Summertime Changjiang River plume variation during 1998-2010

Using an improved satellite-derived salinity algorithm in the East China Sea (ECS), we presented and examined a general view on summertime Changjiang River plume variation during 1998-2010. Three types of plume shapes were identified: (1) the commonly known northeastward transportation, (2) a case in which most of the plume water crossed the Cheju Strait into the Tsushima-Korea Straits with only a small fraction staying on the shelf of the ECS, and (3) a rare case in which the plume front moved southeastward. Satellite time-series data suggested that, during the peak river discharge time in July with favorable southwest monsoon, the plume area was highly correlated with the river discharge of the same month. Interestingly, the plume area in August was also dominated by the discharge in July. In August, as the direct effect of freshwater discharge weakening, the plume area also became positively correlated with wind speed in the 45 degrees and 60 degrees direction, suggesting that the plume extension was more influenced by the southwesterly wind during periods of smaller discharge. Furthermore, a few special cases with unique plume extensions were found under extreme weather conditions. Finally, we found no significant long-term trend of plume area change over 1998-2010 in summertime and concluded that the interannual variation was probably regulated by natural variation rather than anthropogenic effects, such as construction of the Three Gorges Dam. This study will have implications for biogeochemical and modeling studies in large river plume areas.