Relative roles of Ekman transport and Ekman pumping in driving summer upwelling in the South China Sea(SCS) are examined using QuikSCAT scatterometer wind data.The major upwelling regions in the SCS are the coastal regions east and southeast of Vietnam(UESEV),east and southeast of Hainan Island(UESEH),and southeast of Guangdong province(USEG).It is shown that the Ekman transport due to alongshore winds and Ekman pumping due to offshore wind stress curl play different roles in the three upwelling systems.In UESEV,Ekman pumping and Ekman transport are equally important in generating upwelling.The Ekman transport increases linearly from 0.49 Sv in May to 1.23 Sv in August,while the Ekman pumping increases from 0.36 to 1.22 Sv during the same period.In UESEH,the mean estimates of Ekman transport and Ekman pumping are 0.14 and 0.07 Sv,respectively,indicating that 33% of the total wind-driven upwelling is due to Ekman pumping.In USEG,the mean Ekman transport is 0.041 Sv with the peak occurring in July,while Ekman pumping is much smaller(0.003 on average),indicating that the upwelling in this area is primarily driven by Ekman transport.In the summers of 2003 and 2007 following El Ni o-Southern Oscillation(ENSO) events,both Ekman transport and Ekman pumping decrease in UESEV due to the abnormally weak southwest monsoon.During the same events,however,Ekman transport is slightly enhanced and Ekman pumping is weakened in UESEH and USEG.
The variations of surface air temperature(SAT)over the Arctic are closely related to global climate change.Based on reanalysis datasets and a newly defined Aleutian Low intensity index,we found a good correlation between intensity of winter Aleutian Low and the SAT over the Arctic during the subsequent summer.Explanations were given using correlation analysis,composite analysis,and singular value decomposition methods.When intensity of winter Aleutian Low was weaker,sea surface temperature appeared higher in the North Pacific in the subsequent spring and summer,resulting in mean meridional circulation anomalies and 500 hPa geopotential height anomalies in spring and summer.Anomalous upward motion in mid-latitudes and downward motion in high latitudes(Ferrel cell weakening)transported the warmer air to the north from lower layer to the upper layer followed by increases in the SAT over the Arctic.Anomalous downward motion over about 75°N also caused consequent adiabatic warming and contributed to inhibit the heat transportation from surface to upper layer.Negative 500 hPa geopotential height anomalies existed in mid-latitudes and positive anomalies existed in high latitudes.The pattern(low-in-south and high-in-north)benefited from increasing the inflow volume flux of the Bering Strait,which also made the SAT over the Arctic increase.The results of this study reveal the process that the summer SAT over the Arctic was modulated by interannual variability of intensity of winter Aleutian Low.
On March 11,2011,a large earthquake and subsequent tsunami near the east coast of Japan destroyed the Fukushima Daiichi nuclear power plant(FD-NPP),causing a massive release of nuclear contaminants.In this paper,a Pacific basin-wide physical dispersion model is developed and used to investigate the transport of nuclear contaminants.The Pacific circulation model,based on the Regional Ocean Modeling System(ROMS),is forced with air-sea flux climatology derived from COADS(the Comprehensive Ocean-Atmosphere Data Set).It is shown that ocean current dominates nuclear contaminant transport.Following the Kuroshio Extension and North Pacific Current,nuclear contaminants at the surface will move eastward in the Pacific as far as 140°W,thereafter dividing into two branches.For the south branch,nuclear contaminants will be transported westward by the equatorial current,and can reach the Philippines after 10 years' time.In contrast,the north branch will arrive at the American west coast and then migrate to the Bering Sea.At 200 m water depth,part of the nuclear materials will move southwestward along with deep ocean circulation,which could potentially reach the east coast of Taiwan.The other part will move to the west coast of America and separate into two branches.One will move northward along the west coast of Alaska,while the other will travel southward to the Hawaiian Islands.The transport of radiation contaminants below 500 m is slow,and will primarily remain in the central Pacific.The physical dispersion model results show that high concentrations of the radioactive isotope cesium-137(137 Cs) will move eastward and reach the central Pacific and west coast of North America in two and eight years,respectively.The sea areas influenced by the nuclear contaminants continue to expand,while peak concentrations decrease in the North Pacific.
WANG HuiWANG ZhaoYiZHU XueMingWANG DaKuiLIU GuiMei
