Publication Date

Spring 2018

Advisor(s) - Committee Chair

Dr. Jason Polk, Dr. M. Royhan Gani, Dr. Thorsteinn Thorsteinsson

Degree Program

Department of Geography and Geology

Degree Type

Master of Science

Abstract

An investigation into the carbon dynamics and weathering processes occurring in Icelandic glacial-fed streams was conducted during the spring to summer seasonal transition in June of 2017. Four major outlet rives were sampled from the glaciers of Gígjökull, Steinsholtsjökull, Sólheimajökull, and Falljökull. Markarfljót, the major river that Gígjökull, Steinsholtsjökull, and many other glaciers drain into, was also sampled. Longitudinal sampling occurred at all sites to capture downstream trends in the hydrogeochemistry and carbon dynamics. Distinct differences in geochemistry between glacier surface meltwater, sub-glacial waters, pro-glacial lake water, and post-mixed downstream samples were evident in the data. Glacier surface streams were characterized by relatively colder water temperatures, lower specific conductivity, lower total dissolved solids (TDS) and ion concentrations, and more enriched δ13CDIC values than downstream samples. The THINCARB model was used to calculate the total dissolved inorganic carbon (TDIC), excess partial pressure of carbon dioxide (EpCO2), and percent contribution to TDIC by bicarbonate (HCO3), carbonate (CO3), and carbonic acid and dissolved CO2 (H2CO3). All sites showed a slight decreasing trend in DIC and EpCO2 downstream. The calculated CO2 flux ranged from 1.14 × 107 g/yr to 2.80 × 109 g/yr. The DIC flux ranged from 6.81 × 107 g/yr to 8.44 × 109 g/yr. The average carbon within the CO2 fluxing in these rivers accounts for 0.0004% of the annual, global flux of carbon. The δ13C values were the most variable throughout the study and indicate there are multiple sources influencing the river downstream. This study suggests that, despite previous assumptions and estimations, these glacial-fed rivers act as sources of CO2; however, the samples from this study only provide a snapshot into the carbon flux dynamics during the Spring to Summer seasonal transition. In most samples, HCO3 was the dominant species contributing to DIC content within the rivers, suggesting that DIC is being transported to the ocean as HCO3 but sourced to the atmosphere as CO2. By acting as sources of CO2 to the atmosphere, the process of glaciers melting, which drive geochemical processes within the rivers, are contributing to a positive feedback loop with respect to global warming.

Disciplines

Environmental Sciences | Fresh Water Studies | Geochemistry | Glaciology

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