C-14 ACTIVITY OF DISSOLVED ORGANIC-CARBON FRACTIONS IN THE NORTH-CENTRAL PACIFIC AND SARGASSO SEA

Article

关键词: RADIOCARBON;    MATTER;    OCEAN;   

DOI  :  10.1038/357667a0

来源: SCIE

【 摘 要 】

RADIOCARBON measurements of dissolved organic carbon (DOC) oxidizable by ultraviolet irradiation (DOC(uv)) yielded apparent ages of approximately 6,000 yr in the deep waters of the oligotrophic north-central Pacific gyre 1. Recent reports of a potentially larger pool of DOC as measured by high-temperature catalytic combustion (DOC(htc)) using discrete injections of sea water 2,3 have led to speculation that 'younger', more recently produced DOC could contribute significantly to overall oceanic organic carbon fluxes, owing to its suspected greater biological lability 4-6. Here we present a comparison of DELTA-C-14 (the deviation in parts per thousand from the C-14 activity of nineteenth-century wood) 7 of the DOC(htc), DOC(uv), and humic substances in profiles from the oligotrophic north-central Pacific and Sargasso Sea. For each ocean, the DELTA-C-14 values of all three fractions are remarkably similar, yielding no evidence for a component of DOC that is cycled through the system on timescales shorter than several thousands of years. We observe an age difference between the two oceans of approximately 2,000 yr for the deepest DOC, which can largely be accounted for by differences in the DELTA-C-14 of the DOC sources to the deep basins, and by the different deep-water circulation patterns and transit times in the two oceans.

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