The Deep Western Boundary Current in the Labrador Sea From Observations and a High-Resolution Model

Long-term observations from a 17 year long mooring array at the exit of the Labrador Sea at 53 degrees N are compared to the output of a high-resolution model (VIKING20). Both are analyzed to define robust integral properties on basin and regional scale, which can be determined and evaluated equally well. While both, the observations and the model, show a narrow DWBC cyclonically engulfing the Labrador Sea, the model's boundary current system is more barotropic than in the observations and spectral analysis indicates stronger monthly to interannual transport variability. Compared to the model, the observations show a stronger density gradient, hence a stronger baroclinicity, from center to boundary. Despite this, the observed temporal evolution of the temperature in the central Labrador Sea is reproduced. The model results yield a mean export of North Atlantic Deep Water (NADW) (33.05.7 Sv), which is comparable to the observed transport (31.25.5 Sv) at 53 degrees N. The results also include a comparable spatial pattern and March mixed layer depth in the central Labrador Sea (maximum depth approximate to 2,000 m). During periods containing enhanced deep convection (1990s) our analyses show increased correlation between LSW and LNADW model transport at 53 degrees N. Our results indicate that the transport variability in LSW and LNADW at 53 degrees N is a result of a complex modulation of wind stress and buoyancy forcing on regional and basin wide scale.