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Abstract:
Great Slave Lake (GSL), located within the Mackenzie River Basin (MRB) in the Northwest Territories, Canada, is one of the deepest (over 600m) freshwater lakes in the world. Large lakes serve as both an indicator of the impact of climate change on regional hydrological dynamics and as a thermal feedback mechanism that may buffer or exacerbate climate change. In summer 2020, GSL levels reached record highs since gauging began in the 1930s, driven by above-average precipitation across the MRB, especially in the Athabasca and Peace River subbasins, and potentially increased permafrost degradation. Recent studies in this area indicate an overall declining secular trend in terrestrial water storage anomalies (TWSA). The objective of this research is to examine in more detail the TWSA in this region, in order to comprehend the underlying sources for the observed trend. The GRACE/FO level-3 mascon product released by the Jet Propulsion Laboratory was evaluated over two decades (April 2002 to March 2022) and data gaps were filled using automated machine learning to provide a continuous time series. Comparisons with the trends derived from ERA5 total precipitation and streamflow station records indicate that the increasing precipitation feeding GSL is countered by increased surface runoff; despite the positive TWSA observed by GRACE-FO beginning in June 2020, the region is, overall, experiencing a declining trend in terrestrial water storage. Studies such as these provide a more comprehensive understanding of the impact of climate change on the hydrological dynamics of the MRB.
