Timing and Duration of the LGM and Post-LGM Grounding Events in Whales Deep Paleo Ice Stream, Eastern Ross Sea Middle Continental Shelf

知识价值：来自东罗斯海大陆架的证据表明，在最后一次冰期循环中，南极西部冰盖前进和后退，但尚不清楚冰盖是前进到大陆架边缘还是仅仅到大陆架中部。对于南极西部冰盖振荡的原因、方式和时间，这两种末端情景提供了不同的解释。该项目建议获取来自鲸鱼深的地震、多波束和岩心数据，以评估两次地面冰向鲸鱼深盆地（罗斯海东部的南极西部冰盖古冰流槽）的外大陆架和中大陆架推进的时间和持续时间。接地事件由地震可分辨的接地带楔块表示。PI将收集来自接地带直径的原位底栖有孔虫的放射性碳年代，以及来自覆盖在接地带直径上的开放海洋泥浆的酸不溶性有机物的斜坡热解放射性碳年代。使用这些数据，PI将计算两个接地事件的持续时间。此外，该项目还将检验一个数值模型的预测，即南极西部冰盖的退缩必然涉及冰盖海洋末端的融化。将从活塞岩心中提取接地区直径的孔隙水，以确定盐度和&amp；#948；18O值应该表明在接地线上是否发生了明显的熔化。更广泛的影响：收集到的数据将提供末次冰期极大期前进和后退的时间和模式的限制条件，这些限制条件可被纳入冰面高程变化的解释中。拟议的活动将为本科生/研究生和路易斯安那州高中科学教师提供宝贵的实地和研究培训。这项研究将与初中和高中理科学生以及路易斯安那州立大学自然科学博物馆周末科学项目的参观者进行互动分享。

Intellectual Merit: Evidence from the eastern Ross Sea continental shelf indicates that the West Antarctic Ice Sheet advanced and retreated during the last glacial cycle, but it is unclear whether the ice sheet advanced to the shelf edge or just to the middle shelf. These two end-member scenarios offer different interpretations as to why, how, and when the West Antarctic Ice Sheet oscillated. The PI proposes to acquire seismic, multibeam, and core data from Whales Deep, to evaluate the timing and duration of two advances of grounded ice to the outer and middle shelf of the Whales Deep Basin, a West Antarctic Ice Sheet paleo ice stream trough in eastern Ross Sea. Grounding events are represented by seismically resolvable Grounding Zone Wedges. The PI will collect radiocarbon dates on in situ benthic foraminifera from the grounding zone diamict as well as ramped pyrolysis radiocarbon dates on acid insoluble organics from open-marine mud overlying the grounding zone diamict. Using these data the PI will calculate the duration of the two grounding events. Furthermore, the PI will test a numerical model prediction that West Antarctic Ice Sheet retreat must have involved melting at the marine terminus of the ice sheet. Pore-water from the grounding zone diamict will be extracted from piston cores to determine salinity and δ18O values that should indicate if significant melting occurred at the grounding line.Broader impacts: The data collected will provide constraints on the timing and pattern of Last Glacial Maximum advance and retreat that can be incorporated into interpretations of ice-surface elevation changes. The proposed activities will provide valuable field and research training to undergraduate/graduate students and a Louisiana high-school science teacher. The research will be interactively shared with middle- and high-school science students and with visitors to the LSU Museum of Natural Science Weekend-Science Program.