Changing Lake Dynamics Indicate a Drier Arctic in Western Greenland

The water balance of the Arctic tundra is shifting as permafrost stability, seasonality, and the ratio of precipitation to evaporation respond to amplified Arctic warming. While in some northern tundra locations there has been a notable increase in the number of water bodies, generally, the tundra landscape has experienced a decline in the number and area of lakes. We analyzed changes in small lake count (<10,000 m(2)), large lake count (>10,000 m(2)), and lake surface area across the periglacial tundra of western Greenland, using historical satellite and aerial imagery and weather data from the late 1960s to present. Overall, we found a decrease in lake count (21%) and surface area (2%) across our study region. Specifically, smaller ponds were particularly prone to change, with decreases of 28% in count and 15% in surface area. Shrinking lakes often became revegetated by both emergent aquatic and terrestrial vegetation, which captures potential successional trajectories following Arctic lake drying. Additionally, while annual precipitation may be increasing, it occurred primarily during the winter months in the form of snow, which may or may not contribute to the overall growing season water budget. Conversely, the peak growing season months of June, July, and August all have experienced significant increases in potential evaporation rates, thus likely creating a water deficit for much of the growing season. These results suggest that a large section of deglaciated Greenland appears likely to become drier in the summer months, which may result in widespread ecological consequences. Plain Language Summary Arctic tundra environments may become drier as the climate continues to warm, due to changes in precipitation and evaporation patterns, and losses of permanent ground ice. In many Arctic systems, lakes are widely distributed and thus can serve as an early indicator of drying conditions. We predicted that our study region of west Greenland would be particularly susceptible to drying due to low levels of precipitation and observed warming trends at a rate of approximately 0.5 degrees C per decade. Using historical and modern satellite and aerial imagery, we observed a decrease in the number of small lakes by 28% and a 15% decrease in the total area of smaller water bodies between 1969 and 2017. Additionally, we found that many of the disappeared lakes from 1969 appeared to have become vegetated. An analysis of historical weather data suggested that water losses to the atmosphere via evaporation have likely increased, especially in the summer months, which may be contributing to observed lake decline. Declining small lake area across our study region and other parts of the Arctic can have landscape-wide effects such as changes to available animal habitat, increases in the risk of fire, and to the prevalence of drought conditions.