OS22B-01
Reconstructing Methane Emission Events in the Arctic Ocean: Observations from the Past to Present

Tuesday, 15 December 2015: 10:20
3009 (Moscone West)
Giuliana Panieri, University of Troms, Troms, Norway, Jurgen Mienert, Univ Tromso, Tromso, Norway, Daniel J Fornari, Organization Not Listed, Washington, DC, United States, Marta E Torres, Oregon State Univ, College of Earth, Ocean, and Atmospheric Sciences, Corvallis, OR, United States, Aivo Lepland, CAGE – Centre for Arctic Gas Hydrate, Environment and Climate, UiT The Arctic University of Norway, Department of Geology, Tromsø, Norway and Scientific Party of CAGE 15-2
Abstract:
Methane hydrates are ice-like crystals that are present along continental margins, occurring in the pore space of deep sediments or as massive blocks near the seafloor. They form in high pressure and low temperature environments constrained by thermodynamic stability, and supply of methane. In the Arctic, gas hydrates are abundant, and the methane released by their destabilization can affect local to global carbon budgets and cycles, ocean acidification, and benthic community survival. With the aim to locate in space and time the periodicity of methane venting, CAGE is engaged in a vast research program in the Arctic, a component of which comprises the analyses of numerous sediment cores and correlative geophysical and geochemical data from different areas.

Here we present results from combined analyses of biogenic carbonate archives along the western Svalbard Margin, which reveal past methane venting events in this region. The reconstruction of paleo-methane discharge is complicated by precipitation of secondary carbonate on foraminifera shells, driven by an increase in alkalinity during anaerobic oxidation of methane (AOM). The biogeochemical processes involved in methane cycling and processes that drive methane migration affect the depth where AOM occurs, with relevance to secondary carbonate formation. Our results show the value and complexity of separating primary vs. secondary signals in bioarchives with relevance to understanding fluid-burial history in methane seep provinces.

Results from our core analyses are integrated with observations made during the CAGE15-2 cruise in May 2015, when we deployed a towed vehicle equipped with camera, multicore and water sampling capabilities. The instrument design was based on the Woods Hole Oceanographic Institution (WHOI) MISO TowCam sled equipped with a deep-sea digital camera and CTD real-time system. Sediment sampling was visually-guided using this system. In one of the pockmarks along the Vestnesa Ridge where high methane discharge was measured, we deployed the CAGE 888 marker as our first step in conducting time series studies to establish temporal variability going forward.

This research is partially supported by the Research Council of Norway through its Centres of Excellence funding scheme, project number 223259.

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