the one project that actually measures oceanic currents directly (and continuously) is the RAPID MOC project. To my knowledge, there is not a similar project for the Labrador current.

The article describes a coral growth ring study, meaning a proxy study, which may imply that not a single current measurement was taken. Perhaps a few were taken (snapshots over the years). As I tried to explain in Frank's diary, taking snapshot measurements from ocean currents is a method riddled with statistical uncertainties and wouldn't give a proper picture.