SAR-based lake ebullition maps. Panel a shows Alaska study regions with SAR footprints outlined in yellow. Subsequent panels show SAR-based CH4 ebullition maps for b) Barrow Peninsula, c) Atqasuk, d) Toolik, e) northern Seward Peninsula, and f) Fairbanks. Study lakes with field-based measurements are outlined (b,c) or boxed (d,e,f) in white. Orange boxes in panel f indicate anthropogenic study lakes.

ACT-America 2019 summer airborne campaign showing the flight paths for the two aircrafts and location of ground towers. Flights were concentrated on three study domains: northeast, south-central, and midwest regions of the United States.

Left: The DLR Falcon used for the SALTRACE 2013 and the A-LIFE 2017 campaigns. Right: The NASA DC-8 aircraft used during the ATom missions sitting at the Pago Pago International Airport, American Samoa.

Sixteen measurement sites located across interior Alaska, USA, and at one site in Yukon, Canada. Sites C17K, C26K, E23, F17, H31, and I17 are collocated with the seismic stations.

Site sampling plan used for characterizing active layer soils (left). Axes are in meters. At Imnavait Creek, active layer thickness (ALT) was measured on transects intersecting a central soil pit. Soil dielectric properties, in situ moisture and temperature profiles were measured, and soil samples were collected for analyses from the soil pit (right).