How thick is Antarctic ice, and what is underneath?

Ice at the edge of the Antarctic continent hosts a flourishing ecosystem. Seals and penguins breed, fish mature, and algae thrive, all thanks to sea ice tethered to the shore, called fast ice. To understand how fast ice protects this ecosystem and to assess the area's health and future, scientists need to gauge how thick shore-bound ice is along the different parts of the coast—an estimate that has eluded scientists in the past.