Modeling of decomposition of subbottom methanehydrates under climatic changes at time scale of a few thousand years.
The observed synchronicity between temperature and methane concentrations in Greenland and Antarctica ice cores has raised the question of the role of methane in glacial-interglacial climate change. The release of methane from hydrate has been invoked to explain abrupt increases in the atmospheric concentration of methane during the last glacial cycle. The three-dimensional mathematical model of the dissolved gas transport by the ocean currents is used for the quantitative evaluation of the scale of a possible methane flux into the atmosphere from the decomposed subbottom methanehydrates. The climatic model of the ocean has been integrated for the period of 5000-10000 years and simulates penetrations of warming from the surface into the deep ocean. A three-dimensional equation of transport of dissolved methane from sources has been simultaneously solved. A few scenario experiments with different scales of the surface ocean temperature changes were carried out. The experiments have shown that changes of concentration of methane as a result of decomposition subbottom methanehydrates can be the consequence of temperature changes. Thus, long warming can result in destabilization of hydrates in a sedimentary layer of the ocean. The calculated methane flux into the atmosphere exceeded 18 Tg/year.