Estimation And Determination Of Carbon Fluxes On Three Interfaces Of Western Arctic Ocean In Summertime

The carbon cycling in Arctic Ocean is one of the essential problems in global climate change research, the key processes of which include air-sea CO₂ exchange, particulate organic carbon export from euphotic zone and organic carbon sedimentation. Quantitative determination and estimation of the carbon absorbing, transferring and burial rate in the processes above have important significances.In this study, the air-sea CO₂ exchange fluxes were estimated from CO₂ partial pressure in the atmosphere and surface seawater, the euphotic zone POC export fluxes were derived with (234)^Th/238U disequilibrium in the upper water column and the organic carbon burial rate was measured from 210Pb specific activity vertical distribution in the sediment. By determining these parameters and analyze the relationship between them, evaluations of carbon cycling efficiency and carbon sink capacity of Arctic Ocean were made, to enhance the understanding of the status and feedback of Arctic Ocean under the background of global climate change.The air-sea difference of CO₂ partial pressure ranged from -256.3 to 10.7μatm, with an average of -92.9±60.6μatm, which was mainly controlled by physical factors in basin region while by biological pump in Chukchi shelf or southern Canada Basin. With the seaice coverage correction, air-sea CO₂ exchange fluxes showed variation from -24.8 to 1.0 mmol C/m²/d, with an average of -7.0±6.7 mmol C/m²/d.The average of specific activity ratios of (234)^Th and 238U was 0.86±0.34. (234)^Th deficit to 238U were widely found in the shelf area, but excess of (234)^Th were observed in frozen ice zone in Canada Basin due to the release of particles during the sea ice melting. The POC export fluxes from euphotic zone ranged from 1.8 to 79.2 mmol C/m²/d (on average of 24.9±23.3 mmol C/m²/d). High ThE ratio of 21 % was estimated, revealing an efficient biological pump in study region.The sedimentation rate in the north Chukchi Shelf was 0.6 mm/a, the apparent mass sediment accumulation rate was 0.72 kg/m²/a, and the organic carbon burial rate was 517 mmol C/m²/a.Basically all the CO₂ exchanged into surface ocean via air-sea interface was fixed and transferred to deeper water, of which 29 % was buried in the sediment permanently. The ratio of the carbon fluxes on the three interfaces was 1:2:0.6.The short term, mid-long term and ultimate carbon sink capacity of Chukchi Sea were 10.0±3.4 T g C, 11.6±9.0 T g C and 3.4 T g C/a, occupying 0.5±0.2⁰.7±0.2 %, 0.3 % and 2.1 % of the total marine carbon sink capacity, the total marine export productivity and the total marine ultimate carbon sink capacity.