Submarine Basins, Steppe, and Sea Ice: Paleoclimate and Paleoecology of the Late Pleistocene and Holocene Bering Sea Shelf

海底盆地、草原和海冰：晚更新世和全新世白令海陆架的古气候和古生态

• 批准号: 2117052
• 负责人: Sarah Fowell
• 金额: $ 172.16万
• 依托单位: University of Alaska Fairbanks Campus
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-08-15 至 2025-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2117052&HistoricalAwards=false
• 关键词: Submarine; Basins; Steppe; Sea; Ice

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2)The Bering Land Bridge served as a migration corridor for plants, animals, and humans passing between Eurasia and North America during glacial stages of the Quaternary period (the last ~2.6 million years). During interglacial stages, rising sea level floods this land bridge, creating a marine gateway that connects the Pacific and Arctic oceans and modulates the global climate system. Although the Bering Sea shelf is the only place on Earth where fluctuations in Quaternary sea level repeatedly opened and closed such a gateway, sediment cores for the purpose of paleoenvironmental reconstruction have never been collected from the central and southern portions of the submerged land bridge. To determine how the most recent glacial/interglacial transition affected the ecology and climate of the Bering Land Bridge, the project team will collect, analyze, and archive terrestrial and marine sediment preserved in sedimentary basins across the Bering Sea shelf. Because these basins occupied topographic depressions on the Bering Land Bridge, they were likely to have been sites of freshwater lakes and terrestrial sediment deposition during glacial stages. Researchers will use a suite of traditional and cutting-edge paleoclimate proxies, including pollen, diatoms, and stable isotopes, to reconstruct the vegetation of interior and coastal sites on the Bering Land Bridge and evaluate the relationship between sea ice extent and aridity during and after the last glacial stage. Results will address longstanding questions regarding migration patterns of plants and animals, resources available to human populations, and the role of the marine gateway during the most recent past episode of global warming. Cores of Late Pleistocene and Holocene sediment will be collected from transects of five submarine basins located between the Bering Strait and the southern shelf edge: Norton Basin (64 N), St. Matthew Basin (62.5 N), Navarin Basin (62 N), St. George Basin (55.5 N), and the North Aleutian Basin (56 N). Existing US Geological Survey and industry seismic data suggest significant accumulation of Holocene and Pleistocene sediment fill in these basins. To maximize sediment recovery, the team will deploy a variety of coring apparatus, including a multicore system, a vibracorer, and gravity corers. New Chirp sub bottom data will be used to provide high-resolution imaging of the basin fill and subsurface topography in order to refine selection of both sites and apparatus. Pollen analysis of the Pleistocene section will permit reconstruction of the vegetation of the central and southern Bering Land Bridge and test the hypothesis that relatively humid conditions in low elevation, coastal regions provided a refugium for woody plants. Identification and dating of the transition between terrestrial and marine sediment will serve to constrain the rate and timing of Holocene sea-level rise. Micropaleontological and geochemical analyses of marine sediment will permit reconstruction of sea ice extent, primary productivity, and organic matter source. Comparison of marine records from sites near the shelf edge with coeval terrestrial records from the inner shelf will allow identification of terrestrial-marine linkages. These data will be used to test the hypothesis that when sea ice retreats during deglaciation, primary productivity on the Bering Shelf increases in sync with humidity on the Beringian continent. Results of this project will further our understanding of ocean circulation, the effect of sea ice on global climate, and the paleoecology of the migration corridor. The Beringian Standstill hypothesis suggests that ancestors of all Native Americans were isolated from Eurasian populations for thousands of years prior to migrating to North America. Fossil pollen records from terrestrial sites on the Bering Land Bridge are thus crucial to assessing the resources available to Late Pleistocene inhabitants of Beringia. Because the results of this project are likely to be of interest to Alaska Natives, the project team will collaborate with the Shared Beringian Heritage Program, the Bering Land Bridge National Preserve, and the Alaska Regional Office of the National Park Service. A PolarTREC teacher will design activities and lesson plans to promote understanding of land bridge paleoecology, and the Alaska Teen Media Institute will create video, web, and social media products during the science cruise. Curricula will be delivered in Alaskan schools, and results will be disseminated to stakeholders via public presentations and a traveling museum exhibit. This project will also provide training for multiple undergraduate and graduate students at sea, in university laboratories, and at international conferences.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

该奖项全部或部分由2021年美国救援计划法案（公法117-2）资助，白令陆桥在第四纪（最后约260万年）的冰川阶段作为植物，动物和人类在欧亚大陆和北美之间的迁移走廊。在间冰期阶段，海平面上升淹没了这座陆桥，形成了一个连接太平洋和北冰洋的海洋门户，并调节了全球气候系统。虽然白令海大陆架是地球上唯一一个第四纪海平面波动反复打开和关闭这样一个门户的地方，但从未从淹没的陆桥中部和南部收集过用于古环境重建的沉积物岩心。为了确定最近的冰川/间冰期过渡如何影响白令海陆桥的生态和气候，项目团队将收集、分析和存档白令海大陆架沉积盆地中保存的陆地和海洋沉积物。由于这些盆地占据了白令陆桥上的地形洼地，它们很可能是冰川期淡水湖和陆地沉积物沉积的场所。研究人员将使用一套传统和尖端的古气候代理，包括花粉，硅藻和稳定同位素，以重建白令陆桥上的内部和沿海地区的植被，并评估海冰范围与末次冰期期间和之后的干旱之间的关系。研究结果将解决长期存在的问题，包括植物和动物的迁移模式、人类可用的资源以及海洋门户在最近一次全球变暖中的作用。晚更新世和全新世沉积物的岩芯将从位于白令海峡和南部大陆架边缘之间的五个海底盆地的剖面中收集：诺顿盆地（北纬64度）、圣马修盆地（北纬62.5度）、纳瓦林盆地（北纬62度）、圣乔治盆地（北纬55.5度）和北阿留申盆地（北纬56度）。     现有的美国地质调查局和工业地震数据表明，这些盆地中全新世和更新世沉积物堆积显著。为了最大限度地回收沉积物，该小组将部署各种取芯仪器，包括多芯系统、振动器和重力取芯器。 新的Chirp海底下数据将用于提供盆地填充和地下地形的高分辨率成像，以改进场地和设备的选择。更新世部分的花粉分析将允许重建白令陆桥中部和南部的植被，并测试假设，即在低海拔，沿海地区相对潮湿的条件下提供了木本植物的避难所。陆地和海洋沉积物之间的过渡的识别和定年将有助于限制全新世海平面上升的速度和时间。海洋沉积物的微体古生物学和地球化学分析将允许重建海冰范围，初级生产力和有机质来源。将大陆架边缘附近的海洋记录与大陆架内部同时期的陆地记录进行比较，将有助于确定陆地-海洋的联系。这些数据将被用来检验一个假设，即当海冰在冰消期退缩时，白令大陆架的初级生产力与白令大陆的湿度同步增加。该项目的结果将进一步加深我们对海洋环流、海冰对全球气候的影响以及移民走廊的古生态学的理解。白令人停滞假说认为，所有美洲原住民的祖先在迁移到北美之前与欧亚人口隔离了数千年。因此，白令陆桥上陆地站点的化石花粉记录对于评估白令半岛晚更新世居民可用的资源至关重要。由于该项目的结果可能会引起阿拉斯加原住民的兴趣，项目小组将与共享白令遗产计划、白令陆桥国家保护区和国家公园服务的阿拉斯加地区办事处合作。一名PolartREC教师将设计活动和课程计划，以促进对陆桥古生态学的理解，阿拉斯加青少年媒体研究所将在科学巡航期间制作视频、网络和社交媒体产品。课程将在阿拉斯加的学校提供，结果将通过公开演讲和巡回博物馆展览传播给利益相关者。该项目还将在海上、大学实验室和国际会议上为多名本科生和研究生提供培训。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。