Doctoral Dissertation Research: The impact of permafrost thaw on the fate and magnitude of carbon aquatic transport from Arctic tundra soil

北极流域的永久冻土解冻触发了先前被隔离的古老碳向大气和河流系统的释放——这是一种加速气候变暖的反馈。几十年来，大气中碳的释放已经得到了充分的记录；然而，水更难监测，而且它在北极碳循环中的作用经常被忽视。本研究将探讨北极地下水和水源流在长期冻土碳释放中的环境驱动因素。更好地理解水在变暖的北极碳循环中所扮演的新角色，将有助于改善区域碳预算，量化永久冻土下的流域中通过河流输出的土地碳损失量。这项研究还将有助于监测气候变化和由此导致的永久冻土融化对古代永久冻土碳释放的影响，方法是对河流中携带的溶解碳进行碳定年，以确定古代永久冻土的特征。在阿拉斯加内陆的一个长期实验研究地点，每年从土壤中流失的50%的土壤碳在大气碳通量测量中没有计算在内。据推测，丢失的50%的碳以溶解的有机碳通量的形式输出，并且随着永久冻土融化的增加，每年释放的古代永久冻土碳的数量也在增加。本研究将：(1)有助于解决北极生态系统净碳收支问题，并有助于参数化未来的地球系统模型；(2)利用放射性碳测年技术确定古冻土中溶解有机碳的比例；(3)确定解冻等环境驱动因素如何影响溶解有机碳浓度和年龄，以帮助约束未来溶解有机碳出口的预测。此外，项目团队将在亚利桑那州和阿拉斯加内陆的实地周围的当地社区内促进各种外展活动，包括更广泛的公众以及未来的年轻科学家群体参与这项工作。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。

Permafrost thaw in Arctic watersheds triggers the release of previously sequestered, ancient carbon to the atmosphere and to stream systems - a feedback that accelerates climate warming. Atmospheric release of carbon has been well-documented for decades; however, water is more difficult to monitor and its role in the Arctic carbon cycle has often been overlooked. This research will explore the environmental drivers that Arctic groundwater and headwater streams play in long-term permafrost carbon release. Better understanding the emerging role that water plays in the carbon cycle in a warming Arctic will help improve regional carbon budgets, quantifying the amount of carbon lost from the land that is exported via rivers in a watershed underlain by permafrost. The research will also aid in monitoring the impacts that climate change and resulting permafrost thaw have on ancient permafrost carbon release by carbon dating the dissolved carbon carried away in rivers to identify ancient permafrost signatures. At a long-term experimental study site in interior Alaska, 50% of the soil carbon lost from soils annually was unaccounted for in atmospheric carbon flux measurements. The missing 50% of carbon lost is hypothesized to be exported in dissolved organic carbon fluxes and that an increasing amount of ancient, permafrost carbon is released each year with increasing permafrost thaw. This research will (1) help to resolve the Arctic net ecosystem carbon budget and help to parameterize future Earth System Models; (2) identify the proportion of dissolved organic carbon that is ancient permafrost carbon, using radiocarbon dating; and (3) identify how environmental drivers, such as thaw, impact dissolved organic carbon concentration and age in order to help constrain future predictions of dissolved organic carbon export. Further, the project team will facilitate various outreach activities in Arizona and within the local community surrounding the field site in interior Alaska, to include the broader public as well as a future cohort of young scientists in this work.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.