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A high-resolution Arctic Ocean-Finite Volume Community Ocean Model (AO-FVCOM) and observational current data from 14 mooring stations in Bering Strait and surrounding regions between 1990 and 2015 were used to study the seasonal and in-terannual variability of Bering Strait throughflow (BST). AO-FVCOM represented the BST with a climatological northward flux of 1.06Sv, which was close to the observational mean of 0.94 + 0.26Sv. From the model results, the strongest volume flux was in summer, approximately 45% larger than that in winter. Interannual variability of BST was also indicated in the model results, and the maximum and minimum annual mean transports are in 2007 and 2012, respectively. AO-FVCOM showed larger differences from the observations in 2000, 2002, and 2015 than in other years, which may be related to the limitation of atmospheric forcing for the model. According to the driving mechanisms of BST, sea level difference (SLD) across the strait dominates the northward volume transport, and local wind is also important in forcing the seasonal variability of the BST and SLD patterns to change the BST indirectly.

Advances on the circulation in the Changjiang Estuary and adjacent East China Sea (ECS) and Yellow Sea (YS) coastal waters in the recent decades (2000–2020) are synthesized in this review. The circulation over the complicated bathymetry in the region is locally driven by winds, tides, as well as riverine discharge, and is remotely influenced by shelf currents between the 50 and 100-m isobaths through the cross-shelf exchanges. The interchange of the momentum and the freshwater pathway inside the Changjiang Estuary are jointly determined by tides and seasonally varying discharge and winds over the shelf. The buoyant waters are trapped inside the bulge that forms and expands over the shelf to the west of the 30-m isobath in the vicinity of Hangzhou Bay and the Changjiang Estuary. These buoyant waters are exported offshore by the shelf current, tidal mixing, and variations of wind patterns, forming the Changjiang River plume, which shows notable seasonality due to the reversal of both winds and shelf currents in the ECS and YS. Extensive spatial irregularities in the form of freshwater patches are present along its pathway to the Tsushima Strait in summer and to the Taiwan Strait in winter, respectively. Tides and the bathymetry irregularity have recently been found to play critical roles in determining the cross-shelf exchanges of water mass and momentum along the pathway of the ECS coastal current, and along this pathway, a year-round upslope intrusion of shelf waters appears in both summer and winter. Tides also play an important role in altering the expansion of the Changjiang River plume, cross-shelf extrusion of waters, and variation in the Yellow Sea Coastal Current over the shallow Subei Shoal.

This study reviews recent advances in the circulation dynamics of the Kuroshio and its interaction with shelf currents in the East China Sea (ECS). The annually averaged Kuroshio volume transport varies between 19 and 24 Sv, based on different observations, but there is not consensus on the season when its volume transport peaks. The Kuroshio is intensified over the central slope of the ECS from that to the northeast of Taiwan. The total Kuroshio intrusion into the ECS shelf is estimated to be approximately 1.4 Sv, deduced from the observed volume transport of exchange flow in the Taiwan and Tsushima Straits, based on the assumption of volume conversation over the shelf. However, the uncertainty regarding to this estimation remains due to the absence of sufficient observations and understanding of the Kuroshio dynamics and its interaction with the complex slope topography. The Kuroshio intrusions over the shelf to the northeast of Taiwan and southwest of Kyushu are stimulated by planetary or topographic β-effect associated with the alongshore variation in the ECS slope topography and altered by variations in the Kuroshio intensity, shear stress, and baroclinicity. Multilayered exchanges between the Kuroshio and shelf currents were found between 100 and 200 m isobaths along the central ECS slope. The spatial variation in these exchanges is governed by cross-isobath transport by geostrophy, whereas bottom Ekman transport plays a predominant role in altering the integrated exchange flow along the slope. Although the intrusion is greatly modulated along the path of the Kuroshio off the ECS by variable slope topography, there are few observations on spatial variation of these exchange flows. The characteristics and variations in circulation and hydrographic properties of waters between 100 and 200 m isobaths significantly determine the general ECS circulation, about which consensus has still not been attained.