Detection of Methane Ebullition in Shelf Waters of the Laptev Sea in the Eastern Arctic Region

摘要

Methane is transported through the water column either by diffusion or in the form of bubbles [1]. Diffusion transport is determined by gradients of methane concentrations, which gradually change from maximal values in bottom waters to minimal (discharge) in the surface layer (main flow). The diffusion process is slow, which is responsible for oxidation of a significant share of dissolved methane particularly at large depths. Bubble transport is realized owing to solitary bubbles, which transfer methane from bottom sediments, when its production exceeds the solubility threshold in interstitial waters. Such solitary seepages of biogenic methane produced in surface sediments are regularly distributed through time and space to produce its elevated concentrations in the bottom water layer. In the case of its discharge, methane produced at deeper levels demonstrates more compact localization. Bubble transport is also realized in the form of mass accumulations of methane bubbles, which persistently or intermittently enter the water column to saturate its intermediate and near-surface layers. On shallow shelves characterized by the discharge of methane from decomposed gas hydrates, such blowouts may reach the atmosphere to form anomalously high concentrations above the surface waters [2].