During the 13th (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&...During the 13th (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′S, 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 226Ra 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
Along the downwelling coast off Western Australia, late-austral-autumn/early-austral-winter chlorophyll a blooms are observed on the continental shelf south of the Shark Bay (26° S). The late-austral-autumn/early...Along the downwelling coast off Western Australia, late-austral-autumn/early-austral-winter chlorophyll a blooms are observed on the continental shelf south of the Shark Bay (26° S). The late-austral-autumn/early-austral-winter blooms are in phase with seasonal strengthening of the Leeuwin Current and its eddy field. From satellite altimeter and ocean color data , anticyclonic eddies are found to entrain the high phytoplankton biomass waters from the shelf and transport them offshore into the oligotrophic, subtropical marine environment. The late-austral-autumn/early-austral-winter blooms are highly linked with enhanced horizontal mixing by mesoscale eddies in the region, as derived from the finite-size Lyapunov exponent (FSLE) of the surface geostrophic flow field obtained from satellite altimeter data. The pathways of cross-shelf exchanges, which are mostly driven by the mesoscale eddies, are revealed with coalescing of the FSLE of the surface geostrophic flow field and the satellite chlorophyll a images.展开更多
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 13th (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′S, 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 226Ra 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.
基金supported by Strategic Research Fund for Marine Environment
文摘Along the downwelling coast off Western Australia, late-austral-autumn/early-austral-winter chlorophyll a blooms are observed on the continental shelf south of the Shark Bay (26° S). The late-austral-autumn/early-austral-winter blooms are in phase with seasonal strengthening of the Leeuwin Current and its eddy field. From satellite altimeter and ocean color data , anticyclonic eddies are found to entrain the high phytoplankton biomass waters from the shelf and transport them offshore into the oligotrophic, subtropical marine environment. The late-austral-autumn/early-austral-winter blooms are highly linked with enhanced horizontal mixing by mesoscale eddies in the region, as derived from the finite-size Lyapunov exponent (FSLE) of the surface geostrophic flow field obtained from satellite altimeter data. The pathways of cross-shelf exchanges, which are mostly driven by the mesoscale eddies, are revealed with coalescing of the FSLE of the surface geostrophic flow field and the satellite chlorophyll a images.
