Collaborative Research: Larsen Ice Shelf: A Model for Antarctic Ice Shelf-Ocean Dynamics

[107167 . prentice]该奖项由极地项目办公室的南极地质和地球物理项目提供，支持位于卡本代尔的南伊利诺伊大学和新罕布什尔大学之间的合作研究项目。对来自威德尔海陆架的现代沉积物和岩心样本的有孔虫和稳定同位素分析将用于解决南极拉森冰架最近崩塌的机制。位于威德尔海西北边缘、南极半岛东侧的拉森冰架可能正在崩塌，原因是年平均大气温度显著升高（~+2.5摄氏度），导致每年至少有4个月的时间处于无海冰状态。另外，由于相对温暖的深水侵入而导致的基底冰架融化可能是主要原因。2000年5月6日至6月1日，利用“纳撒尼尔·b·帕尔默”（NBP）科考船在威德尔海陆架原Larsen冰架a （lisa）覆盖的大片区域收集了一系列表层沉积物取样、水文模型、高分辨率地震数据和重力岩心。将分析从地表沉积物捕获物和重力岩心收集的样品，以获得有孔虫分布（浮游生物和底栖生物；活的和死的）数据，以及浮游生物和底栖有孔虫氧和碳同位素分析（d18O和d13C）。过去的研究表明，有孔虫分布与南极大陆架底水质量之间存在很强的相关性。从威德尔海西部主要水团中采集的水样将被测量其d18O和d13C组成。本文将对选定的底栖有孔虫建立d18O和d13C平衡降水的程度，并对它们的d18O和d13C值进行现代海洋学校准。现代有孔虫分布和地球化学数据将应用于卡斯滕岩心和巨型活塞岩心样本，除了其他合作研究外，还将重建与LIS-A最近崩溃相关的海洋和生物变化。以下假设将得到验证：相对温暖的威德尔深水侵入威德尔海西部大陆架导致了利斯- a的退缩。这些结果将有助于了解冰架崩塌的海洋因果机制，并提供北半球气候和海洋变化与南半球之间的联系。为了确定LIS和海底的自然变异性，将重建全新世大部分时间的底栖有孔虫分布以及浮游和底栖有孔虫d18O和d13C的详细记录。这项工作将有助于探测南极冰架崩塌的人为强迫。

0107167PrenticeThis award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, supports a collaborative research project between the University of Southern Illinois at Carbondale and the University of New Hampshire. Foraminiferal and stable isotopic analyses of modern sediments and core samples from the Weddell Sea shelf will be used to address the mechanisms underlying the recent collapse of the Larsen Ice Shelf, Antarctica. The Larsen Ice Shelf, located on the northwestern margin of the Weddell Sea along the east side of the Antarctic Peninsula, may be collapsing due to a marked increase in mean annual atmospheric temperature (~+2.5 degrees C) that has resulted in sea-ice free conditions for at least 4 months per year. Alternatively, basal ice shelf melting due to intrusion of relatively warm deepwater may be primarily responsible. From May 6 to June 1, 2000, the Research Vessel Nathaniel B. Palmer (NBP) was used to collect a series of surface sediment grab samples, hydrographic casts, high-resolution seismic data, and gravity cores from a large region of the Weddell Sea shelf formerly covered by the Larsen Ice Shelf-A (LIS-A).Samples collected from surface sediment grabs and gravity cores will be analyzed for foraminiferal distribution (planktonic and benthic; living and dead) data as well as planktonic and benthic foraminiferal oxygen and carbon isotopic analyses (d18O and d13C). Past work has shown a strong correlation between foraminiferal distributions and bottom water masses on the Antarctic continental shelf. Water samples collected from the major water masses in the western Weddell Sea will be measured for their d18O and d13C compositions. The extent of equilibrium d18O and d13C precipitation will be established for selected benthic foraminifers, as well as their d18O and d13C values calibrated to the modern oceanography.The modern foraminiferal distribution and geochemical data will be applied to kasten core and jumbo piston core samples, in addition to other collaborative research, to reconstruct the oceanographic and biotic changes associated with the recent collapse of the LIS-A. The following hypothesis will be tested: That incursions of relatively warm Weddell Deep Water onto the western Weddell Sea shelf has led to the retreat of the LIS-A. The results will contribute to understanding oceanic causal mechanisms for ice shelf collapse and provide a link between Northern Hemisphere climatic and oceanographic change and the Southern Hemisphere. A detailed record of benthic foraminiferal distribution and also planktonic and benthic foraminiferal d18O and d13C will be reconstructed for much of the Holocene in order to determine the natural variability of the LIS and underlying ocean. This work will contribute to detection of anthropogenic forcing of Antarctic ice shelf collapse.