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 km(3) 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).

Automated summary

The Strait of Belle Isle is a crucial pathway for water exchange between the Labrador Shelf and the Gulf of St. Lawrence. The study analyzes the seasonal and inter-annual variability of transport in the strait, finding that tidal currents are consistent and transports are highest from September to January. The computed volumes of Labrador Shelf water entering the Gulf of St. Lawrence are consistent with previous models, suggesting that the flow through the strait accounts for a significant proportion of the winter surface mixed layer in the Gulf of St. Lawrence.