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Variations In Surface Export Fluxes Of POC During Ice-melting In The Arctic Ocean

Posted on:2018-10-19Degree:DoctorType:Dissertation
Country:ChinaCandidate:J H HeFull Text:PDF
GTID:1360330518484515Subject:Marine Chemistry
Abstract/Summary:PDF Full Text Request
Export fluxes of particulate organic carbon(POC)were derived from 210Po/210Pb disequilibrium method and 234Th/238U disequilibrium method during the 4Th and 5Th Chinese National Arctic Research Expedition(CHINARE-4,July 1?September 28,2010,and CHIN ARE-5),respectively.In 2010,the average residence time of particulate 210Po were in the range of-14.92 a?1.52 a,which is higher than that of dissolved 210Po,-7.17 a?-0.70 a.Distinctive dissolved 210Po excesses were observed at all stations,with an average 210Po/210Pb)A.R.of 1.91 0.20.The average POC export fluxes from the euphotic zone were calculated according to two different hypotheses(E method and B method)with irreversible scavenging model,and represented a decreasing trend from low latitude to high latitude.The repeated sampling stations demonstrated negati-ve POC fluxes,-834 mmol C/m2/a and-44 mmol C/m2/a in E method,-1097 mmol C/m2/a and-33 mmol C/m2/a in B method,is much lower than that of first sampling time,945 mmol C/m2/a and 651 mmol C/m2/a in E method,1848 mmol C/m2/a and 1051 mmol C/m2/a in B method,which meant that the capacity of CO2 absorption after ice melting declined inlate summer,or POC input via lateral transport of particulate matter from nearby waters.The POC export fluxes showed an decreasing trendtoward higher latitude,meant the higher biological pump in the Chukchi sea than that in the Canada Basin.During the CHINARE-5 period,the residence time of particulate 234Th were from-358 d to 1956 d,higher than that of dissolved 234Th-5.54 d?400 d.The highest value of POC flux 100.49 mmol/m2/d appeared at station SR03,and the lowest value 0.17 mmol/m2/d occurred at station SR01.The POC export fluxes derived from 234Th/238U method also represented a decreasing trend from low latitude to high latitude,and the average value of POC export fluxes in R1-R5,51.12 mmol/m2/d(E method)and 47.32 mmol/m2/d(B method),were high than that of SR01?SR05,29.52 mmol/m2/d(E method)and 43.19 mmol/m2/d(B method).This decreasing trend is consistent with the results derived from 2'0Po/2'0Pb disquilibrium method.The above results show that high biological pump exist in the Arctic Ocean during the summer season,although there was a decreasing trend in the late summer and during the past two decades.The Arctic Ocean is a potential C02 sink in future and also the capability of Canada basin is higher than other area due to the longer ice cover time at present.
Keywords/Search Tags:210Po/210Pb disequilibrium, 234Th/238U disequilibrium, Particulate organic carbon, Ice-melting period, the Arctic Ocean
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