Collaborative Research: Chemical Weathering in Taylor Valley Stream: Sources, Mechanisms and Global Implications

0087994 McKee该奖项由极地项目办公室南极地质和地球物理项目提供，支持一项合作研究计划，研究南极洲干谷地区的低温化学和物理风化过程。化学风化作用被认为通过在硅酸盐水解等过程中消耗二氧化碳（CO2）来影响全球气候。这种二氧化碳“缓冲”可以通过控制这种重要温室气体的大气浓度来造成气候变化。由于化学风化速率的主要控制因素是温度和湿度，因此认为在温暖的气候中会发生化学风化增强。分析了南极泰勒谷（~78度）一些短暂溪流的地球化学。这些溪流每年流动4至10周，与干基冰川有关。化学风化产生的溶质，如主要阳离子、次要元素（如，铷、铯、锂、锶和钡）、碳酸氢盐和溶解的活性二氧化硅以及同位素（87 Sr/86 Sr）表明，这些极地沙漠溪流中确实发生了化学风化。虽然风化的机制/过程是未知的，据推测，无论是高度重合的冻/融循环和/或不寻常的水文行为的潜流区在这些流负责高化学风化率已计算。在本提案中，计划在麦克默多干谷长期生态研究（MCM-LTER）团队和其他人的初步工作基础上，通过阐明物理风化作用（通过低温过程）对化学风化的影响，更好地确定风化速率和风化机制。来自泰勒谷邦尼湖盆地和赖特谷玛瑙谷的溪流中的悬浮物将被分析其大量化学成分，并与山谷中的岩石类型进行比较，以确定哪些物质正在风化。重点将放在利用铀系地球化学，以更好地确定溶质来源。通过室内试验，研究冻融循环引起的微破裂对化学风化的影响。泰勒谷和赖特谷的主要岩石类型将用于这些实验。所有的数据都将被用来类比地球上更冷、更干燥的气候条件下的历史风化状况。

0087994McKeeThis award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, supports a collaborative research program to study low temperature chemical and physical weathering processes in the Dry Valleys region of Antarctica. Chemical weathering is thought to affect global climate by consuming carbon dioxide (CO2) during processes such as silicate hydrolysis. This CO2 "buffer" can create climate change by controlling the atmospheric concentration of this important greenhouse gas. Because the principle controls on chemical weathering rates have been argued to be temperature and moisture, enhanced chemical weathering is thought to occur in warmer climates. The geochemistry of a number of ephemeral streams in Taylor Valley, Antarctica (~78 degrees) has been analyzed. These streams flow for 4 to 10 weeks per year and are associated with dry-based glaciers. Solutes produced from chemical weathering such as major cations, minor elements (e.g., rubidium, cesium, lithium, strontium, and barium), bicarbonate and dissolved reactive silica, as well as isotopes (87Sr/86Sr) indicate that chemical weathering does occur in these polar desert streams. Although the mechanism/process of weathering is unknown, it is hypothesized that either the high coincidence of freezing/thawing cycles and/or the unusual hydrologic behavior of the hyporheic zone in these streams are responsible for the high chemical weathering rates that have been computed. In this proposal, the plan is to build upon the initial work of the McMurdo Dry Valleys Long Term Ecological Research (MCM-LTER) team and others by better establishing weathering rates and weathering mechanisms by elucidating the role of physical weathering via cryogenic processes on chemical weathering. The suspended matter in streams from the Lake Bonney basin in Taylor Valley, and the Onyx Valley in Wright Valley will be analyzed for their bulk chemistry and compared to rock types in the valleys to establish what materials are being weathered. Emphasis will be placed on the utilization of uranium series geochemistry to better ascertain solute sources. The laboratory experiments will be done to establish the role of microfracturing via freeze-thaw cycles on chemical weathering. Major rock types occurring in Taylor and Wright Valleys will be used for these experiments. All of the data will be used to draw analogies to historic weathering regimes on Earth during colder, drier climatic regimes.