Diagnosing overturning and water mass transformation in the Labrador Sea from Argo and PALACE floats

We use Argo and PALACE floats, which have been sampling the Labrador Sea since the mid 1990s, to examine the Labrador Sea overturning and its variability on seasonal and decadal timescales. Floats have collected observations in all seasons as well as in the boundary current, allowing for an examination of the seasonal signal of the overturning and of the boundary current’s contribution to the overturning. We construct seasonal composite geostrophic velocity sections across the mouth of the Labrador Sea from potential density profiles and float trajectories at 1000 m. The velocity sections are used to calculate the horizontal and overturning circulations and the water mass transformation. We also track the seasonal and spatial patterns of properties in the boundary current to evaluate theoretical estimates of sinking in the boundary current. The recent Argo observations, collected during a period of relatively weak deep convection, are compared to PALACE float observations from the mid-1990s, a period of stronger deep convection.