Fig. 4.

Changes in DOC concentration (micromoles per kilogram). DOC (34) in the core of the North Atlantic Deep Water along Atlantic transect A16 (*) and in the Circumpolar Deep Water along Pacific transect P16 $\left(\mathrm{•}\right)$. Water samples were used from the neutral density surfaces consistent with these water masses: $41.25<{\sigma }_{3000}<41.5$ in the Atlantic and $45.85<{\sigma }_{4000}$ in the Pacific (34). The running mean across ${15}^{\circ }$ N-S (solid line) is superimposed on the individual DOC measurements (single points). The 1- to 2-μM increase in DOC at the equator relative to the background trend in both basins is consistent with increased particle export from enhanced primary production at the equator. Data from cdiac.esd.ornl.gov/oceans/RepeatSections/.