Climate Signatures on Lake And Wetland Size Distributions in Arctic Deltas
The presence of abundant lakes is a defining characteristic of Arctic deltas and plays a key role in nutrient storage and flux through deltas. Many of these lakes are formed by the thawing of permafrost and the melting of ground ice. The characteristics of the lake sizes across deltas appear to vary with the climate of the delta indicating the changing to temperature may alter the number and size of lakes.
Quantifying how deltaic lake size distributions vary with climate will help to understand how lakes may change under future climate. Differences in size distributions between delta lakes and wetlands highlight different controls and potential responses to changing climate.
Arctic river deltas are landscapes facing significant risk from climate change, in part due to their unique permafrost features. In particular, thermokarst lakes in ice-rich permafrost are expected to both expand and drain under warming-induced permafrost thaw, reconfiguring delta hydrology and impacting the arctic carbon cycle. A limitation in understanding how thermokarst lake cover might be changing is the significant interannual variability in water cover in flat regions such as deltas, which makes it difficult to distinguish between perennially inundated, thermally relevant water bodies, and ephemerally inundated waterbodies. Here, we present a pan-Arctic study of 12 arctic deltas wherein we classify observed waterbodies into perennial lakes and ephemeral wetlands capitalizing on the historical record of remote sensing data. We provide evidence that thermokarst lake sizes are universally lognormally distributed and that historical temperature trends are encoded in lake sizes, while wetland sizes are power-law distributed and have no temperature trend. These findings pave the way for quantitative insight into lake cover changes on arctic deltas and associated carbon and hydrologic cycle impacts under future climate change.