以下问题。问题1)EAIS和WAIS跨越大陆架的极端进展是否具有相似的频率和时间？这种评价是可能的，因为西部罗斯海大陆架（北部盆地）接受EAIS的排水，而东部罗斯海（东部盆地）接受WAIS的排水。Alonso et al.（1992）和Bart et al.（2000）分别对这两个领域的极端进步进行了定量分析。然而，现有的单通道地震网格不完整，不能用于确定盆地北部到东部的地层对比。为了解决这一问题，建议采集高分辨率地震资料（~2000公里）。问题2)APIC跨越大陆架的极端进展是否像Bart和Anderson（1995）推断的那样频繁？Bart和Anderson（1995）推断中新世中期以来APIC至少30次跨越大陆架。这一点很重要，因为它表明小型APIC的进步比EAIS和WAIS的进步要频繁一个数量级。其他人则对Bart和Anderson（1995）对地震反射的冰川不整合解释提出异议，并认为APIC的进展要少得多（例如，Larter等人，1997）。近年来对南极半岛外大陆架的钻探已取样了部分但不是全部的冰川单元，但沉积物恢复较差，因此，冰川历史的解释仍然不明确。南极半岛现有的高分辨率地震格网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和最近ODP结果的区域相关性的争议。建议在即将到来的（2002年1月）南极半岛巡航中获取高分辨率地震数据（~1000公里）来解决这些问题。该项目的第二个目标是：1)扩大PI的努力，将他正在进行的和提议的实验整合到路易斯安那州立大学的研究生课程中；2)与巴吞鲁日的一所公立高中开展试点推广计划。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年级到12年级的学生应该能够做什么和知道什么。PI将以其中一个标准为目标，即科学探究标准1基准。地球科学计划将努力与学生分享进行科学研究的乐趣，以鼓励学生在大学阶段学习地球科学。

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.