Sustainability of high Arctic ponds: Importance of hydrologic linkages

Arctic wetland environments are considered to be sensitive to ongoing climate change (Hinzman et al. 2005) but they have received limited attention despite their ecological importance. To date, ponds and lakes are disappearing in Alaska and Siberia because of climate warming (Fitzgerald et al. 2003; Smith et al. 2005). To better understand and quantify the hydrologic processes which are leading to sustainability and/or demise of High Arctic ponds, a hydrological study was conducted during the summer seasons of 2005 and 2006 at Somerset Island, Nunavut (72°43'N, 94°15'W). A water balance framework which quantifies inputs/outputs and water storage was employed on twelve ponds situated in three broad geomorphic areas (glacial terrain, bedrock, coastal area).;Initial snow cover, while varying amongst ponds, was found to be important in controlling the water level patterns for the summer season. Emphasis was placed on examining fluctuating pond water levels during periods of rain and drying episodes. Evaporation loss and ground seepage, coupled with rainfall and lateral water inputs and outputs were found to be critical in determining storage changes between ponds on a seasonal basis. The position of Moraine ponds in the landscape was important in determining their connectivity to nearby hydrological systems such as streams, late-lying snowbanks and wet meadows, that helped to maintain stable water levels. Shallow active layer development and saturated silty soils of transition zones inhibited seepage and subsurface losses and prevented the ponds from drying out. Large end-of-winter snow accumulations on the Bedrock ponds due to the catchment topography ensured large initial water storage and seasonal sustainability. Sandy soils typical of the Coastal and Plateau ponds favored seepage and subsurface losses leading to desiccation of ponds during dry periods. Seasonal variability in climate influenced the sustainability of these ponds. Large end-of-snow accumulations and frequent rain in 2005 ensured high pond water levels. Diminished snow cover, infrequent rain and prolonged warm spells in 2006 resulted in water resource depletion and even desiccation of ponds at the Coastal and Plateau sites. This study described the range of important factors that affect pond sustainability under a changing climate and findings from this study can be applied to other High Arctic ponds situated in polar desert environments.