The Influence of James Bay River Discharge on Churchill, Manitoba Sea Level

Abstract

The Hudson Bay region faces the possible impact of two anthropogenic modifications, hydro-electric damming and climate change. Both of these have the potential to influence sea level in Hudson and James Bay waters. To gain a better understanding of the interplay between sea level and runoff into this water system, the impact of James Bay spring runoff on sea level variation at Churchill, Manitoba, is assessed. James Bay discharge data for 1963 to 1983 are used with corresponding sea level data recorded at Churchill. A significant correlation between spring (May and June) discharge from James Bay and a secondary peak in sea level in October and November at Churchill was found. The coefficient of determination (R2) increased substantially from 26% to 47% when an outlier year, 1963, was removed from the analysis. This is justified due to the limited data available for approximating discharge for that year. A lower limit of 5 cm/s advection speed is estimated for propagation of discharge from James Bay to Churchill consistent with previous estimates. Using the difference in sea level arising from high and low discharge years, it was estimated that 35-50% of the discharge from James Bay does not exit directly from Hudson Bay but recirculates in western Hudson Bay. It can be extrapolated that hydroelectric regulation of the rivers draining into James Bay will potentially affect the seasonal variation of sea level throughout Hudson Bay.