Publication Date:
2022-05-25
Description:
Author Posting. © American Meteorological Society, 2018. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 48 (2018): 607-623, doi:10.1175/JPO-D-17-0189.1.
Description:
The roles of straining and dissipation in controlling stratification are derived analytically using a vertical salinity variance method. Stratification is produced by converting horizontal variance to vertical variance via straining, that is, differential advection of horizontal salinity gradients, and stratification is destroyed by the dissipation of vertical variance through turbulent mixing. A numerical model is applied to the Changjiang estuary in order to demonstrate the salinity variance balance and how it reveals the factors controlling stratification. The variance analysis reveals that dissipation reaches its maximum during spring tide in the Changjiang estuary, leading to the lowest stratification. Stratification increases from spring tide to neap tide because of the increasing excess of straining over dissipation. Throughout the spring–neap tidal cycle, straining is almost always larger than dissipation, indicating a net excess of production of vertical variance relative to dissipation. This excess is balanced on average by advection, which exports vertical variance out of the estuarine region into the plume. During neap tide, tidal straining shows a general tendency of destratification during the flood tide and restratification during ebb, consistent with the one-dimensional theory of tidal straining. During spring tide, however, positive straining occurs during flood because of the strong baroclinicity induced by the intensified horizontal salinity gradient. These results indicate that the salinity variance method provides a valuable approach for examining the spatial and temporal variability of stratification in estuaries and coastal environments.
Description:
X. Li was supported by the China
Scholarship Council. W. R. Geyer was supported by
NSF Grants OCE 1736539 and OCE 1634480. J. Zhu
was supported by the National Natural Science Foundation
of China (41476077 and 41676083). H. Wu was
supported by the National Natural Science Foundation
of China (41576088 and 41776101).
Description:
2018-09-08
Keywords:
Ocean
;
Estuaries
;
Freshwater
;
Mixing
;
Numerical analysis/modeling
;
Regional models
Repository Name:
Woods Hole Open Access Server
Type:
Article
Permalink
