AbstractsChemistry

The overall goal of this study was to examine the hydrological and geochemical linkages between the contributing landscape and small tundra lakes affected by shoreline retrogressive thaw slumping (SRTS) in the upland region north east of Inuvik, NT. In 2007, 2008, and 2009, detailed hydroclimatological and geochemical data were obtained from a pair of representative tundra lake catchments (Lake 5A: Control; Lake 5B: Affected by SRTS). This was supplemented with less detailed data obtained from 10 regional small tundra lake catchments (control and affected by SRTS). The hydrology and geochemistry of Lake 5A and Lake 5B exhibited strong seasonal variability that was characterized by spring snowmelt. For the three study years, Lake Level (LL) peaked during spring snowmelt, when the addition of melt water from the contributing landscape led to a rapid rise in LL that was enhanced by snow and ice damming the outlet channel. The addition of this relatively dilute runoff water led to a decrease in the concentration of most major ions and nutrients in the study lakes over the spring months. Notably, the concentration of nutrients increased at the beginning of spring snowmelt, due to the mobilization of surficial organic materials by runoff, before decreasing as runoff to the lake became more diluted. Recent changes in key hydroclimatic factors have likely affected the hydrology and geochemistry of the study lakes. The examination of a suite of hydroclimatic indicators, derived from historical climate data, indicated that the annual May 1st snowpack in Tuktoyaktuk has been increasing at a significant rate over the past half century. Furthermore, detailed snow survey data suggested that the capture of snow by SRTS-affected terrain increases the snowmelt contributions to small tundra lakes. An increase in the contribution of snowmelt inputs to the lake water balance could lead to a higher peak LL and more dilution of lake water. In addition to hydro-climatic drivers, the geochemistry of the study lakes was also driven by SRTS. SRTS-affected lakes had significantly higher concentrations of major ions than unaffected study lakes, due to the addition of relatively ion-rich runoff from SRTS-affected terrain during the spring and summer months. The outlet channels draining the SRTS-affected study lakes also had significantly higher concentrations of major ions than that of the unaffected study lakes, due to the addition of relatively ion-rich lake water, which suggests that SRTS-affected lakes could be a source of major ions to downstream lakes. Graduate