Seasonal snow-cover (SSC) substantially alters surface physical properties over the Northern Hemisphere (NH). It modulates processes within the energy and water cycles, thereby influencing climatology, hydrology, geomorphology and ecology. In spring and summer, snowmelt provides an essential resource for humankind. The identification, quantification and explanation of changing spatial and temporal distributions of SSC helps to predict future impacts on natural and human environments, and informs development of mitigation and adaptation strategies. Because SSC is spatially and temporally heterogeneous, meaningful estimation of trends in its distribution and duration is dependent on long records of remotely-sensed imagery. The Rutgers University Global Snow Laboratory and the United States’ National Oceanic and Atmospheric Administration provide the longest such archive (NOAA-Rutgers Snow Archive, NRSA), dating from 1966. However, several studies have raised questions about the credibility of the signs and magnitudes of trends derived from the NRSA, suggesting that they may be artifacts of technological improvements introduced in 1999. This dissertation improves the spatial resolution at which NH SSC extent and duration trends during the NRSA’s longest continuous section (since 1971) are reported, building on previous hemispheric and continental studies. It demonstrates that the magnitudes of area-related trends are sensitive to assumptions adopted when estimating SSC extent from the NRSA, and that these sensitivities vary spatially. The study assesses whether temporal trajectories of SSConset trends imply abrupt changes in 1999, particularly over more complex terrain, and finds no evidence of this. It also explores the broader climatological contexts of these trends, together with estimated departures from mean conditions. Evidence is presented at monthly intervals for causative chains linking advection of mid-tropospheric warming from lower to higher latitudes, consequent inception of climatologically novel airflows, and the incidence of significant SSConset trends of both signs. Earlier onset of snow-dominated conditions is found to be driven by augmented moisture advected from lower latitudes (in eastern Eurasia) or zonally from oceanic sources (in North America) over regional monthly mean 0°C isotherms. Delayed onset is associated with drier or warmer airflows. These findings support the interpretation that the NRSA-based trends are plausible within their spatial and temporal contexts.
Seasonal snow is an essential component of hydrological systems and climate feedbacks, particularly in western North America, providing cool water to downstream river systems and regulating the global climate. Spatial and temporal variability in snow is high in complex terrain such as mountains, and on spatial scales smaller than regional climate model (RCM) grid sizes. This thesis tests the importance of slope, aspect and elevation effects in the Canadian Land Surface Scheme (CLASS) using three years of data from a climate station near Likely, BC, and extrapolated to a digital elevation model (DEM) domain. Results show that, as expected, snow depth and snow water equivalent (SWE) are sensitive to elevation, and this sensitivity is enhanced when combined with slope and aspect angles. Including sub-grid snow variability increases simulated SWE by up to 45% during snowmelt. Finally, this study supports the use of standardised comparison datasets to validate disparities between simulated and observed data.
Northeastern British Columbia (BC) is undergoing steady development for oil and gas extraction, mainly due to subsurface hydraulic fracturing (fracking), which requires significant quantities of water. Thus, it is of vital importance to obtain accurate long-term water balance information in the complex wetlands of northeastern BC to assist regulators to balance multiple priorities in a way that will not compromise the long-term sustainability of water resources, while minimizing ecological impacts. At the initial phase of this study, all fluxes of the Coles Lake water balance were measured for the 2013_2014 hydrological year. The total storage change was negative (-8.3 mm), and 2013_2014 was considered a relatively dry year. This study also quantifies the water balance fluxes within two boreal watersheds, the Coles Lake and Tsea Lake watersheds, through a combination of observational data analysis and numerical modelling using the MIKE SHE hydrological model for 1979_2014. MIKE SHE model calibration was performed manually based on snowmelt, pressure head, and streamflow, using a trial-and-error parameter adjustment procedure. Similar trends were observed for the Coles Lake and Tsea Lake watersheds although average of actual evapotranspiration (AET = 472.9 mm year-1) was higher while overland flow (OL = 26.3 mm year-1) was lower at the Coles Lake watershed compared to the Tsea Lake watershed (AET= 405.5 mm year-1 and OL = 48.5 mm year-1). Sensitivity simulations with the MIKE SHE model whereby the leaf area index was modified uniformly across the Coles Lake watershed to represent fully open, mixed and closed canopies provided further insights on the role of vegetation on the water balance. Simulated AET = 515, 529, and 558 mm year-1 and OL = 59, 46, and 11 mm year-1 for open, mixed, and closed canopies, respectively. Further, the Coles Lake forcing data were applied for the Tsea Lake watershed as a sensitivity test while other parameters remained unchanged. The variability of the vegetation canopies, and land cover including wetland distribution were the main contributors for different hydrological responses in these two watersheds. Baseline information generated by this study will support the assessment of the sustainability of current strategies for freshwater extraction.
Intermontane lakes are often enclosed by complex topography that creates difficulty in resolving the local and regional wind fields. Quesnel Lake, nestled into the western flank of the Cariboo Mountains in central British Columbia, is one such lake. This study examines the wind climatology of Quesnel Lake at three distinct spatial and temporal scales. Firstly, long-term wind data from meteorological stations bordering the Cariboo Mountains exhibit a cycle of calm and active periods throughout the year. Secondly, an environmentto- circulation synoptic climatology is presented that illustrates the large-scale atmospheric patterns that lead to strong wind events at the lake. Finally, the spatial and temporal variability of the near-surface wind field has been examined using an array of shore-based meteorological stations. The response of the wind field to synoptic forcing is found to be driven primarily by the orientation of the regional 800 hPa pressure gradient. iii
Hudson Bay, a vast inland sea in northern Canada, receives the highest average annual freshwater from the Nelson River system among all other contributing rivers. A rapidly changing climate and flow regulation from hydroelectric developments alter Nelson River streamflows timing and magnitude, affecting Hudson Bay’s physical, biological, and biogeochemical state. Despite recent developments and advances in climate datasets, hydrological models, and computational power, modelling the Hudson Bay system remains particularly challenging. Therefore, this dissertation addresses crucial research questions from the Hudson Bay System (BaySys) project by informing how climate change impacts variability and trends of freshwater-marine coupling in Hudson Bay. To that end, I present a comprehensive intercomparison of available climate datasets, their performance, and application within the macroscale Variable Infiltration Capacity (VIC) model, over the Lower Nelson River Basin (LNRB). This work aims to identify the VIC parameters sensitivity and uncertainty in water balance estimations and investigates future warming impacts on soil thermal regimes and hydrology in the LNRB. An intercomparison of six climate datasets and their equally weighted mean reveals generally consistent air temperature climatologies and trends (1981–2010) but with a prominent disagreement in annual precipitation trends with exceptional wetting trends in reanalysis products. VIC simulations forced by these datasets are utilized to examine parameter sensitivity and uncertainties due to input data and model parameters. Findings suggest that infiltration and prescribed soil depth parameters show prevailing seasonal and annual impacts, among other VIC parameters across the LNRB. Further, VIC simulations (1981–2070) reveal historical and possible future climate change impacts on cold regions hydrology and soil thermal conditions across the study domain. Results suggest that, in the projected climate, soil temperature warming induces increasing baseflows as future warming may intensify infiltration processes across the LNRB. This dissertation reports essential findings in the application of state-of-the-art climate data and the VIC model to explore potential changes in hydrology across the LNRB’s permafrost gradient with industrial relevance of future water management, hydroelectric generation, infrastructure development, operations, optimization, and implementation of adaptation measures for current and future developments.
