Ocean stratification and sea-ice cover in Barents and Kara seas modulate sea-air methane flux: satellite data

• Main Authors: Yurganov, Leonid, Carroll, Dustin, Pnyushkov, Andrey, Polyakov, Igor V, Zhang, Hong
• Format: Article in Journal/Newspaper
• Language: English
• Published: Polar Research Institute of China - PRIC 2021
• Subjects: Atmosphere; Cryosphere; Oceans; Arctic; Barents Sea; Kara Sea; Advances in Polar Science; North Atlantic; Polar Science; Sea ice
• Online Access: http://library.arcticportal.org/2750/; http://library.arcticportal.org/2750/1/A2102005.pdf

The diverse range of mechanisms driving the Arctic amplification and global climate are not completely understood and, in particular, the role of the greenhouse gas methane (CH4) in the Arctic warming remains unclear. Strong sources of methane at the ocean seabed in the Barents Sea and other polar regions are well documented. Nevertheless, some of those publications suggest that negligible amounts of methane fluxed from the seabed enter the atmosphere, with roughly 90% of the methane consumed by bacteria. Most in situ observations are taken during summer, which is favorable for collecting data but also characterized by a stratified water column. We present perennial observations of three Thermal IR space-borne spectrometers in the Arctic between 2002 and 2020. According to estimates derived from the data synthesis ECCO (Estimating the Circulation and Climate of the Ocean), in the ice-free Barents Sea the stratification in winter weakens after the summer strong stability. The convection, storms, and turbulent diffusion mix the full-depth water column. CH4 excess over a control area in North Atlantic, measured by three sounders, and the oceanic Mixed Layer Depth (MLD) both maximize in winter. A significant seasonal increase of sea-air exchange in ice-free seas is assumed. The amplitude of the seasonal methane cycle for the Kara Sea significantly increased since the beginning of the century. This may be explained by a decline of ice concentration there. The annual CH4 emission from the Arctic seas is estimated as 2/3 of land emission. The Barents/Kara seas contribute between 1/3 and 1/2 into the Arctic seas annual emission.