Dissolved Organic Radiocarbon in the Central Pacific Ocean

• Published in: Geophysical Research Letters
• Main Authors: Druffel, Ellen R. M., Griffin, Sheila, Wang, Ning, Garcia, Noreen G., McNichol, Ann P., Key, Robert M., Walker, Brett D.
• Format: Report
• Language: English
• Published: AMER GEOPHYSICAL UNION 2019
• Subjects: Geology; Geosciences; Multidisciplinary; TEMPORAL VARIABILITY; CARBON; SAMPLES; MATTER; EXTRACTION; Antarctic; Pacific; Antarc*; Alaska
• Online Access: http://ir.gig.ac.cn/handle/344008/50098; https://doi.org/10.1029/2019GL083149

We report marine dissolved organic carbon (DOC) concentrations, and DOC Delta C-14 and delta C-13 values in seawater collected from the central Pacific. Surface Delta C-14 values are low in equatorial and polar regions where upwelling occurs and high in subtropical regions dominated by downwelling. A core feature of these data is that 14 C aging of DOC (682 +/- 86 14 C years) and dissolved inorganic carbon (643 +/- 40 C-14 years) in Antarctic Bottom Water between 54.0 degrees S and 53.5 degrees N are similar. These estimates of aging are minimum values due to mixing with deep waters. We also observe minimum Delta C-14 values (-550%0 to - 570%0) between the depths of 2,000 and 3,500 m in the North Pacific, though the source of the low values cannot be determined at this time. Plain Language Summary Most of the organic carbon in ocean water is in the dissolved form, like the broth in chicken soup. Even though it is believed that dissolved organic carbon (DOC) is formed during photosynthesis in the surface ocean using modern carbon, its radiocarbon age is surprisingly thousands of years old. We present the first transect of radiocarbon in DOC for the Pacific Ocean. We find that the radiocarbon age of DOC in the bottom waters decreases similarly to that found in the more abundant dissolved inorganic carbon. We conclude that DOC ages in the bottom water as it flows northward toward Alaska.