Production enhancement by artificial upwelling: a simulation study

A coupled physical-chemical-biological ocean model was applied to study primary production in an idealized 60-km long and 4-km wide fjord. Three different scenarios were simulated: (a) Without fresh water runoff; (b) A river at the head of the fjord adds 100 m(3) s(-1) fresh water to the surface layer; (c) The river adds 90 m(3) s(-1) fresh water to the surface layer and 10 m(3) s(-1) enters the fjord through a pipe at 50 m depth. The average productions in the inner 40 km of the fjord for the three scenarios are 68, 70 and 233 g C m(-2) year(-1) respectively. It is thus shown that there is a considerable potential for increasing the primary production in many fjords and coastal areas by submerging some of the river runoff. Because of the higher silicate content of the deeper water, artificial upwelling tends to stimulate diatom more than flagellate growth. This may be beneficial to mariculture developments. The sensitivity of the simulated primary production to horizontal and vertical resolution, horizontal viscosity, vertical diffusivity and viscosity, discharge depth, wind forcing, sill depth and pulsating the discharge is also studied. A simulation where a large river flux (90 m(3) s(-1)) was submerged, showed that primary production was significantly enhanced in the outer parts of the fjord as well as along the coastline.