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

该奖项由极地计划办公室南极地质和地球物理计划提供，支持南伊利诺伊大学卡本代尔分校和新汉普郡大学之间的合作研究项目。将对威德尔海陆架的现代沉积物和岩心样品进行有孔虫和稳定同位素分析，以探讨南极洲拉森冰架最近坍塌的机制。位于南极半岛东侧韦德尔海西北部边缘的拉森冰架可能正在坍塌，原因是年平均气温显著上升(~2.5摄氏度)，导致每年至少有4个月没有海冰。另一种可能是，相对温暖的深海入侵导致的底部冰架融化可能是主要原因。从2000年5月6日至6月1日，纳撒尼尔·B·帕尔默(NBP)考察船从以前被拉森冰架(LIS-A)覆盖的韦德尔海陆架的大片区域收集了一系列表层沉积物抓取样本、水文预报、高分辨率地震数据和重力岩心。从表层沉积物抓取和重力岩心收集的样本将被分析有孔虫分布(浮游和底栖动物；活的和死的)以及浮游和底栖有孔虫的氧和碳同位素分析(d18O和d13C)。过去的研究表明，南极大陆架上有孔虫的分布与底层水团之间存在很强的相关性。从威德尔海西部主要水团采集的水样将被测量其d18O和d13C组成。将为选定的海底有孔虫建立平衡的d18O和d13C降水范围，以及根据现代海洋学校准它们的d18O和d13C值。现代有孔虫分布和地球化学数据将应用于Kasten岩芯和巨型活塞岩心样品，以及其他合作研究，以重建与最近LIS-A坍塌相关的海洋学和生物变化。将检验以下假设：相对温暖的韦德尔深水侵入西部韦德尔海陆架，导致了LIS-A的撤退。这一结果将有助于理解冰架崩塌的海洋成因机制，并提供北半球气候和海洋变化与南半球之间的联系。将重建全新世大部分地区底栖有孔虫分布的详细记录，以及浮游和底栖有孔虫d18O和d13C，以确定LIS和下伏海洋的自然变异性。这项工作将有助于探测南极冰架坍塌的人为强迫。

0003633IshmanAbstractThis 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.