Hudson Strait Inflow: Structure and variability

Hudson Strait is the main pathway of heat, mass, and freshwater exchange between Hudson Bay, the Arctic, and the North Atlantic. Flow along the southern coast, a low saline, baroclinic jet directed towards the North Atlantic, has received more attention due to its potential impact on deep convection in the Labrador Sea. However, details about the westward, barotropic flow along the northern coast of Hudson Strait remain unknown due to the lack of observations. It is thought that the inflow is comprised of waters from Baffin Bay, via the Baffin Island Current, as well as waters from the Labrador Sea. Hudson Strait inflow waters affect the physical and biogeochemical systems of the bay, as well as the marine ecosystem, which supports the livelihoods of many indigenous communities surrounding the Hudson Bay Complex. Additionally, knowing the properties of the inflowing waters will help our understanding of water mass transformations occurring in the bay due to sea ice growth and melt, continental runoff, as well as tidal mixing. We present data from two synoptic surveys of the properties and geostrophic flow across Hudson Strait from 2008 and 2009, as well as data from four moorings deployed in the strait from 2008-2009. Three moorings were deployed on the northern side of the strait to map the inflow, and one was deployed on the southern side of the strait to map the outflow. Mooring data show two separate regimes in the strait. Along the southern side, a stratified, fresh outflow is present (consistent with earlier studies), with the strongest flow in the winter coinciding with the previous year’s spring freshet. Variability in the outflow velocities occurs mainly at the surface. Along the northern coast, we present the first year round measurements of the Hudson Strait inflow. The inflow is a weakly stratified, saline flow, with a less pronounced seasonal cycle. Shear is small along the northern coast, with seasonality in the inflow being present throughout the water column.