Can Regulation of Freshwater Runoff in Hudson Bay Affect the Climate of the North Atlantic?

A sequence of phenomena links anthropogenic changes in the timing of freshwater runoff in Hudson Bay to a possible impact on the North Atlantic thermohaline circulation. The chain of events starts with the spreading of estuarine plumes under ice and continues with the effect of lowered salinity on the rate of ice formation, regional effects on the scale of Hudson Bay, the export of freshwater to the Labrador Sea, its impact on deep convection in that area, and the relative importance of such changes to the North Atlantic circulation. At each step we compare anthropogenic effects with other factors and place them within the perspective of natural variability. Our conclusion does not support the contention that freshwater runoff regulation, even of all rivers in the basins of Hudson and James Bays, could have a significant or even a detectable effect on the climate of the North Atlantic.