Fig. 2: Chronological images and field photos of the North Star Yedoma (NSY) study site.
From: Upland Yedoma taliks are an unpredicted source of atmospheric methane
a 1949 single-band airborne optical image available through USGS Earth Explorer (https://pubs.usgs.gov/gip/AerialPhotos_SatImages/aerial.html). b 1996 image showing widespread thermokarst-mound formation. c 2020 image showing deciduous forest succession in the western regrowth section and grass in the eastern section. The timing of the initial disturbance (sometime between August 1976 and August 1978) was determined by comparing Landsat false color composites that indicated disturbance to vegetation within this time frame. Locations of the eddy-covariance tower (EC; 80% footprint white dotted line), geophysical observations (Lines A and D), and boreholes (BH) are shown in (c). d–f Ground photos of the EC tower in the study field (d), soil pit (e), and lowest portion of the 7-m-long soil core (f). Panels (e) and (f) show dry soil conditions near the ground surface [22–26% volumetric water content (VWC)], the base of the talik (26–30% VWC), and top of permafrost (21–26% VWC).
