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4 results on '"Kodovska, Fenix Garcia-Tigreros"'

1. Methane transport from the active layer to lakes in the Arctic using Toolik Lake, Alaska, as a case study

Author

Paytan, Adina, Lecher, Alanna L, Dimova, Natasha, Sparrow, Katy J, Kodovska, Fenix Garcia-Tigreros, Murray, Joseph, Tulaczyk, Slawomir, and Kessler, John D

Subjects
Earth Sciences, Geology, Climate Action, methane, Arctic lakes, active layer, radioisotope tracers, permafrost
Abstract

Methane emissions in the Arctic are important, and may be contributing to global warming. While methane emission rates from Arctic lakes are well documented, methods are needed to quantify the relative contribution of active layer groundwater to the overall lake methane budget. Here we report measurements of natural tracers of soil/groundwater, radon, and radium, along with methane concentration in Toolik Lake, Alaska, to evaluate the role active layer water plays as an exogenous source for lake methane. Average concentrations of methane, radium, and radon were all elevated in the active layer compared with lake water (1.6 × 10(4) nM, 61.6 dpm⋅m(-3), and 4.5 × 10(5) dpm⋅m(-3) compared with 1.3 × 10(2) nM, 5.7 dpm⋅m(-3), and 4.4 × 10(3) dpm⋅m(-3), respectively). Methane transport from the active layer to Toolik Lake based on the geochemical tracer radon (up to 2.9 g⋅m(-2)⋅y(-1)) can account for a large fraction of methane emissions from this lake. Strong but spatially and temporally variable correlations between radon activity and methane concentrations (r(2) > 0.69) in lake water suggest that the parameters that control methane discharge from the active layer also vary. Warming in the Arctic may expand the active layer and increase the discharge, thereby increasing the methane flux to lakes and from lakes to the atmosphere, exacerbating global warming. More work is needed to quantify and elucidate the processes that control methane fluxes from the active layer to predict how this flux might change in the future and to evaluate the regional and global contribution of active layer water associated methane inputs.

Published
2015

3. Assessing the influence of aerobic methane oxidation on ocean carbon dioxide and pH

Author

Kodovska, Fenix Garcia-Tigreros, Kessler, John, Kodovska, Fenix Garcia-Tigreros, and Kessler, John

Abstract

Thesis (Ph. D.)--University of Rochester. Department of Earth and Environmental Sciences, 2019., Beyond the oceanic uptake of anthropogenic carbon dioxide (CO2), feedbacks driven by a warming climate may enhance ocean acidification through the mobilization of old carbon stores that become CO2. These feedbacks include the remineralization of organic carbon (OC) in thawing permafrost, the oxidation of methane (CH4) produced from this newly thawed OC, or the destabilization of gas hydrates. While previous measurement and modeling studies have investigated ocean acidification, to date, no study has directly fingerprinted all sources of mobilized relic carbon contributing to this pH decline. This dissertation provides the first comprehensive study to fingerprint each potential source of carbon contributing to ocean acidification. We incorporate concentration and natural radiocarbon measurements of dissolved inorganic carbon (DIC), atmospheric CO2, dissolved organic carbon, particulate organic carbon, and CH4 to partition each CO2 end-member. This investigation focuses in two contrasting regions that are experiencing active CH4 release and are susceptible to climate change: the U.S Mid-Atlantic Shelf, an upper continental slope region with known CH4 seeps at the upper boundary of gas hydrate stability, and the Beaufort Sea Shelf in the Alaskan Arctic, a near-shore shelf region with both relic and thawed subsea permafrost and gas hydrates stores. Results from the U.S Mid-Atlantic Shelf show that in regions of active CH4 seepage and elevated CH4 concentrations, a small but quantifiable fraction of ancient-CH4 derived carbon is being assimilated into DIC (mean fraction of 0.6 ± 0.4%). Results from the Beaufort Sea Shelf show that CH4 and OC are exerting a larger influence and the lowest pH coincided with the largest fractions of old carbon (~11%), with noticeable contributions from remineralized OC and CH4 (up to 26.9 ± 19.1% and 8.9 ± 6.3%, respectively). Overall our results suggest that over short timescales of less than a year, CH4 oxidation in upper continental slop

Published
2021

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