Satellite ice extent, sea surface temperature, and atmospheric methane
trends in the Barents and Kara Seas
Abstract
Large positive anomalies in lower troposphere methane
(CH4) in early fall of nearly every year (2003 to 2015)
led to an average atmospheric CH4 growth of 3.06 to 3.49
ppb yr-1 for the Barents and Kara Seas (BKS). At the
same time, sea surface temperature (SST) increased from 0.0018 to
0.15 °C yr-1 while sea ice coverage decreased. Large
positive CH4 anomalies were discovered around Franz
Josef Land (FJL) and offshore west Novaya Zemlya with smaller
CH4 enhancement and growth near Svalbard, downstream and
north of known seabed CH4 seepage. The strongest
SST increase each year was in the southeast Barents Sea in June
due to strengthening of the warm Murman Current (MC) and in the south
Kara Sea in September. We propose that atmospheric CH4
increase is occurring due to seepage from the petroleum reservoirs
underlying the BKS and thawing of subsea permafrost and hydrates which
then ventilates to the atmosphere from seasonal deepening of the surface
ocean mixed layer and also from “methane shoaling” where currents
transport deep water CH4 into shallower waters.
Continued strengthening heat transfer by the MC to the BKS will
contribute to further warming (with the Barents Sea projected ice-free
around 2030) and marine CH4 emissions to the atmosphere.