Ocean Circulation Dynamics in Semi-Enclosed Seas

Semi-enclosed seas, bounded by land and connected to the open ocean through narrow straits or sills, exhibit circulation patterns that are distinct from those of open basins. Their dynamics are governed by a combination of wind forcing, tidal energy, density gradients arising from temperature and salinity contrasts, and the exchange of water with the adjacent ocean. High evaporation rates in arid regions often drive an inverse estuarine circulation, in which fresher surface water enters from the open ocean while denser, salt-laden water returns at depth. Seasonal shifts in monsoonal winds and river discharge further modulate this exchange, producing strong temporal variability in current speeds, water properties and nutrient fluxes.

Numerical models and in situ observations have revealed the importance of narrow straits in controlling the volume and property fluxes between semi-enclosed basins and the open ocean. Tidal amplification, complex bathymetry and coastal geometry give rise to localized jets and recirculation gyres that influence sediment transport, larval dispersal and pollutant pathways. Thermohaline forcing, driven by surface heating and cooling, contributes to the formation of intermediate and bottom water masses that affect large-scale overturning and ventilation. Understanding these processes is essential for predicting the response of marginal seas to climate change, evaluating their role in regional heat and salt budgets, and supporting sustainable management of fisheries, desalination and coastal infrastructure.

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Ocean Circulation Dynamics in Semi-Enclosed Seas publication trend

The graph below shows the total number of articles in ocean circulation dynamics in semi-enclosed seas across all publications each year (not limited to Nature Index journals).

Technical terms

Semi-enclosed sea: A coastal basin largely surrounded by land and connected to the open ocean through narrow passages, with limited exchange.

Inverse estuarine circulation: A two-layer flow driven by net surface water loss, whereby fresh surface water enters the basin and denser saline water leaves at depth.

Total Exchange Flow (TEF): A bulk analytical framework that quantifies inflow and outflow across a section using property coordinates such as salinity or temperature.

Sverdrup (Sv): A unit of volumetric transport equal to one million cubic metres per second, commonly used in large-scale oceanography.

Hydrological budget: The balance of all water inputs and outputs in a basin, including evaporation, precipitation, river discharge and ocean exchange.

References

1. Hydrological Cycle in the Arabian Sea Region from GRACE/GRACE-FO Missions and ERA5 Data. Remote Sensing (2024).
2. Freshwater budget in the Persian (Arabian) Gulf and exchanges at the Strait of Hormuz. PLOS ONE (2020).
3. Numerical Study of the Exchange Flow of the Persian Gulf Using an Extended Total Exchange Flow Analysis Framework. Journal of Geophysical Research - Oceans (2020).