Fig. 7. Annual cycle of mixed-later depth irradiance levels (I_MLD) in the Labrador Sea (partitioned into shelves and central basin): vertical bars = climatology, points = average values from LSMP spring and summer missions (vertical lines = standard errors, SE). Solid line = light-limitation threshold parameter (I_t). I_t levels in winter and spring were statistically indistinguishable but statistically different from summer (p <0.01) and autumn (p <0.10) levels.