Climatology of Transport in the Strait of Belle Isle

The Strait of Belle Isle (SBI) is an important pathway for water mass exchanges between the Labrador Shelf and the Gulf of St. Lawrence (GSL), particularly for transport toward the GSL. Seasonal and inter‐annual variability of transport in the SBI are examined using 15 years of moored acoustic Doppler current profiler data. Tidal currents are largely along strait and homogeneous with depth. Transports are toward the GSL on average, lowest (−1.0 ± 0.8 dSv) from April to July, and highest (−4.0 ± 1.1 dSv) from September to January. Averaged seasonal transports are usually within one standard deviation of previously published modeled values. The volume of winter Labrador Shelf water (LShW) entering the GSL is computed by transport integration and compares well with integrated volumes that meet LShW temperature‐salinity criteria during an annual March survey of the GSL. Integrating over the whole year showed that on average 649 ± 397 km3 enters the GSL after the March surveys are conducted, independently of the volume that has entered up to March; this addition represents on average about a third of the total volume. Annual volumes of LShW calculated from transport suggest that flow through the SBI accounts for 12%–18% of the GSL winter surface mixed layer. Cross‐strait current shear may affect transport integration values, but sea surface temperature data suggests this bias is limited to the summer. Corrections are empirically derived to account for cross‐strait shear in our transport calculation. The corrected time series suggests that the average transport may be flowing toward the Labrador Shelf in July (0.6 ± 1.0 CI [0.1 1.1] dSv). Plain Language Summary The Strait of Belle Isle (SBI) is the waterway at the northeastern end of the Gulf of St. Lawrence (GSL) that connects it to the Labrador Shelf, and where water may move in both directions. Despite its importance, there are not many recent measurements of water movement across this strait. This is because the SBI is remote from most routine oceanographic operations, and strong currents, sea ice, and icebergs complicate mooring design and restrict study site selection. Our study presents 15 years of new measurements obtained using contemporary technologies allowing for a better assessment of the contribution of Labrador Shelf waters to the GSL. In the future, they may also contribute to improving ocean models of the Northwest Atlantic. Key Points A 15‐year Strait of Belle Isle transport time series is calc