Temporal trends in deep ocean Redfield ratios

The Redfield ratio [carbon:nitrogen:phosphorus (C:N:P)] of particle flux to the deep ocean is a key factor in marine biogeochemical cycling. Changes i n oceanic carbon sequestration have been Linked to variations in the Redfie ld ratio on geological time scales, but this ratio generally is assumed to be constant with time in the modern ocean. However, deep-water Redfield rat ios in the northern hemisphere show evidence for temporal trends over the p ast five decades. The North Atlantic Ocean exhibits a rising N:P ratio, whi ch may be related to increased deposition of atmospheric nitrous oxides fro m anthropogenic N emissions. In the North Pacific Ocean, increasing C:N and C:P ratios are accompanied by rising remineralization rates, which suggest s intensified export production. Stronger export of carbon in this region m ay be due to enhanced bioavailability of aeolian iron. These findings imply that the biological part of the marine carbon cycle currently is not in st eady state.