Environmental Research Letters (Jan 2018)
The sign, magnitude and potential drivers of change in surface water extent in Canadian tundra
Abstract
The accelerated rate of warming in the Arctic has considerable implications for all components of ecosystem functioning in the High Northern Latitudes. Changes to hydrological cycle in the Arctic are particularly complex as the observed and projected warming directly impacts permafrost and leads to variable responses in surface water extent which is currently poorly characterized at the regional scale. In this study we take advantage of the 30 plus years of medium resolution (30 m) Landsat data to quantify the spatial patterns of change in the extent of water bodies in the Arctic tundra in Nunavut, Canada. Our results show a divergent pattern of change—growing surface water extent in the north-west and shrinking in the south-east—which is not a function of the overall distribution of surface water in the region. The observed changes cannot be explained by latitudinal stratification, nor is it explained by available temperature and precipitation records. However, the sign of change appears to be consistent within the boundaries of individual watersheds defined by the Canada National Hydro Network based on the random forest analysis. Using land cover maps as a proxy for ecological function we were able to link shrinking tundra water bodies to substrates with shallow soil layers (i.e. bedrock and barren landscapes) with a moderate correlation ( R ^2 = 0.46, p < 0.001). It has previously been reported that rising temperatures are driving a deepening of the active layer and shrinking water bodies can be associated with coarse textured soils beneath the lakes. Unlike water bodies with soil, or gravel, beneath them the water bodies that are situated on bedrock are likely cut off from ground water. Drying water bodies clustered in areas of bedrock and thin soils points to evaporation as an important driver of surface water decrease in these cases.
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