Satellite Year-Round Methane Measurements for the Arctic: Towards
Elucidation of Methane Growth After 2014
Abstract
On decadal timescales, the greenhouse gas methane (CH4) is
~100 times more potent than carbon dioxide. Its
abundance is increasing, many of its sources are temperature dependent.
The Arctic is the site of the fastest warming globally. Feed-backs
between Arctic temperature and CH4 emissions and concentrations need
investigation. Unfortunately, available Arctic in situ data are
extremely sparse with no marine observations outside summer. Satellite
instruments measuring solar radiation reflected from the surface are
ineffective in the Arctic. Thus, we leverage satellite data from AIRS,
IASI-1, and IASI-2 Thermal Infrared (TIR) spectrometers, which provide
year-round, day/night CH4 observations. Available in situ high latitude
NOAA/ESRL surface coastal (50-85°N) flask atmospheric CH4 concentrations
were compared with satellite data. We find: 1) remote sensing data
revealed 150% (IASI-1, mid-upper troposphere) and 80% (surface data
for Arctic stations) increases in atmospheric CH4 concentration growth
rates between 2010-2014 and 2014-2017 time spans. Global NOAA/ESRL
surface concentration rates increased by 90% for the same period; 2)
maximum CH4 seasonal emission from the Arctic land occurs in boreal
summer, while that from the Barents Kara Sea (BKS) occurs in boreal
winter (Nov–Mar). Total annual Arctic Ocean CH4 emissions are
preliminary estimated as ~40% of all land emissions
North of 50°N; 3) marine emissions are concentrated in shelf areas
within ~100 km of the coasts of major Arctic BKS lands;
4) CH4 anomalies over BKS, defined as surplus over its concentration at
the North Atlantic area, grew after 2014; 5) the strongest SST increase
was observed every year in the southeast Barents Sea in June due to
strengthening of the warm Murman Currents and in the south Kara Sea in
Sept. Direct in situ CH4 flux measurements during polar night over sea
are necessary to test the satellite results.