Methane seep in Arctic Lake Qalluuraq. A, Surface bubbling of lake above methane seep. B, 83-kHz seismic-reflection profile of lake-bottom depression at seep and methane bubbles (m) in water column. Horizontal black lines are depth markers, spaced at 2.5-ft intervals. Vertical scale is exaggerated in this profile. Depression is approximately 3 m across and 2.5 m deep, according to independent information provided by UAF colleagues. C, Sidescan-sonar image showing lakebed pockmark associated with seep.