PECASE: Relative frequency and phase of extreme expansions of the Antarctic Ice Sheets during the late Neogene
PROPOSAL NO.: 0094078
PRINCIPAL INVESTIGATOR: Bart, Philip
INSTITUTION NAME: Louisiana State University & Agricultural and Mechanical College
TITLE: CAREER: Relative frequency and phase of extreme expansions of the Antarctic Ice Sheets during the late Neogene
NSF RECEIVED DATE: 07/27/2000
Expansions 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.
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