Environmental Science
Thermokarst Lakes and Permafrost Lowlands
Quick fact
In some regions of Siberia and Alaska, thermokarst lakes can expand by more than 20 meters per year, consuming the surrounding landscape.
Why this is interesting
You've probably seen pictures of circular ponds in the Arctic tundra. But did you know these lakes are actively carving the ground beneath them, and a single summer of warming can cause the land to slump and sink?
Read the full explanation
Understanding Thermokarst Lakes and Permafrost Lowlands
Imagine a huge ice cube buried just below the ground. In permafrost, this ice is locked in the soil. When the ice melts, the ground above it loses support and collapses, creating a depression. Water from melted ice or rain fills the depression, forming a lake. This is thermokarst. Over time, the lake expands, and the edges keep thawing more ice, making the lake grow. It's like a slow-motion sinkhole, but on a massive scale, reshaping flat lowlands into a patchwork of ponds and lakes.
A deeper explanation
The process begins when surface disturbance—from wildfire, warming, or human activity—exposes permafrost to warmer temperatures. Thawing ice-rich permafrost reduces soil volume, causing the ground to sink (thermokarst). Meltwater collects in the depression, and the lake water absorbs solar energy, warming the underlying and surrounding permafrost. This creates a positive feedback loop: warmer water thaws more permafrost, which expands the lake and creates more water. As lakes grow, they can coalesce, drain, or partially drain, leaving behind distinctive basins that fill with peat and vegetation. Additionally, thawing permafrost releases organic carbon, which microbes convert to methane and carbon dioxide, amplifying greenhouse gas emissions. This reshaping is crucial because it changes drainage patterns, affects wildlife habitats, and contributes to permafrost carbon feedback, making it a key player in global climate change.