西北冰洋表-底层碳动力学耦合作用的同位素(13C,234Th)指示

The coupling of upper ocean-benthic carbon dynamics in the ice-free western Arctic Ocean(the Chukchi Sea and the Canada Basin) was evaluated during the late July–early September 2003 using natural stable(13C) and radioactive(238U-234Th) isotope tracers. POC export flux estimated from 234Th/238 U disequilibria and dissolved CO2 concentration([CO2(aq)]) pointed out that the strengthened biological pump in the Chukchi Shelf have significantly lowered [CO2(aq)] and altered the magnitude of isotopic(12C/13C) fractionation during carbon fixation in the surface ocean. Further, d13 C signatures of surface sediments(d13Csed) are positively correlated to those of weighted d13 CPOC in upper ocean(d13Csed =13.64+1.56×d13CPOC, r2=0.73, p0.01), suggesting that the POC isotopic signals from upper ocean have been recorded in the sediments, partly due to the rapid export of particles as evidenced by low residence times of the highly particle-reactive 234 Th from the upper water column. It is suggested that there probably exists an upper ocean-benthic coupling of carbon dynamics, which likely assures the sedimentary d13 C record an indicator of paleo-CO2 in the western Arctic Ocean.

Insights into the coupling of upper ocean-benthic carbon dynamics in the western Arctic Ocean from an isotopic (13C, 234Th) perspective

The coupling of upper ocean-benthic carbon dynamics in the ice-free western Arctic Ocean (the Chukchi Sea and the Canada Basin) was evaluated during the late July-early September 2003 using natural stable (13C) and radioactive (238U-₂₃₄Th) isotope tracers. POC export flux estimated from ₂₃₄Th/238U disequilibria and dissolved CO₂ concentration ([CO₂(aq)]) pointed out that the strengthened biological pump in the Chukchi Shelf have significantly lowered [CO₂(aq)] and altered the magnitude of isotopic (12C/13C) fractionation during carbon fixation in the surface ocean. Further, δ13C signatures of surface sediments (δ13C_sed) are positively correlated to those of weighted δ13CPOC in upper ocean (δ13C_sed =13.64+1.56×δ13CPOC, r2=0.73, p<0.01), suggesting that the POC isotopic signals from upper ocean have been recorded in the sediments, partly due to the rapid export of particles as evidenced by low residence times of the highly particle-reactive ₂₃₄Th from the upper water column. It is suggested that there probably exists an upper ocean-benthic coupling of carbon dynamics, which likely assures the sedimentary δ13C record an indicator of paleo-CO₂ in the western Arctic Ocean.