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

本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委员会（UKRI/NERC）通过NSF/GEO-NERC牵头机构协议共同资助。该协议允许美国/英国提交一份联合提案，并由其调查员拥有最大比例预算的机构进行同行评审。在成功地共同确定一项奖励后，每个机构为预算的比例和与它自己的工作有关的调查人员提供资金。风化是一个重要的过程，它从地球表面的岩石和矿物质中释放出生命所必需的营养物质。该项目旨在了解格陵兰冰盖下大型冰川对风化过程的影响及其对生命的影响。在夏季，营养物质和其他产品随着冰融化的水被冲出格陵兰冰盖。虽然这些产品已在春季和夏季取样，但尚不清楚风化过程在冬季有何不同。在这个项目中，研究人员将对格陵兰岛的两个冰川出口——isunguata Sermia和Leverett冰川——在冰期前形成的季节性冰进行取样，以评估反映冰原下冬季条件的化学和微生物过程——这是新鲜融水输入最少的时期。这些样本将增加对格陵兰冰盖下冬季条件的了解，并有助于更好地了解大部分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、过去冰期条件下以及未来冰川消融世界中对地球营养循环的作用。格陵兰冰原是世界海洋重要生物元素的主要出口国。然而，我们对冰盖的化学和生物通量的大部分认识来自夏季出海口冰川的流出，这些冰川的水道化水只接触到冰川床的有限部分。大部分的冰川-河床界面包含缓慢流动的、分布的水，不代表这种通量。该项目将验证一个假设，即格陵兰冰盖出口下的越冬化学和生物过程与夏季流出有很大不同，并代表了一个了解广泛但通常难以接近的分布流动的窗口。主要的样品采集方法是早春取冰芯，冰芯是由冬季冰下流在冰川末端形成的。这一流动的化学、矿物学和生物成分将与融化季节初始、峰值和结束阶段出现的物质进行比较。在北极的其他地方，冰冻的越冬冰下物质的化学成分表明，即使与第一次春季融化相比，氧气或沉积物的供应也明显有限，这支持了冰层揭示了一个独特的越冬系统的观点。isunguata Sermia和Leverett冰川的融化冰和流出物将在两年内取样。西格陵兰岛的这些出水口所排放的集水区的大小相差不止一个数量级，因此测试了尺度对生物地球化学的影响。将通过探地雷达和冰井温度剖面来表征Naled冰结构。将评估水的地球化学、碳酸盐和硫酸盐的稳定同位素以及冰和水的悬浮沉积物的矿物学。这些分析将记录在冬季低流量条件和夏季融化高峰之间冰川床上矿物通量和大气气体供应的变化。还将测量微生物丰度、多样性、宏基因组学和生物量的稳定同位素，以了解地球化学条件与生物群落之间的伴随关系。研究人员将把研究结果纳入一系列拓展工作，包括为地球与环境科学中心开发新的课程模块，为代表性不足的学生提供研究机会，作为“通往研究的桥梁”项目的一部分，并为市场科学项目准备实践活动。该奖项反映了美国国家科学基金会的法定使命，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。

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.