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

该奖项由极地计划办公室南极地质和地球物理计划提供，支持一项研究南极干旱山谷地区低温化学和物理风化过程的合作研究计划。化学风化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”可以通过控制大气中这种重要温室气体的浓度来造成气候变化。由于控制化学风化速率的主要因素是温度和湿度，因此人们认为在气候较温暖的地区会发生化学风化增强。分析了南极洲泰勒谷(~78度)一些短暂溪流的地球化学特征。这些溪流每年流动4至10周，并与以干为基础的冰川有关。化学风化产生的溶质，如主要的阳离子、次要元素(如：锶、铯、锂、锶和钡)、重碳酸盐和溶解的活性二氧化硅，以及同位素(~(87)Sr/~(86)Sr)表明，这些极地沙漠小溪确实发生了化学风化。尽管风化的机制/过程尚不清楚，但人们推测，冰冻/融化循环的高度重合和/或这些河流中潜流带的异常水文行为是计算出高化学风化速率的原因。在这项提案中，计划在麦克默多干河谷长期生态研究(MCM-LTER)团队和其他人的初步工作的基础上，通过阐明通过低温过程的物理风化对化学风化的作用，更好地建立风化速率和风化机制。泰勒谷的邦尼湖盆地和莱特谷的玛瑙山谷的溪流中的悬浮物将被分析其总体化学成分，并与山谷中的岩石类型进行比较，以确定哪些物质正在被风化。重点将放在利用铀系地球化学来更好地查明溶质来源。将进行实验室实验，以确定通过冻融循环进行的微破裂对化学风化的作用。泰勒谷和莱特谷的主要岩石类型将被用于这些实验。所有这些数据将被用来类比地球在更冷、更干燥的气候条件下的历史风化制度。

0087915LyonsThis 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.