HR: 0800h
AN: GC51D-1091    [Abstracts]
TI: Ocean Warming and Biochemical Effects of Dissociation of Oceanic Methane Hydrates
AU: * Lai, C A
EM: cal@LANL.GOV
AF: Los Alamos National Laboratory, EES-2, MS-J577, Los Alamos, NM 87545 United States
AB: Ocean exploration during last two decades indicates that huge deposits of oceanic methane hydrate (MH) exist on the seafloor on continental margins. MH transforms into water and methane (CH4) gas when it dissociates. After MH dissociates, CH4 gas is entrapped in bubbles coated with films of microbial. Evidences indicate that a great population of tiny bubbles flows with ocean currents at intermediate depth instead of rising to the ocean surface. This provides the time for microbes (methane oxidation bacteria) to consume the CH4. Earlier observations of CH4 bubbles in swamp and those generated from hydrothermal vents indicate that a great portion of CH4 has been oxidized before the bubbles rise to water surface. The chemical energy (heat) from oxidizing CH4 is released step-by-step following the chemical reactions and transferred from one organism to another through out the food chain. As long as the final products are water and CO2, the total heat to be generated will be conserved in the water mass no matter what processes take place. The energy density is low due to diffusion, but the yield (~195 Kcal/mole of CH4) remains the same. The oxidation of CH4 causes a depletion of dissolved oxygen (O2) in seawater near (and above) MH dissociation level. Ocean observations reflect this biochemical mechanism with a distinct core of minimum dissolved O2 within major ocean currents (like Gulf Stream) flowing over known methane hydrate deposits (like Blake Ridge). The additional heat generated through this micro-biochemical process is sufficient to cause the trend of ocean warming during last 5 decades since the advent of modern ocean observation. The biochemically generated extra heat is carried by Gulf Stream into Arctic Ocean and that complements the atmospheric heat fluxes in thawing the basin's sea ice by the observed thickness. Therefore, it is hypothesized that this micro-biochemical warming of oceans might be one of the factors causing the global warming in the geological past.
DE: 4806 Carbon cycling
DE: 4215 Climate and interannual variability (3309)
DE: 1050 Marine geochemistry (4835, 4850)
DE: 1615 Biogeochemical processes (4805)
DE: 1635 Oceans (4203)
SC: Global Climate Change [GC]
MN: 2004 AGU Fall Meeting