Radiocarbon in dissolved organic carbon of the South Pacific Ocean

Marine dissolved organic carbon (DOC) originates mainly from primary production using dissolved inorganic carbon (DIC) that has young C-14 ages. Paradoxically, the C-14 age of deep DOC ranges from 4000 to 6400 C-14 years, indicating that a portion of DOC survives multiple, deep ocean mixing cycles. Here we show that C-14 ages of DOC from the deep South Pacific are equal to those from the deep north central Pacific. This is contrary to DIC C-14 ages that increase from south to north in the deep Pacific. We hypothesize that DOC in the South Pacific is influenced by input of ancient DOC from hydrothermal flanks and ridges of the East Pacific Rise. We show that DOC C-14 values in the deep Pacific are not controlled by aging during northward transport of deep waters, indicating that the deep oceanic carbon cycle needs reassessment.