Collaborative Research: Is the export of ancient, labile carbon from glacial ecosystems driven by the deposition of fossil fuel combustion byproducts?

冰川和冰盖是第二大水库，占地球面积的10%。它们也构成了一个重要但鲜为人知的生态系统。加强冰川生物地球化学知识尤为重要，因为它们是对气候变暖最敏感的环境之一。最值得注意的是，由于气温上升、降水模式改变以及黑碳的沉积，冰川正在加速融化，这会使冰川表面变暗，增强其对光和热的吸收。冰川生态系统最近被确定为下游水生生态系统中古老但高度生物可用的溶解有机碳的重要来源。这一发现与年龄-反应性关系的逻辑观念背道而驰，在这种关系中，最不活跃的物质经受降解的时间最长，因此也是最古老的。自冰川泛滥以来，古代泥炭地和森林的残留物被认为是这种古老的、不稳定的有机碳的来源。作为本研究基础的初步结果挑战了泥炭地/森林来源假说，相反，表明冰川有机碳主要来自气溶胶沉积，并以未老化的形式进入冰川。这项研究将确定化石燃料衍生的气溶胶对冰川有机碳库的贡献，验证这种有机碳是否确实是古老和不稳定的，并量化其被输出到下游生态系统的程度。今天，大约60%的有机气溶胶来自人类活动，表明自工业革命以来有机沉积也大幅增加。因此，如果在阿拉斯加湾冰川上、冰川内和从冰川出口的有机物来自气溶胶，那么我们今天观察到的冰川生态系统结构是由数千英里外工业活动的废物提供的。如果是这种情况，那么出口到冰川下游生态系统的有机碳也将是人为来源，这表明这些接收生态系统相对于其工业化前的状态也发生了变化。由于燃烧产物的沉积是一种全球现象，所有生态系统可能都在接受这种古老的、不稳定的碳补贴。在较温暖的生态系统中，不稳定的碳意外之财可能会被迅速处理，其信号会丢失。在寒冷的冰川环境中，这些输入突出，使冰川成为探测和研究人为沉积的哨兵生态系统。尽管这项研究的重点是阿拉斯加湾的冰川，但研究结果将与任何接受沉积输入的生态系统相关。该项目提供了一个高度跨学科和协作的研究环境，来自科学领域代表性不足群体的本科生、硕士研究生和博士后研究员都将从中受益。合作的范围超出了资助的美国科学家，包括马克斯·普朗克研究所海洋地球化学组支持的德国同事。这一国际组成部分扩大了知识转移的可能性，并为美国的研究人员提供了获得独特的、最先进的分析设施的途径。研究结果将通过位于朱诺的美国林业局门登霍尔冰川游客中心向公众公布，为公众宣传气候变化对冰川的影响提供了机会。

Glaciers and ice sheets represent the second largest reservoir of water and cover 10% of the earth. They also constitute an important, but poorly understood ecosystem. Improving knowledge of glacier biogeochemistry is particularly important as they are among the environments most sensitive to climate warming. Most notably, glacier melting is accelerating due to rising temperatures, changing precipitation patterns and the deposition of black carbon, which darkens glacier surfaces enhancing their absorption of light and heat. Glacier ecosystems were recently identified as a significant source of ancient, yet highly bioavailable dissolved organic carbon to downstream aquatic ecosystems. This finding runs counter to logical perceptions of age-reactivity relationships, in which the least reactive material withstands degradation the longest and is therefore the oldest. The remnants of ancient peatlands and forests since overrun by glaciers have been invoked as a source of this ancient, labile organic carbon. Preliminary results upon which this study is based, challenge the peatland/forest source hypothesis, indicating instead that glacier organic carbon is predominantly from aerosol deposition and enters glaciers in a pre-aged form. This study will determine the contribution to the glacial organic carbon pool made by fossil fuel derived aerosols, verify whether this organic carbon is indeed ancient and labile, and quantify the extent to which it is being exported to downstream ecosystems.Today, around 60% of organic aerosols are derived from anthropogenic activities, indicating that organic deposition has also increased dramatically since the industrial revolution. Therefore, if the organics found on, within and being exported from Gulf of Alaska glaciers are from aerosols, the glacier ecosystem structure we observe today is fed by the waste products of industrial activity occurring thousands of miles away. If this is the case, then the organic carbon which is exported to ecosystems downstream of glaciers would also be of anthropogenic origin, suggesting these receiving ecosystems are also transformed relative to their pre-industrial status. As deposition of combustion products is a global phenomenon, all ecosystems may be receiving this ancient, labile carbon subsidy. In warmer ecosystems, the labile carbon windfall is presumably rapidly processed and its signal is lost. In frigid glacier environments, these inputs stand out, making glaciers sentinel ecosystems for the detection and study of anthropogenic deposition. Although the study focuses upon glaciers along the Gulf of Alaska, findings will be relevant to any ecosystem receiving depositional inputs. The project provides a highly interdisciplinary and collaborative research environment from which the undergraduates from under-represented groups in science, a masters student, and a postdoctoral researcher will all benefit. The collaboration extends beyond the funded US scientists to include German colleagues supported by the Max Planck Institute's Marine Geochemistry Group. This international component expands the possibilities for knowledge transfer and provides the US-based researchers access to unique, state-of-the-art analytical facilities. Results will be disseminated to the public through the U.S. Forest Service Mendenhall Glacier Visitor Center in Juneau, providing an opportunity for public outreach on the effects of climate change on glaciers.