Characteristics of the Changjiang plume and its extension along the Jiangsu Coast

Abstract

The major patterns of the Changjiang plume have been identified based on the Empirical Orthogonal Function and the freshwater flux analysis of the long-term model simulations driven by the climatological and realistic forcings. Dynamic natures of these patterns with respect to realistic forcings were analyzed. It was found that the Changjiang plume extends in three pathways: besides the two well-known major pathways that are spreading offshore to the northeast during the summer season and alongshore to the south in the winter season, a new pathway has been identified that occurs in both summer and autumn seasons as a small portion of the plume turns left and extends along the Jiangsu Coast, in a direction opposite to that of the coastally trapped wave (the upstream direction). Although its magnitude is smaller than the other two, it could be an important nutrients source for the frequently occurring algal blooming in that region. The major mechanism driving this plume branch is the tide-induced Stokes drift along the Jiangsu Coast, which results from the progressive tide from the East China Sea. This upstream-ward Stokes drift ends at ~33.5°N where it collides with the downstream-ward Stokes drift resulting from the rotating tide in the Yellow Sea. Consequently, the offshore Eulerian residual current is generated to move the diluted water offshore. Wind can also modulate this northward plume branch, however its effects are only significant during the neap tide.