Methane bubbles in thermokarst lake ice. When ice-rich permafrost thaws, former tundra and forest turns into a thermokarst lake as the ground subsides. The carbon stored in the formerly frozen ground is consumed by the microbial community, who release methane gas. When lake ice forms in the winter, methane gas bubbles are trapped in the ice. These processes are being studied for how they are affected by climate change and how they can contribute to global warming by directly and indirectly releasing gases such as methane and carbon dioxide. Image published in 2018.