Health & Environmental Research Online (HERO)


Print Feedback Export to File
3031025 
Journal Article 
POC fluxes estimated from Th-234 in late spring-early summer in the western subarctic North Pacific 
Kawakami, H; Honda, MC; Matsumoto, K; Wakita, M; Kitamura, M; Fujiki, T; Watanabe, S 
2015 
Yes 
Journal of Oceanography
ISSN: 0916-8370 
71 
3 
311-324 
WOS:000355181400008 
Measurements of Th-234, particulate organic carbon (POC), nutrients and net primary production were made at station K2 (47A degrees N, 160A degrees E) in the western subarctic North Pacific Ocean six times from 3 June to 17 July 2006. Net primary productions varied from 263 to 732 mgC m(-2) d(-1). Th-234 was used as a tracer to estimate POC fluxes from the surface layer to 100 m depth. POC fluxes varied from 14 to 284 mgC m(-2) d(-1). The maximum POC flux and net primary production in this study were much higher than those observed previously at station K2 (179 mgC m(-2) d(-1) in July 2003 for POC flux, 552 mgC m(-2) d(-1) in May 2004 for net primary production). Because maximum chlorophyll a in this study (1.3 A mu g L-1) was also much higher than previous values at station K2 (1.0 A mu g L-1 in August 2004), we assumed that high-frequency observations had allowed measurement of a near annual peak of biological production and biological pump activity. The net primary productions and POC fluxes changed greatly during the study period. Biological production and export in this region varied greatly during this season. The export ratio (POC flux/net primary production) in this season (23 +/- A 1 %) was less than the annual export ratio in this region (29 +/- A 1 % in 2002-2005), although this ratio was higher than those in the other oceans (5-10 %). POC export (5.0 +/- A 0.1 gC m(-2)) in late spring-early summer was about half that of net community production (10.2 +/- A 0.6 gC m(-2)) estimated from the drawdown of phosphate during the study period. We suggest that the pathways of carbon export, other than the sinking of particles, were transport by zooplankton and so on. 
Biological pump; Th-234; POC flux; High-frequency observations; Western subarctic North Pacific