Collaborative Research: Sea-level rise, coastal wetland expansion, and proglacial lake contributions to abrupt increases in northern atmospheric CH4 during the last deglaciation

这项多学科研究旨在了解北方半球新淹没的陆地地区在最后一次冰消期（18-8 ka）的大气甲烷浓度迅速增加的时间，规模和整体贡献。极地冰芯记录显示，在此期间，大气中甲烷浓度动态增加，但甲烷的来源仍然是许多争论的主题。这项研究将测量甲烷排放量的同位素值从现场样品提供特定区域的估计甲烷排放量从沿海湿地，泥炭地，冰前湖，和其他湖泊类型（如热喀斯特和冰后期湖泊），因为最后一次冰消期与冰芯记录进行比较。这项研究将重建过去的甲烷排放量淹没冰消陆地地区（可能代表未知的北方来源增加大气中的甲烷浓度在这些时期），并评估他们的作用，在极地冰芯记录中观察到的甲烷突然增加。了解过去因海平面上升、湿地扩张、永久冻土融化和相关湖泊形成而被淹没的新淹没土地地区的甲烷排放量，将有助于更好地了解该地区可能加速的全球气候反馈。这一知识对于回答有关北方系统在全球环境变化中的作用以及我们理解海平面上升和沿海洪水的级联效应的能力等更大的社会问题至关重要。本研究使用了（a）北方大陆架地区和沿海湿地被快速冰消期海平面上升（SLR）淹没和（B）被冰川和冰淹没的冰前湖泊地区的全面古生态记录，片熔体，以记录其过去的贡献，在大气中的甲烷浓度突然增加。研究目标是：（1）综合新的和现有的大陆架，沿海湿地，区域SLR曲线，并proglacial-lake启动数据，重建新的淹没区极地30？N;（2）通过将新的和现有的甲烷通量整合到经验模型中，估计淹没的北方沿海地区过去从甲烷消耗森林和草原地区演变为较高排放的泥滩、沼泽和淡水湿地时的甲烷通量;（3）分析不同规模的冰前湖泊的新的和现有的甲烷通量，（4）利用稳定同位素（∂ 13 C，∂ D）甲烷和14 C测年，以限制这些新淹没的陆地地区甲烷通量的大小和时间;（5）将我们对淹没的大陆架、沿海湿地和冰前湖过去甲烷排放和同位素通量的重建与基于最近更高分辨率甲烷同位素数据的全球大气甲烷限制进行比较（∂ 13 C，∂该奖项反映了NSF的法定使命，并被认为是值得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的支持。

This multidisciplinary research seeks to understand the timing, magnitude, and overall contribution of newly flooded land areas in the northern hemisphere to rapid increases in atmospheric methane concentrations during the last deglaciation (18-8 ka). Polar ice core records reveal dynamic increases in atmospheric methane concentrations during this period, but the source of this methane remains the subject of much debate. This study will measure the isotopic values of methane emissions from field samples to provide region-specific estimates of methane emissions from coastal wetlands, peatlands, proglacial lakes, and other lake types (e.g. thermokarst and post-glacial lakes) since the last deglaciation for comparisons with ice core records. This research will reconstruct the past methane emissions from flooded deglacial land areas (potentially representing unknown northern sources of increased atmospheric methane concentrations during these periods) and assess their role in contributing to the abrupt methane increases observed in in polar ice core records. Knowledge of past methane emissions from newly inundated land areas flooded by sea level rise, wetland expansion, permafrost thaw, and associated lake formation will provide an improved understanding of global climate feedbacks that will likely accelerate in the region. This knowledge is critical to answering larger societal questions about the role of northern systems in global environmental change and our ability to understand the cascade of effects from sea level rise and coastal flooding.This research uses comprehensive paleoecological records of (a) northern continental shelf areas and coastal wetlands inundated by rapid deglacial sea-level rise (SLR) and (b) proglacial lake areas inundated by glacier and ice-sheet melt to document their past contributions to abrupt increases in atmospheric methane concentrations. The research goals are to: (1) synthesize new and existing shelf, coastal wetland, regional SLR curves, and proglacial-lake initiation data to reconstruct newly inundated areas poleward of 30? N; (2) estimate past methane flux from inundated northern coastal regions as they evolved from methane-consuming forest and grassland areas to higher emitting mudflats, marshes, and freshwater wetlands by integrating new and existing methane fluxes into an empirical model; (3) analyze new and existing methane fluxes from proglacial lakes of different sizes, ages and geographies to build an empirical model for reconstructing proglacial lake emissions from 18 ka to present (with an emphasis on the deglacial period,18-8 ka); (4) use stable isotopes (∂13C, ∂D) of methane and 14C dating to constrain the magnitude and timing of methane flux from these newly flooded land areas; and (5) compare our reconstructions of past methane emissions and isotope fluxes from inundated shelves, coastal wetlands, and proglacial lakes with global atmospheric methane constraints based on recent, higher resolution data of methane isotopes (∂13C, ∂D, 14C) from Greenland and Antarctic ice cores using atmospheric box modeling.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.