Document Type

Article

Department/Program

Virginia Institute of Marine Science

Publication Date

1996

Journal

JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS

Volume

101

First Page

20543

Last Page

20552

Abstract

We present Delta(14)C measurements of particulate organic carbon (POC) collected on four cruises at our time series site (station M) in the northeast Pacific Ocean. We observe a large gradient with depth in the suspended POC Delta(14)C values (124-160 parts per thousand). These profiles display lower Delta(14)C values (by 20-30 parts per thousand) in samples between 2500 m and the bottom during June 1992 and July 1993 than those during February and October 1992. Values of Delta(14)C in sinking POC from deep-moored sediment trap collections suggest a semiannual trend that displays lower overall Delta(14)C in material collected during periods of high flux. A limited number of Delta(14)C measurements of small swimmers picked from the trap 650 m above bottom are similar to surface Delta(14)C measurements of dissolved inorganic carbon (DIG) and suspended POC, indicating a surface carbon source. Overall, we postulate that the major process causing lower Delta(14)C values of deep suspended and sinking POC is sorption (or biological incorporation) of ''old'' DOC onto particulate matter. There appears to be a higher ratio of DOC sorbed to sinking particulate matter at times of high flux (late spring and early fall) that can be thought of as a ''stripping out'' of DOC from the water column. The DIC Delta(14)C display a small seasonal variation in the surface waters and is not the sole source of the observed seasonality in the POC Delta(14)C signals.

DOI

10.1029/96JC01850

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