It soon became too dark to see A-74, which covered 1,270 km², as the Antarctic winter set in. But Landsat 8 continued imaging with its Thermal Infrared Sensor (TIRS). The imagery is visibly dark, but TIRS detects temperature on the surface.

TIRS shows relatively cooler temperatures darker than warmer temperatures, so the iceberg and ice shelf appear black. Clouds are relatively warmer than ice, so clouds sometimes cover the ice with swaths of gray.

TIRS reveals what could not be seen in the darkness. The iceberg separates from the ice shelf, moves away, then bumps back into it before drifting south. In August 2021, in a timeframe of less than 2 weeks, the berg spun around the tip of Brunt Ice Shelf, brushed past it, rotated counterclockwise, and continued south. Landsat 8 spotted it with its visible bands in February 2022 much farther south along the Antarctic coast.

It’s unknown exactly how the ice shelf will respond to the 2021 North Rift calving. The situation is being monitored closely by Landsat along with Sentinel, WorldView, ground-penetrating radar, drone imagery, and a network of GPS stations.