YEAR-ROUND DETERMINATION OF METHANE (CH4) SOURCES AND SINKS IN ARCTIC LAKES USING CONTINUOUS AND AUTONOMOUS SAMPLING

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dc.contributor.advisorLapham, Laura Len_US
dc.contributor.authorMcIntosh Marcek, Hadleyen_US
dc.contributor.departmentMarine-Estuarine-Environmental Sciencesen_US
dc.contributor.publisherDigital Repository at the University of Marylanden_US
dc.contributor.publisherUniversity of Maryland (College Park, Md.)en_US
dc.date.accessioned2020-07-13T05:35:36Z
dc.date.available2020-07-13T05:35:36Z
dc.date.issued2020en_US
dc.description.abstractMethane (CH4) is a potent greenhouse gas and its concentration has been increasing in the atmosphere. While natural emissions from inland water bodies are known to be important, there is large uncertainty in the amount of methane released from lakes to the atmosphere, especially from Northern latitudes. Part of this is due to limited sampling in these systems during dynamic periods, such as ice-over and ice-melt. To better understand these temporal dynamics, I used autonomous, continuous samplers (OsmoSamplers) to collect lake water year-round over two years (2015-2017). Lake water was collected at a fine temporal resolution to provide time-integrated (~1 week) samples from multiple Arctic lakes within the Mackenzie Delta. The Mackenzie Delta is a lake-rich, productive environment that is expected to be a significant source of methane to the atmosphere. Lakes spanning the central delta and outer delta were sampled for methane concentration and stable carbon isotope ratio (δ13C-CH4) changes, ion concentrations, and water column characteristics were measured with continuous sensor data (temperature, water pressure, conductivity, light, and dissolved oxygen). These unique time-series datasets show lakes exhibit a close coupling of dissolved oxygen, and other electron acceptors, with the timing of methane increasing during ice-cover. The increase in methane concentrations is primarily from diffusion out of sediments and possibly water-column methanogenesis. One lake in the outer delta exhibited thermogenic gas bubble dissolution that contributed to under-ice methane concentration increases. Following ice-melt, lake depth appears to impact methane release to the atmosphere. Shallower lakes exhibit rapid fluxes followed by significant microbial methanotrophy. Deeper lakes in the central delta are connected to groundwater, though it does not appear groundwater transports methane. This is the first study of dissolved methane and gas bubble 14C-age in the Mackenzie Delta and shows that dissolved methane is produced primarily from modern carbon sources, such as macrophyte biomass and terrestrial material, but some methane transported in gas bubbles is significantly older, with seeps in the outer delta rapidly releasing radiocarbon-dead, thermogenic methane. This study demonstrates the importance of multi-lake studies particularly with fine scale temporal sampling to understand methane processes in seasonally ice-covered lakes.en_US
dc.identifierhttps://doi.org/10.13016/luol-c9hv
dc.identifier.urihttp://hdl.handle.net/1903/26266
dc.language.isoenen_US
dc.subject.pqcontrolledGeochemistryen_US
dc.subject.pqcontrolledChemical oceanographyen_US
dc.subject.pquncontrolledDiffusionen_US
dc.subject.pquncontrolledLakesen_US
dc.subject.pquncontrolledMackenzie Deltaen_US
dc.subject.pquncontrolledMethaneen_US
dc.subject.pquncontrolledOsmoSampleren_US
dc.subject.pquncontrolledRadiocarbonen_US
dc.titleYEAR-ROUND DETERMINATION OF METHANE (CH4) SOURCES AND SINKS IN ARCTIC LAKES USING CONTINUOUS AND AUTONOMOUS SAMPLINGen_US
dc.typeDissertationen_US

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