A unique set of physical, bio-optical, and meteorological observations were made from a mooring located in the open ocean south of Iceland (59¿29.5'N, 20¿49.8'W) from April 13 to June 12, 1989. The present measurements are apparently the first to resolve the rapid transition to springtime physical and biological conditions at such a high latitude site. Our data were collected with bio-optical and physical moored systems every few minutes. The abrupt onset of springtime stratification was observed with the mixed layer shoaling from ~550 m to ~50 m in ~5 days. During this period a major phytoplankton bloom occurred with a tenfold increase in near-surface chlorophyll concentration in less than 3 weeks. Our statistical analysis indicates that the velocity shear in the upper layer is driven primarily by local wind stress. Mesoscale variability is also apparent from these and concurrent airborne oceanographic lidar observations. Our complementary modeling results suggest that the near-surface layer may be reasonably well described by a one-dimensional model and that the spring bloom was initiated during incipient near-surface restratification.