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Abstract

Assessing spatiotemporal water storage variability in the Great Lakes watershed (GLW) is critical for water resources in the US and Canada. Here, we assess terrestrial water storage (TWS) variations in the GLW by using data from global positioning system (GPS), GRACE satellites and a composite hydrological model (CHM), and examine the relationship between TWS and climate changes, such as ENSO, NAO etc. Observations show a surface water storage increase of ~175 km³ from 2010 to 2020, however, Earth's crust subsidence caused by this water increase alone cannot explain the GPS recorded vertical displacement, suggesting additional contributions need to be explored.The spatial pattern in annual change of GPS-inverted TWS agrees well with that from the CHM, indicating that the annual cycle mainly dominated by soil moisture and snow. GRACE underestimates the spatial patterns of long-term and seasonal TWS fluctuations w.r.t GPS. The peak in GPS-inverted TWS occurs in March, coinciding with those from GPS, however, one to two months ahead of that appear in the CHM. The magnitude of seasonal groundwater oscillation is ~60 km³ with peaking in September, coinciding with the Great Lakes surface water peak; however, the magnitudes and phases of groundwater storage vary markedly among the sub-regions in the GLW. ENSO and NAO have impacts on GLW TWS variations at interannual scale through effecting the regional precipitation and temperature. The high-density GPS stations in the GLW represent an independent tool to estimate high-resolution TWS changes and provide critical insights for understanding water storage variations.