Modeling the fate of methane in the water column by model coupling

Estimates of atmospheric methane emissions due to seabed methane seepage are hard to constrain. Additionally, high concentrations of methane can have an impact on local biology due to local ocean acidification. In both cases, better tools for modeling the fate of methane in the water column are needed.  

We present a new approach where we include and couple a wide range of water column processes by using several already verified models in tandem, attempting to form a complete modelling framework for the fate of methane in the water column. Included processes are gas phase changes, advection, dilution, direct and diffusive atmospheric flux and microbial oxidation. The modelling framework allows for a complete estimate of atmospheric emissions, both direct and diffusive fluxes, as well as the 3-dimensional distribution of methane in the water column. The framework can be applied to specific seep sites of interest using hydroacoustic data as input. Additionally, it is also possible to simulate atmospheric fluxes in potential edge cases and future scenarios in areas where local seepage is expected to change or is unknown.

We tested the methodology using hydroacoustic field data from a seep site in the Hola trough offshore North-Western Norway in Spring 2020. We calculated both direct and diffusive atmospheric methane fluxes, distribution of methane in the water column and its potential for affecting local biology due to acidification.