Satellite altimeter observed surface water increase across lake-rich regions of the Arctic

On our planet, the Arctic region has numerous and widely distributed lakes. These lakes are fundamental components of regional water cycles, carbon cycles, and the energy balance and also play a crucial role in providing habitats for wildlife, maintaining biodiversity, and supplying freshwater. According to satellite observations, in situ measurements, and climate models, the Arctic is the fastest-warming region on Earth. However, up to date, it is still unclear how lakes in the Arctic have responded to the rapid warming climate over the past decades. This suggests a strong need for detecting temporal changes in lakes across the Arctic in order to better monitor regional water resource dynamics, understand the potential drivers, and evaluate ecological and socio-economic influence.

Recently, Webb et al.1 investigated surface water area changes across lake-rich regions in the Arctic during the period 2000–2021 by detecting trends in the superfine water index (SWI) based on 500-m moderate resolution imaging spectroradiometer (MODIS) satellite imagery. Their results indicate that the net change in SWI was negative, and 82% of permafrost regions exhibited a decreasing trend in water areas.1 However, Olthof et al.2 argued Webb et al.’s study and concluded that results from Webb et al.1 that show widespread Arctic surface water declines may not be reliable due to properties of the MODIS SWI index, including its coarse spatial resolution to depict the surface water extent, its sensitivity to vegetation changes and water turbidity, and a relatively weak relationship with higher-resolution surface water cover. Considering these potential limitations in Webb et al.’s study, more robust evidence for observing surface water dynamics in the Arctic is urgently required.