Modulation of linear and nonlinear hydroclimatic dynamics by mountain glaciers in Canada and Norway: Results from information-theoretic polynomial selection

Historical streamflow and climate datasets were analyzed for low- and high-frequency hydroclimatic variability. Four glacial/non-glacial catchment pairs were considered, two from the southern Canadian Rocky Mountains and two from arctic coastal Norway. Analyses were performed using daily data, providing high seasonal resolution and facilitating the identification of possible nonlinear hydroclimatic processes. Spearman rank correlation, and an information theory-based polynomial selection method, were employed in parallel. The latter permits straightforward identification of highly nonlinear relationships, simultaneous consideration of multiple models and estimation of the probability of a given relationship, as distinct from conventional p-values. Highly nonlinear (parabolic) atmospheric teleconnections to the Arctic Oscillation and El Nino-Southern Oscillation were confirmed in Norway and Canada, respectively, and their corresponding hydrologic effects were detected; conversely, little evidence for deviation from linearity was found for long-term monotonic trends. Presence or absence of watershed glacial cover was found to fundamentally alter streamflow responses to climate variability and change. In particular, for ecologically highly relevant late-summer low flows, glaciers induced: (1) stronger negative long-term trends than observed for non-glacial basins, presumably reflecting net mass balance declines seen in nearby glaciers, and (2) parabolic teleconnections, largely absent in non-glacial basins, reflecting parabolic air temperature teleconnections and the presence or absence of glacial ice available for melting.