Satellite remote sensing shows two hot spots of high suspended sediment concentration during the passage of Hurricane Irene (2011) over Chesapeake Bay: the shallow shoals in the mid Bay and the area around the mouth of the estuary. A coupled ocean wave sediment transport model is used to investigate mechanisms driving sediment resuspension and transport during the storm. The model reproduces the observed spatial variations of suspended sediment concentration and surface wave heights in the estuary and shows that both wave‐ and current‐induced shear stresses are important in stirring bottom sediment. In the mid‐Bay region, large wave‐induced shear stress causes sediment resuspension on the shallow shoals, while wind‐driven currents advect the suspended sediment downstream. Around the mouth of the estuary, the combined action of large waves and strong outflows produces high suspended sediment concentration, resulting in the export of ~0.8 Mt of estuarine sediments to the shelf. The storm‐induced sediment resuspension and export could be an important term in the sedimentary budget of an estuary.

A combined observational and numerical modeling study was conducted to clarify the effects of wind straining on estuarine stratification. Long‐term mooring observations in the middle of Chesapeake Bay showed an asymmetric stratification response to along‐channel winds. The stratification decreased under up‐estuary winds. Under down‐estuary winds, however, the stratification increased at moderate wind speeds but decreased at high wind speeds. In concert with numerical modeling, the mooring and ship‐based survey data were analyzed to test the wind‐straining mechanisms. In the middle and upper parts of the estuary, the straining of the density field by the vertical shear of the along‐channel current dominates the stratification response, enhancing stratification under the down‐estuary winds but reducing it under the up‐estuary winds. A regime diagram was constructed to place the wind‐induced stratification change in terms of the dimensionless Wedderburn number W: it is a linearly function of W for W > 0 (up‐estuary winds) but a parabolic function of W for W < 0 (down‐estuary winds). In the lower part of the estuary, however, the stratification response to the wind direction was opposite to that in the middle and upper Bay. The wind‐driven lateral circulation was much stronger there, and the cross‐channel straining of the density field by the vertical shear in the lateral currents drove the stratification response in the lower Bay. Therefore, both the along‐channel and cross‐channel straining regulate the estuarine stratification, and the net stratification change over a wind event is determined by the relative strength of along‐channel and cross‐channel straining.

Mooring data collected on the continental slope of the South China Sea (SCS) show that along‐slope deep sea bottom currents are generated when large spring internal tides (internal waves with tidal frequency) are observed, with the maximum velocity amplitude exceeding 0.15 ms^‐1. The observations are consistent with predictions that near‐bottom breaking of internal waves can result in generation of along‐slope flows when these waves obliquely approach the slope. A linear internal tide model in one horizontal dimension with realistic topography and stratification is used to show that the breaking of internal tides is likely due to near‐critical reflection on the slope. Combining the mooring observations and the model simulation, an along‐slope near‐bottom transport of ~0.5 Sv is estimated. Along‐slope bottom flows caused by breaking internal waves potentially provides a significant way to deform continental slopes and affect deep water exchange between the marginal sea and open ocean.

Tropical cyclones (TCs) are natural disasters for coastal regions. TCs with maximum wind speeds higher than 32.7 m/s in the north-western Pacific are referred to as typhoons. Typhoons Sarika and Haima successively passed our moored observation array in the northern South China Sea in 2016. Based on the satellite data, the winds (clouds and rainfall) biased to the right (left) sides of the typhoon tracks. Sarika and Haima cooled the sea surface ~4 and ~2 °C and increased the salinity ~1.2 and ~0.6 psu, respectively. The maximum sea surface cooling occurred nearly one day after the two typhoons. Station 2 (S2) was on left side of Sarika’s track and right side of Haima’s track, which is studied because its data was complete. Strong near-inertial currents from the ocean surface toward the bottom were generated at S2, with a maximum mixed-layer speed of ~80 cm/s. The current spectrum also shows weak signal at twice the inertial frequency (2f). Sarika deepened the mixed layer, cooled the sea surface, but warmed the subsurface by ~1 °C. Haima subsequently pushed the subsurface warming anomaly into deeper ocean, causing a temperature increase of ~1.8 °C therein. Sarika and Haima successively increased the heat content anomaly upper than 160 m at S2 to ~50 and ~100 m°C, respectively. Model simulation of the two typhoons shows that mixing and horizontal advection caused surface ocean cooling, mixing and downwelling caused subsurface warming, while downwelling warmed the deeper ocean. It indicates that Sarika and Haima sequentially modulated warm water into deeper ocean and influenced internal ocean heat budget. Upper ocean salinity response was similar to temperature, except that rainfall refreshed sea surface and caused a successive salinity decrease of ~0.03 and ~0.1 psu during the two typhoons, changing the positive subsurface salinity anomaly to negative

The 2-month-long mooring data were collected in a straight midsection of Chesapeake Bay to document the lateral circulation driven by along-channel winds. Under upestuary winds, the lateral circulation featured a clockwise (looking into estuary) circulation in the surface layer, with lateral Ekman forcing as the dominant generation mechanism. Under downestuary winds, however, the lateral circulation displayed a structure dependent on the Wedderburn number W: a counterclockwise circulation at small W and two counterrotating vortices at large W. The surface lateral velocity was phase locked to the along-channel wind speed. Analysis of the streamwise vorticity equation showed that the strength and structure of the lateral circulation in this stratified estuary were largely determined by the competition between the tilting of planetary vorticity by along-channel currents and lateral baroclinic forcing due to sloping isopycnals. Under strong, downestuary winds, the lateral baroclinic forcing offset or reversed the tilting of planetary vorticity on the western half of the estuarine channel, resulting in two counterrotating lateral circulation cells. A bottom lateral flow was observed in the deep channel and appeared to be generated by lateral Ekman forcing on the along-channel currents.