RAPID: The effect of methane laden oil on climate and dissolved oxygen: using the Deepwater Horizon oil spill as an analog for clathrate decomposition and seeping methane

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The large fossil methane (CH4) discharged from the destroyed Deepwater Horizon rig in the Gulf of Mexico (between 2-100 × 106 moles of CH4 per day) provides a unique opportunity to determine the impact of methane on dissolved oxygen concentrations and assess its burden on the atmosphere. Without considering ebullition effects, preliminary calculations indicate that a 10% reduction of dissolved oxygen can be achieved in the low oxygen zones of the Gulf of Mexico in 4 - 190 days at the estimated methane fluxes.With funding from this NSF Rapid Response Research (RAPID) award, researchers from Texas A&M University in collaboration with a scientist from Yale University, will analyze water column samples for methane concentrations and stable isotopes, as well as measure the air-sea flux of methane, ethane, propane, carbon dioxide and del13C-CO2. In addition, dissolved oxygen measurements, methane oxidation rates, and the effect of microbial community structure on methane, oil, and oxygen concentrations will be assessed. Results will be used to test the following hypotheses: (1) Significant and quantifiable amounts of methane released rapidly from naturally decomposing oceanic clathrate hydrates will be both dissolved in the water column and emitted to the atmosphere, and (2) The oxidation and ebullition of methane in the water column will significantly contribute to the low oxygen zones in the northern Gulf of Mexico. Even though geochemical data has shown significant clathrate decomposition in the past, little, if any, information is available of whether methane released during these events entered the atmosphere or was retained in the ocean. This deepwater anthropogenic spill of oil and methane into the Gulf of Mexico can be used as an analog for a natural rapidly decomposing clathrate hydrate and provide much needed information on the fate of methane released during these past events. The broader impacts of this proposal include the involvement of two graduates and one undergraduate student, as well as yield insights into the impact of the massive fossil methane released to the Gulf of Mexico by the Deepwater Horizon rig.