Satellite ice extent, sea surface temperature, and atmospheric methane trends in the Barents and Kara seas

Abstract. Long-term (2003–2015) satellite-derived sea-ice extent, sea surface temperature (SST), and lower tropospheric methane (CH₄) of the Barents and Kara Seas (BKS) were analyzed for statistically significant anomalies and trends for 10 focus areas and on a pixel basis that were related to currents and bathymetry. Large positive CH₄ anomalies were discovered around Franz Josef Land (FJL) and offshore west Novaya Zemlya in September. Far smaller CH₄ enhancement was around Svalbard, downstream of known seabed seepage.

Strongest SST increase was southeast Barents Sea in June due to strengthening of the warm Murman Current (MC) and in the south Kara Sea in September, when the cold Percey Current weakens. These regions and around FJL exhibit the strongest CH₄ growth. Likely sources are CH₄ seepage from subsea permafrost and hydrates and the petroleum reservoirs underlying the central and east Barents Sea and the Kara Sea. The spatial pattern was poorly related to depth, and better explained by shoaling. Peak CH₄ anomaly is several months after peak SST, consistent with a several month delay between SST and seabed temperature. Continued MC strengthening will increase heat transfer to the BKS, rendering the Barents Sea ice-free in about 15 years.