CO2 evasion from the Greenland ice sheet

点击翻译按钮获取中文摘要

Total freshwater runoff from the Greenland ranks among the 12th and 13th largest rivers of the world, yet analyses of its geochemistry are surprisingly sparse. Insufficient data are available to identify what carbon cycle feedbacks presently occur and how they might change in the future. Preliminary research suggests that rivers draining the Greenland Ice Sheet yield a previously unknown flux of CO2 to the atmosphere: water emerging from beneath the Russell Glacier in West Greenland has CO2 partial pressures 3 to 10 times supersaturated with respect to atmospheric equilibrium, likely originating from subglacial microbial metabolism. Despite consumption through chemical weathering during downstream transport, some of this CO2 evades to the atmosphere. Key questions concern if, how, and to what extent CO2 evasion will either increase or decrease as the ice sheet decays in a warmer world. Through seasonal samplings and targeted hypothesis testing, this project aims to improve understanding of modern-day processes. The work would focus on a source-to-sink characterization of the Akuliarusiarsuup Kuua River, from its origin at the terminus of the Russell Glacier to its mouth at the head of the Kangerlussuaq Fjord. The objective is to measure and model downstream gradients for pH, major ions, dissolved organic carbon, carbonate system parameters, and the carbon isotope composition of dissolved inorganic carbon. In addition, the oxygen and hydrogen isotope composition of water will be used to identify water sources and flow paths, and the radiocarbon content of dissolved inorganic and organic carbon will constrain the age of the carbon. These data would be used to test five hypotheses designed to elucidate how microbial activity, hydrologic processes, and chemical weathering regulate the magnitude of CO2 evasion. In addition to teaching and training a Ph.D. graduate student, the PI would advise undergraduate student researchers who would conduct fieldwork and write senior honors theses. The PI and his student group would also engage K-12 underrepresented minorities in education and outreach activities illustrating the greenhouse effect and its relationship to the proposed study.