Glacial History of the Amundsen Sea Shelf

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，支持对阿蒙森海地区进行海洋地质调查，以更好地了解南极西部冰盖（WAIS）的消冰历史。西海冰原可能天生就不稳定，因为它是世界上最后一个基于海洋的冰盖。与南极洲西部的其他海湾不同，从WAIS内部流入阿蒙森海的主要冰流缺乏支撑的冰架。这些冰流的远端部分（松岛冰川和思韦茨冰川）的质量平衡数据似乎处于平衡状态或可能变为负值。由于这两种冰流都有向冰盖中心向下倾斜的床，由于持续变薄或海平面上升而导致的基准线退缩可能引发不可逆转的基准线退缩，导致冰盖解体和随之而来的全球海平面上升。从阿蒙森海获得的有限的海洋地质和地球物理数据表明，直到最近的1000到2000年前，阿蒙森海内部的海湾可能一直被磨成的冰或冰架所占据，这些冰可能在历史上迅速消退。该项目是对西经100度至西经130度的阿蒙森海大陆架的海洋地质和地球物理学研究，旨在解决WAIS科学计划优先目标H2中的阿蒙森海部分：“东罗斯、别令斯豪森和阿蒙森海的消冰历史是什么？”该项目将检查阿蒙森海大陆架的水深数据，以确定以前冰蒸汽通道的位置，并帮助选择沉积物取样的地点。将进行单通道地震反射研究，以确定沉积物厚度模式，帮助选择取心地点，并定位和识别指示前地面冰的形态特征（例如，冰碛、冲刷、凹槽、条纹、楔形和三角洲等）。取芯将沿原冰流线集中。岩心样本将在实验室进行沉积学分析，以确定是否存在基碛物（表明以前的地面冰及其以前的范围），并分析钙质和硅质微化石。将利用加速器质谱法（AMS）测定酸不溶性颗粒有机碳的碳-14年代，确定在大陆架断裂附近假定的末次冰期最大值位置的接地线和冰架退缩的年代学。该项目将与一个物理海洋学项目共享阿蒙森海的船舶时间。收集的海洋地质数据和样本将与其他调查人员的发现相结合，以发展对西海地区历史的全面解释。

This award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, supports a marine geological investigation of the Amundsen Sea region toward a better understanding of the deglaciation history of the West Antarctic Ice Sheet (WAIS). The WAIS may be inherently unstable because it is the last marine-based ice sheet in the world. Unlike other embayments in West Antarctica, major ice streams draining into the Amundsen Sea from the interior of the WAIS lack buttressing ice shelves. Mass balance data for the distal portions of these ice streams (Pine Island and Thwaites glaciers) appear to be in balance or may be becoming negative. Because both ice streams have beds that slope downward toward the center of the ice sheet, grounding-line recession resulting from either continued thinning or sea-level rise could trigger irreversible grounding-line retreat, leading to ice-sheet disintegration and consequent global sea-level rise. The limited marine geological and geophysical data available from the Amundsen Sea suggest that grounded ice or an ice shelf occupied the inner Amundsen Sea embayment until perhaps as recently as 1000 to 2000 years ago, and this ice may have retreated rapidly in historic time.This project, a study of the marine geology and geophysics of the Amundsen Sea continental shelf from 100 degrees W to 130 degrees W, is designed to address the Amundsen Sea part of WAIS Science Plan Priority Goal H2: "What is the deglaciation history in the eastern Ross, the Bellingshausen and Amundsen Seas?" This project will examine bathymetric data of the Amundsen Sea continental shelf to determine the positions of former ice-steam channels, and to aid in choosing sites for sediment coring. Single-channel seismic reflection studies will be conducted in order to determine sediment-thickness patterns, to aid in choice of coring sites, and to locate and identify morphologic features indicative of former grounded ice (e.g., moraines, scours, flutes, striations, till wedges and deltas, etc.). Coring will be concentrated along former ice flow-lines. Core samples will be analyzed in the laboratory for sedimentology, to determine whether of not basal tills are present (indicating former grounded ice and its former extent), and for calcareous and siliceous microfossils. The chronology of grounding-line and ice-shelf retreat from a presumed Last Glacial Maximum position near the shelf break will be established using accelerator mass spectrometry (AMS) carbon-14 dates of acid-insoluble particulate organic carbon.This project will share ship time in the Amundsen Sea with a physical oceanographic project. Marine geologic data and samples collected will be integrated with findings of other investigators toward developing a comprehensive interpretation of the history of the WAIS.