Final answer:
Gravity is lower at Hudson's Bay, Canada, due to isostatic adjustments from the melting of the Laurentide Ice Sheet which previously depressed the Earth's crust in that area.
Step-by-step explanation:
The phenomenon gravity is not uniform over the Earth's surface due to factors such as the Earth's rotation, the position of mountains, ocean trenches and variations in subsurface densities. A notable region where gravity is measurably lower is Hudson's Bay, Canada. This variation is attributed to the Laurentide Ice Sheet that once covered much of North America, including Hudson's Bay. The immense weight of the ice sheet depressed the Earth's crust.
When the ice sheet melted the crust began to rise (isostatic rebound), but has not yet fully recovered and this rebounding process has both reduced the mass and increased the surface elevation in the area leading to a slightly lower gravity field. Differences in gravity can be measured using very sensitive instruments, and these variations are often encapsulated in scientific models of the Earth's gravity field such as the World Geodetic System or the Geoid. It is these more subtle differences that yield the answer to is gravity higher or lower at Hudson's Bay?