Radium-226 (226Ra) activities were measured in the surface water samples collected from the Arctic Ocean and the Bering Sea during the First Chinese National Arctic Research Ex-pedition. The results showed that 226Ra ...Radium-226 (226Ra) activities were measured in the surface water samples collected from the Arctic Ocean and the Bering Sea during the First Chinese National Arctic Research Ex-pedition. The results showed that 226Ra concentrations in the surface water ranged from 0.28 to 1.56 Bq/m3 with an average of 0.76 Bq/m3 in the Arctic Ocean, and from 0.25 to 1.26 Bq/m3 with an average of 0.71 Bq/m3 in the Bering Sea. The values were obviously lower than those from open oceans in middle and low latitudes, indicating that the study area may be partly influenced by sea ice meltwater. In the Bering Sea, 226Ra in the surface water decreased northward, probably as a result of the exchange between the 226Ra-deficient sea ice meltwater and the 226Ra-rich Pacific water. In the Arctic Ocean, 226Ra in the surface water increased northward and eastward. This spa-tial distribution of 226Ra reflected the variation of the 226Ra-enriched river component in the water mass of the Arctic Ocean. The vertical profiles of 226Ra in the Canadian Basin showed a concen-tration maximum at 200 m, which could be attributed to the inputs of the Pacific water or/and the bottom shelf water with high 226Ra concentration. This conclusion was consistent with the results from 2H, 18O tracers.展开更多
Measurement of 228Ra activities in the upper 300 m water column was conducted at two stations in the South China Sea using an MnO2-fiber extraction/β-counting technique of 228Ac. Results showed that 228Ra activities ...Measurement of 228Ra activities in the upper 300 m water column was conducted at two stations in the South China Sea using an MnO2-fiber extraction/β-counting technique of 228Ac. Results showed that 228Ra activities ranged from 0.38 to 3.60 Bq·m-3. The vertical profiles of 228Ra at the time-series station favored a steady state assumption. Based on a one-dimensional steady state model, 228Ra-nitrate coupled approach was applied to stations NS97-43, NS99-53 (T1), NS99-53 (T2). New production thus quantified were 4.4, 5.1 and 5.7 mmolC·m-2·d-1, respectively. f ratios in the South China Sea were estimated from the derived new production and the documented primary productivity in the regime, to be 0.12-0.15.展开更多
Measurements of d D and salinity were carried out in the Prydz Bay during two Antarctic cruises, the 13th and the 14th Chinese National Antarctic Research expeditions (CHINARE). Mass balance calculations based on d D ...Measurements of d D and salinity were carried out in the Prydz Bay during two Antarctic cruises, the 13th and the 14th Chinese National Antarctic Research expeditions (CHINARE). Mass balance calculations based on d D and salinity showed that during the 13th CHINARE cruise, per- centages of glacial meltwater and sea ice meltwater in the study region ranged from 0% to 3.82% and from 3.19% to 4.78%, respectively. Meanwhile, the percentages were 1.53%—3.98% and 3.80%—4.52% during the 14th CHINARE cruise. We depicted plots showing the horizontal dis- tributions of glacial meltwater and sea ice meltwater, and found a footprint of Circumpolar Deep Water (CDW), which may suggest a strong upwelling in this regime. We also noticed a butterfly- like image in the plot, which resulted from two adjacent water masses. It is interesting to note that the butterfly-like image deflected anticlockwise with depth. We suggested that the cause of the deflection could be due to Ekman effect. Depth profiles of glacial meltwater within the Prydz Bay were fundamentally uniform, revealing that inflow of glacial meltwater to the basin was a slower process with respect to the vertical mixing in the water column. Nevertheless, percentage of sea ice meltwater decreased steadily with depth, presumably due to the effect of seasonal cycle of sea ice production.展开更多
During the 134 （1996 1997） and the 19th （2002-2003） Chinese National Antarctica Research Expeditions, we collected 60 discrete surface seawater samples along the cruise from the Chanjiang River （Yangtze） estuary...During the 134 （1996 1997） and the 19th （2002-2003） Chinese National Antarctica Research Expeditions, we collected 60 discrete surface seawater samples along the cruise from the Chanjiang River （Yangtze） estuary （30^.59%, 122^.26＇E） through Taiwan Strait, the South China Sea, and the Eastern Indian Ocean to Prydz Bay, Antarctica （69^.10＇S, 74^.30＇E）, and analyzed them for the 226Ra specific activity. The 226Ra specific activity of the Chanjiang River estuary surface water （3.15 Bq/m3） was found to be the highest among all the surface samples because of the desorption of 226Ra from riverine particles. Between Chanjiang River estuary and 40^.S, 226Ra specific activity was found to be relatively uniform with a mean value of 1.07 Bq/m3 （n= 19, SD=0.14）, similar to that of the open ocean. From 40^.S to 65^.S, 226Ra specific activity increased intensively, then decreased moderately further southwards. Near the Antarctic shore, it increased again, to 2.31 Bq/m3. This distribution was controlled by a combination of deep water upwelling, Southern Ocean fronts, water mixing and the continental 226Ra import. In Prydz Bay and the adjacent sea area, the mean 226Ra activity value was 2.26 Bq/m3 （n=31, SD=0.28）, with a relatively higher value outside of the bay and low 226Ra activity value in the center of the bay. This was consistent with the topography and hydrological setting of the bay. In addition, we extended the study area northward to the Arctic, by combining the published Z26Ra dataset for surface water from the Bering Sea to the Japan Sea. We also discuss the 226Ra distribution of high latitude oceanic surface water and its mechanisms.展开更多
基金supported by the First Chinese National Arctic Research Expedi-tion Program.
文摘Radium-226 (226Ra) activities were measured in the surface water samples collected from the Arctic Ocean and the Bering Sea during the First Chinese National Arctic Research Ex-pedition. The results showed that 226Ra concentrations in the surface water ranged from 0.28 to 1.56 Bq/m3 with an average of 0.76 Bq/m3 in the Arctic Ocean, and from 0.25 to 1.26 Bq/m3 with an average of 0.71 Bq/m3 in the Bering Sea. The values were obviously lower than those from open oceans in middle and low latitudes, indicating that the study area may be partly influenced by sea ice meltwater. In the Bering Sea, 226Ra in the surface water decreased northward, probably as a result of the exchange between the 226Ra-deficient sea ice meltwater and the 226Ra-rich Pacific water. In the Arctic Ocean, 226Ra in the surface water increased northward and eastward. This spa-tial distribution of 226Ra reflected the variation of the 226Ra-enriched river component in the water mass of the Arctic Ocean. The vertical profiles of 226Ra in the Canadian Basin showed a concen-tration maximum at 200 m, which could be attributed to the inputs of the Pacific water or/and the bottom shelf water with high 226Ra concentration. This conclusion was consistent with the results from 2H, 18O tracers.
基金This work was supported by Chinese National Research Program of Science and Technology (Grant No. 97-926-04-02) the National Natural Science Foundation of China (Grant No. 49676296).
文摘Measurement of 228Ra activities in the upper 300 m water column was conducted at two stations in the South China Sea using an MnO2-fiber extraction/β-counting technique of 228Ac. Results showed that 228Ra activities ranged from 0.38 to 3.60 Bq·m-3. The vertical profiles of 228Ra at the time-series station favored a steady state assumption. Based on a one-dimensional steady state model, 228Ra-nitrate coupled approach was applied to stations NS97-43, NS99-53 (T1), NS99-53 (T2). New production thus quantified were 4.4, 5.1 and 5.7 mmolC·m-2·d-1, respectively. f ratios in the South China Sea were estimated from the derived new production and the documented primary productivity in the regime, to be 0.12-0.15.
基金This work was supported by the grants to YPH from the National Natural Science Foundation of China(Grant No.49836010)the Chinese National Research Program of Science and Technology(Grant No.98-927-01-05).
文摘Measurements of d D and salinity were carried out in the Prydz Bay during two Antarctic cruises, the 13th and the 14th Chinese National Antarctic Research expeditions (CHINARE). Mass balance calculations based on d D and salinity showed that during the 13th CHINARE cruise, per- centages of glacial meltwater and sea ice meltwater in the study region ranged from 0% to 3.82% and from 3.19% to 4.78%, respectively. Meanwhile, the percentages were 1.53%—3.98% and 3.80%—4.52% during the 14th CHINARE cruise. We depicted plots showing the horizontal dis- tributions of glacial meltwater and sea ice meltwater, and found a footprint of Circumpolar Deep Water (CDW), which may suggest a strong upwelling in this regime. We also noticed a butterfly- like image in the plot, which resulted from two adjacent water masses. It is interesting to note that the butterfly-like image deflected anticlockwise with depth. We suggested that the cause of the deflection could be due to Ekman effect. Depth profiles of glacial meltwater within the Prydz Bay were fundamentally uniform, revealing that inflow of glacial meltwater to the basin was a slower process with respect to the vertical mixing in the water column. Nevertheless, percentage of sea ice meltwater decreased steadily with depth, presumably due to the effect of seasonal cycle of sea ice production.
基金Supported by the National Natural Science Foundation of China(Nos.40706033 and 40806031)COMRA Program(Nos.DYXM-115-02-1-12 and DY115-01-2-5)
文摘During the 134 （1996 1997） and the 19th （2002-2003） Chinese National Antarctica Research Expeditions, we collected 60 discrete surface seawater samples along the cruise from the Chanjiang River （Yangtze） estuary （30^.59%, 122^.26＇E） through Taiwan Strait, the South China Sea, and the Eastern Indian Ocean to Prydz Bay, Antarctica （69^.10＇S, 74^.30＇E）, and analyzed them for the 226Ra specific activity. The 226Ra specific activity of the Chanjiang River estuary surface water （3.15 Bq/m3） was found to be the highest among all the surface samples because of the desorption of 226Ra from riverine particles. Between Chanjiang River estuary and 40^.S, 226Ra specific activity was found to be relatively uniform with a mean value of 1.07 Bq/m3 （n= 19, SD=0.14）, similar to that of the open ocean. From 40^.S to 65^.S, 226Ra specific activity increased intensively, then decreased moderately further southwards. Near the Antarctic shore, it increased again, to 2.31 Bq/m3. This distribution was controlled by a combination of deep water upwelling, Southern Ocean fronts, water mixing and the continental 226Ra import. In Prydz Bay and the adjacent sea area, the mean 226Ra activity value was 2.26 Bq/m3 （n=31, SD=0.28）, with a relatively higher value outside of the bay and low 226Ra activity value in the center of the bay. This was consistent with the topography and hydrological setting of the bay. In addition, we extended the study area northward to the Arctic, by combining the published Z26Ra dataset for surface water from the Bering Sea to the Japan Sea. We also discuss the 226Ra distribution of high latitude oceanic surface water and its mechanisms.
