The retreat of the permafrost line during the interglacial maximum

Accelerated CH4 emissions in permafrost regions. The CH4 emissions in permafrost regions are mainly from CH4 reservoirs under frozen soil/ice. The PLIM is defined as the edge of a permafrost region that has not been disturbed during the glacial-interglacial period in the last 1 million years. Pushed by fossil fuel combustion, the PLIM is now retreating, and consequently intensified CH4 emissions. Methane emissions and unstable reservoirs are shown as pink arrows and clots. Carbon dioxide formed through CH4 oxidation is denoted by gray arrows.