RPG: Toward a Model of Inorganic and Organic Carbon Fluxes Through a Cycle of Glacier Advance and Retreat

9706180安德森冰川对其入侵的景观产生了深远的影响。它们将河流山谷重塑成宽阔的u形山谷。它们形成了乳白色的溪流和明亮的蓝绿色湖泊，湖中充满了非常细的悬浮岩粉。这些物理效应源于冰川将基岩粉碎成细粒新鲜碎屑的独特能力。虽然人们认识到物理和化学风化过程是相互联系的，但在阐明冰川作用的化学影响方面所做的工作很少。由于冰川既使侵蚀过程的速率高于非冰川地区的侵蚀过程，又使地表物质的性质向较新鲜的沉积物转变，因此冰川很可能也改变了化学过程的速率和性质。目前，冰川对全球碳循环和气候变化的影响是未知的，也是有争议的。该项目为开发一个基于实地的定量模型奠定了基础，该模型对调节碳循环具有重要意义的高山冰川通量的影响，即风化速率和矿物表面积通量。风化作用驱动了碳循环的无机部分，矿物表面积最近被认为是有机碳埋藏的根本控制因素，从而控制了碳循环的有机碳部分。冰川前进时泥沙通量的变化，以及冰川后退时泥沙和冲水的搁浅，预计都将在调节这些通量方面发挥重要作用。这项工作将对冰川沉积物中的化学过程有必要的了解，并确定模型测试的最佳现场，最终目标是创建一个溶质通量模型，以利用加州大学圣克鲁斯分校和INSTAAR的其他人正在开发的冰川侵蚀模型。有了这样一个模型，我们将能够解决冰川造成的物理变化在多大程度上也改变了碳循环，并导致了全球气候变化。沉积物和溶质通量都直接影响碳循环。在海洋沉积物中，有机碳与矿物表面积密切相关，这意味着碳埋藏受沉积速率的强烈控制。因此，冰川作用改变侵蚀速率和到达海洋的沉积物粒度分布的程度对于确定有机碳埋藏速率很重要。一项勘察取样计划将解决向外冲刷平原的沉积物捕获效率以及下游悬浮沉积物粒度和矿物表面积的变化。无机碳通量是由矿物风化反应引起的。我们知道，在冰碛中，化学风化速率和锶同位素比值随着沉积物年龄的增加而降低。这项工作将使用实验室实验和实地观察来确定年轻冰川碎屑中的矿物风化反应，风化速率衰减的时间尺度，以及主要的风化反应如何随沉积物年龄变化。研究87Sr/86Sr等同位素代用物是否反映风化速率或风化过程是本次分析的重要组成部分。在这个研究规划项目中，我将确定一个详细的实地水和溶质通量测量方案的实地地点，并开发基于实地和实验室的算法来定量描述前冰川地区的悬浮沉积物和溶质通量。

9706180 Anderson Glaciers profoundly impact the landscapes they invade. They reshape fluvial valleys into broad U-shaped valleys. They produce milky streams and brilliant turquoise blue lakes laden with very fine suspended rock flour. These physical effects arise from the unique ability of glaciers to pulverize bedrock into fine-grained fresh debris. Although it is recognized that physical and chemical weathering processes are linked, little work has been done to elucidate the chemical impacts of glaciation. Because glaciers both increase the rate of erosion processes above those in non-glacial landscapes and alter the character of surface materials towards fresher deposits, it is likely that glaciers also change the rate and nature of chemical processes. At present, the influence of glaciers on the global carbon cycle and climate change is both unknown and debated. This project lays the groundwork for developing a field-based quantitative model of the effects of alpine glaciation fluxes important in regulating the carbon cycle, i.e., weathering rates and mineral surface area flux. Weathering drives the inorganic portion of the carbon cycle, and mineral surface area has been recognized recently as a fundamental control on organic carbon burial, and thus the organic carbon portion of the carbon cycle. The change in sediment flux as a glacier advances, and the stranding of till and outwash as a glacier retreats, are both expected to play important roles in modulating these fluxes. This work will develop the necessary understanding of the chemical processes in glacial sediments, and identify the best field sites for model testing, with the ultimate goal of creating a solute-flux model to piggy-back on a glacial erosion model in development by others at UC Santa Cruz and INSTAAR. With such a model in hand, we will be able to address the extent to which the physical change wrought by glaciers also alters the carbon cycle and contributes to global climate change. Both sediment and solute fluxes directly influence the carbon cycle. In marine sediments, organic carbon is strongly correlated with mineral surface area, meaning that carbon burial is strongly controlled by sedimentation rates. Therefore the degree to which glaciation alters erosion rates and the grain size distributions of sediments reaching the ocean is important in setting organic carbon burial rates. A reconnaissance sampling program will address the sediment trapping efficiency of outwash plains and the downstream changes in suspended sediment grain size and mineral surface area. Inorganic carbon fluxes are due to mineral weathering reactions. We know that both chemical weathering rates and strontium isotopic ratios decrease with sediment age in glacial moraines. This work will use both lab experiments and field observations to establish mineral weathering reactions in young glacial debris, the time-scale for the decay in weathering rates, and how predominant weathering reactions vary with sediment age. As an important part of this analysis is to explore whether isotopic proxies, such as 87Sr/86Sr, reflect weathering rates or weathering processes. In this research planning project, I will identify a field site for a detailed program of field measurement of water and solute fluxes, and develop field and lab-based algorithms to describe quantitatively the suspended sediment and solute fluxes from a proglacial area.