Seasonal Variability Of Circulation Research Articles

Examining tidal impacts on seasonal circulation and hydrography variability over the eastern Canadian shelf using a coupled circulation-ice regional model

A coupled circulation and sea ice model is used to examine the tidal impacts on the seasonal variability of circulation, hydrography and sea ice over the eastern Canadian shelf (ECS). The model performance is assessed using in-situ and satellite remote sensing observations. The tidal impacts have significant spatial variability, which are relatively small over the Labrador and Newfoundland Shelves, moderate over the Scotian Shelf (ScS), and significant over the St. Lawrence River Estuary (SLRE), northwestern Gulf of St. Lawrence (GSL), southwestern ScS, Gulf of Maine (GoM), Bay of Fundy (BoF), and the northern flank of Georges Bank (GeB). The tidal impacts on the seasonal mean circulation are greater in winter than in summer in the SLRE, while greater in summer than in winter over several other areas in the GSL, the GoM-BoF and the southwest ScS. The tidal impacts on temperature and salinity are the most significant near fronts, where both tidal mixing and frontal circulation play important roles. The tidal residual circulation, especially that due to tidal rectification in the GSL and GoM-BoF, spreads the large tidal impacts generated near fronts into broader areas. The changes in circulation and stratification also account for the reduced sea ice concentrations in the GSL.

Seasonal variability of circulation and air-sea interaction in the Caspian Sea based on a high resolution circulation model

The Caspian Sea is the largest closed basin on Earth, with unique physical characteristics and complex bathymetry. Sparse measurements and coarse resolution models have not yet provided a full picture of its dynamics. In this study, a high resolution (∼3.3 km) Regional Ocean Modeling System (ROMS) was used to study its annual and seasonal circulation patterns, and distributions of salinity and temperature. Temperature and salinity nudging were implemented which forced the model to follow in situ observations. This approach effectively limited the model error in predicting the temperature and salinity. The model successfully reproduced sea surface temperature and salinity over the entire basin. The simulated sea surface salinity showed three salinity fronts over the Caspian Sea. The salinity profile was vertically uniform in deep waters of the Caspian Sea. In contrast, the vertical thermal structure formed the seasonal thermocline at a depth of 15–40 m which was intensified in summer. In general, the seasonal variability of water temperature or salinity was confined to the upper 100 m of the water column. Simulations revealed an impermanent weak northward current along the eastern coasts of the Middle Caspian Sea, a persistent strong southward current along its western coasts and a permanent deep anticyclonic gyre over the Southern Caspian Sea. Using a high resolution model, this study also reports several mesoscale and small scale structures in the Caspian Sea which have not been reported before.

Lagrangian Transport by Currents Variable in Time in the Model of Wind-Induced Circulation of the Black Sea

We construct a simple model of seasonal variability of circulation in the Black Sea, which satisfactorily explains the data of altimetric satellite observations. The model is used to describe the nonstationary wind-induced currents in a round basin and study the trajectories of water particles in the surface layer of the sea. It is shown that, for nonstationary currents, these trajectories can be quite complicated. It is also assumed that Lagrangian mixing can be caused by the complex trajectories of water particles.