Summer wind gusts modulate transport through a narrow strait, Bohai, China

Abstract

The hydrological and hydrodynamic response of Bohai Strait to an intense wind gust in the summer of 2016 was synthesized based on a 9-day in-situ observation at two mooring stations across the strait. At the north station, the sea level abnormally rose by 0.4 m during the wind gust. Strong subtidal inflow (into Bohai Sea) was observed during the gust, then changed to outflow after the gust subsided. At the southern station, the hydrographic property of water column changed rapidly with a strong outflow after the gust subsided. The Regional Ocean Modeling System model was employed to reconstruct the dynamic processes governing the event. It was found that wind-triggered sea level fluctuation caused the modulation of barotropic pressure gradient force, and thereby altered the exchange flow through the strait. Statistical analysis showed that a wind-triggered quasi-barotropic mode (controlled by sea level variation) contributed nearly 47% of the total variance. This suggests that during summer seasons that are normally dominated by baroclinic processes, the barotropic processes related to intermittent wind gusts also contribute considerably to the exchange flow and volume transport through the Bohai Strait.