Fluxes of carbon and nutrients to the Iceland Sea surface layer and inferred primary productivity and stoichiometry

摘要

This study evaluates long-term mean fluxes of carbon and nutrients to theupper 100 m of the Iceland Sea. The study utilises hydro-chemical data fromthe Iceland Sea time series station (68.00° N, 12.67° W),for the years between 1993 and 2006. By comparing data of dissolved inorganiccarbon (DIC) and nutrients in the surface layer (upper 100 m), and asub-surface layer (100–200 m), we calculate monthly deficits in thesurface, and use these to deduce the long-term mean surface layer fluxes thataffect the deficits: vertical mixing, horizontal advection, air–sea exchange,and biological activity. The deficits show a clear seasonality with a minimumin winter, when the mixed layer is at the deepest, and a maximum in earlyautumn, when biological uptake has removed much of the nutrients. The annualvertical fluxes of DIC and nitrate amounts to 2.9 ± 0.5 and0.45 ± 0.09 mol m?2 yr?1, respectively, and the annualair–sea uptake of atmospheric CO₂ is4.4 ± 1.1 mol C m?2 yr?1. The biologically drivenchanges in DIC during the year relates to net community production (NCP), andthe net annual NCP corresponds to export production, and is here calculatedas 7.3 ± 1.0 mol C m?2 yr?1. The typical, medianC : N ratio during the period of net community uptake is 9.0, and clearlyhigher than the Redfield ratio, but is varying during the season.