Department of Earth System Science

We present radiocarbon measurements of dissolved inorganic carbon (DIC) in depth profiles from reoccupations of our central North Pacific Ocean and Sargasso Sea (SS) sites. From 1985 to 1999, an increase in Δ¹⁴C values of 6–17‰ was measured between 1150 and 2400 m depth in the North Central Pacific. Natural changes in deep circulation are likely responsible for variability of Δ¹⁴C signatures in the deep ocean, though we cannot rule out the presence of bomb ¹⁴C at this depth range. Bomb ¹⁴C had increased in the deep SS from 1989 to 2000; this is the result of southward transport of North Atlantic Deep Water (NADW) to this site.