Phytoplankton phenology and production around Iceland and Faroes

Phytoplankton phenology and primary production were examined in the Iceland–Faroe region through synthesis of all available data, both in situ and remotely sensed. In the Arctic water, the early onset of stratification in spring gave rise to the rapid shallowing of the mixed layer and triggered the earlier spring bloom north of Iceland, whereas the weakly stratified water-column in the Atlantic water and associated deep mixed layer delayed the spring bloom south of Iceland. The protocol (Nearest Neighbor Method, NNM) developed by Platt et al. (2008) was used to estimate the daily, water-column primary production from ocean color data. The key element of the procedure is an archived database, including (in this implementation) 505 sets of parameters of photosynthetic–light curves and 197 vertical profiles of chlorophyll around Iceland–Faroe region. The spatial structure in the climatology of annual primary production determined in this way was consistent with observations made by the simulated in situ method using ships as a platform, but, inevitably, the fields produced from the remotely sensed data were smoother. The annual primary production estimated by the NNM method overestimates the (much more sparse) data for in situ production by 50% on average. We examined the relative errors in the estimation of primary production that would arise from ignorance of the non-uniformity in the biomass profile. The vertically uniform model tended to underestimate the annual primary production by about 36% compared with the non-uniform model in a spectral calculation.