NSFGEO-NERC:Collaborative Research: Chemistry and Biology under Low Flow Hydrologic Conditions Beneath the Greenland Ice Sheet Revealed through Naturally Emerging Subglacial Water

该项目由美国国家科学基金会地球科学理事会 (NSF/GEO) 和英国国家环境研究理事会 (UKRI/NERC) 通过 NSF/GEO-NERC 牵头机构协议共同资助。该协议允许美国/英国的单一联合提案由其调查员拥有最大预算比例的机构提交并进行同行评审。在成功联合确定奖项后，每个机构都会资助与其各自工作部分相关的预算比例和研究人员。风化是一个重要的过程，它从地球表面的岩石和矿物中释放出生命所必需的营养物质。该项目旨在了解大型冰川对格陵兰冰盖下风化过程的影响以及对生命的影响。在夏季，营养物质和其他产物被融化的冰水从格陵兰冰盖冲走。虽然这些产品在春季和夏季进行了采样，但尚不清楚冬季的风化过程有何不同。在这个项目中，研究人员将对格陵兰岛两个冰川出口（伊桑瓜塔塞尔米亚冰川和莱弗里特冰川）前形成的季节性冰进行采样，以评估反映冰盖下冬季条件的化学和微生物过程，即新鲜融水输入最少的时期。这些样本将增加人们对格陵兰冰盖下冬季状况的了解，并有助于更好地了解基本上无法进入的冰盖内部部分。这些信息将有助于评估过去的情况，当时较冷的大气条件导致通过冰盖和冰川床的融水输入最少。这些分析将有助于了解冰川在当前、过去的冰河时代条件下以及未来冰川消退的世界中对地球营养循环的作用。格陵兰冰盖是向世界海洋输出重要生物元素的主要来源。然而，我们对冰盖化学和生物通量的大部分了解来自于夏季流出冰川的流出，其渠道化的水仅接触冰川床的有限部分。大部分冰川床界面包含缓慢流动的分布水，不能代表这种通量。该项目将检验这样一个假设：格陵兰冰盖出口处的冬季化学和生物过程与夏季流出物有很大不同，并且代表了了解广泛但通常难以到达的分布式流动的窗口。主要的样本采集方法是早春对冬季冰下流在冰川末端形成的冰进行取芯。该流的化学、矿物学和生物成分将与融化季节的初始、高峰和末期出现的物质进行比较。在北极的其他地方，与春季第一次融化相比，冬季冰冻的冰下物质的化学成分显示出氧气或沉积物供应的显着限制，这支持了冰层揭示了独特的越冬系统的观点。伊桑瓜塔塞尔米亚冰川和莱弗里特冰川的冰和流出物将在两年内进行采样。西格陵兰岛的这些排水口在其排水的集水区大小方面相差超过一个数量级，从而测试了规模对生物地球化学的影响。 Naled冰结构将通过探地雷达和冰钻孔温度剖面来表征。将评估水体地球化学、碳酸盐和硫酸盐的稳定同位素以及冰和水悬浮沉积物的矿物学。这些分析将记录冬季低流量条件和夏季融化高峰之间冰川床上矿物质通量和大气气体供应的变化。微生物丰度、多样性、宏基因组学和生物量的稳定同位素也将被测量，以了解地球化学条件和生物群落之间的伴随关系。研究人员将把研究成果纳入一系列推广工作中，包括为地球与环境科学中心开发一个新的课程模块，作为研究桥梁计划的一部分为代表性不足的学生提供研究机会，以及为市场科学计划准备实践活动。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project is jointly funded by the National Science Foundation’s Directorate of Geosciences (NSF/GEO) and the National Environment Research Council (UKRI/NERC) of the United Kingdom (UK) via the NSF/GEO-NERC Lead Agency Agreement. This Agreement allows a single joint US/UK proposal to be submitted and peer-reviewed by the Agency whose investigator has the largest proportion of the budget. Upon successful joint determination of an award, each Agency funds the proportion of the budget and the investigators associated with its own component of the work.Weathering is an important process that releases nutrients that are essential for life from rocks and minerals in the Earth’s surface. This project seeks to understand the effect of large glaciers on weathering processes beneath the Greenland Ice Sheet and the consequences for life. During summer, nutrients and other products are flushed out of the Greenland Ice Sheet with water from melting ice. While these products have been sampled in spring and summer, it is not known how weathering processes are different during winter. In this project, researchers will sample the seasonal ice that forms in front of two of Greenland’s glacial outlets, Isunnguata Sermia and Leverett Glacier, during the freezing months to assess the chemistry and microbiology processes that reflect wintertime conditions beneath the ice sheet – periods when input of fresh meltwater is minimal. These samples will increase knowledge of winter conditions under the Greenland Ice Sheet and help better understand the interior portions of the ice sheet which are largely inaccessible. Such information will help in assessing past conditions, when colder atmospheric conditions resulted in minimal meltwater input through the ice sheet and to the glacial bed. These analyses will inform understanding of the role of glaciers on earth’s nutrient cycles presently, under past ice age conditions, and in a future deglaciating world.The Greenland Ice Sheet is a major exporter of biologically important elements to the world’s oceans. However, most of our knowledge of chemical and biological fluxes from the ice sheet comes from the summer outflux of outlet glaciers whose channelized waters contact only a limited portion of the glacier bed. The majority of the glacier-bed interface contains slow-flowing, distributed waters not representative of this flux. The project will test the hypothesis that overwinter chemical and biological processes under outlets of the Greenland Ice Sheet differ substantially from summer outflow and represent a window into widespread, but typically inaccessible, distributed flow. The principal sample collection method will be early spring coring of naled ice that forms at glacial termini from wintertime subglacial flow. Chemical, mineralogical, and biological constituents of this flow will be compared to material emerging from the initial, peak, and terminal phases of the melt season. Elsewhere in the Arctic, the chemistry of frozen overwinter subglacial material shows significant limitation in oxygen or sediment supply compared with even the first spring melt, supporting the idea that naled ice reveals a unique overwinter system. The naled ice and outflow of Isunnguata Sermia and Leverett Glacier will be sampled over two years. These West Greenland outlets differ by more than an order of magnitude in the size of the catchments they drain, thereby testing the effect of scale on biogeochemistry. Naled ice structure will be characterized by ground penetrating radar and ice borehole temperature profiles. The aqueous geochemistry, stable isotopes of carbonate and sulphate, and mineralogy of the suspended sediment of ice and water will be assessed. These analyses will document changes in the mineral flux and supply of atmospheric gases at the glacial bed between winter low flow conditions and peak summer melt. Microbial abundance, diversity, metagenomics, and stable isotopes of biomass will also be measured to understand the concomitant relationship between geochemical conditions and biological communities. Researchers will incorporate findings into a number of outreach efforts including developing a new curriculum module for the Center for Earth and Environmental Sciences, providing research opportunities for underrepresented students as part of the Bridge to Research Program and preparing hands-on activities for the Market Science Program.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.