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Seasonal and interannual changes in particulate organic carbon export and deposition in the Chukchi Sea

2007; American Geophysical Union; Volume: 112; Issue: C10 Linguagem: Inglês

10.1029/2006jc003555

2156-2202

Kate Lepore, S. Bradley Moran, Jacqueline M. Grebmeier, Lee W. Cooper, Catherine Lalande, Wieslaw Maslowski, Victoria Hill, Nicholas R. Bates, Dennis A. Hansell, Jeremy T. Mathis, Roger Kelly,

Methane Hydrates and Related Phenomena

Particulate organic carbon (POC) export fluxes were estimated in the shelf‐slope region of the Chukchi Sea using measurements of 234 Th −238 U disequilibria and the POC/ 234 Th ratio in large (>53‐ μ m) particles. These export fluxes were used in conjunction with rates of primary productivity and benthic carbon respiration to construct a POC budget for this shelf‐slope region. Samples were collected along a series of shelf‐basin transects in the spring (May–June) and summer (July–August) of 2004. These stations were previously occupied during the ice covered (spring) and open water (summer) seasons of 2002, allowing for an interannual comparison of export flux. In contrast to 2002, when open water POC fluxes were significantly higher than in the ice‐covered period, POC export fluxes in 2004 were similar during the spring (average = 19.7 ± 24.8 mmol C m −2 d −1 ) and summer (average = 20.0 ± 14.5 mmol C m −2 d −1 ). The high POC fluxes measured during the spring are attributed to a plankton bloom, as evidenced by exceptionally high rates of primary productivity (average = 124.4 ± 88.1 mmol C m −2 d −1 ). The shelf‐slope budget of particulate organic carbon indicates that 10–20% of primary productivity was exported below 50 m but was not consumed during benthic carbon respiration or burial and oxidation in underlying sediments. Furthermore, a water column−sediment budget of 234 Th indicates that particulate material is retained in shelf sediments on a seasonal basis.