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Abstract: The Norwegian Ecological Model (NORWECOM) biophysical model system implemented with the ROMS ocean circulation model has been run to simulate conditions over the last 25 years for the North Atlantic. Modeled time series of water volume fluxes, primary production, and drift of cod larvae through their modeled ambient temperature fields have been analyzed in conjunction with VPA estimated time series of 3-year-old cod recruits in the Barents Sea. Individual time series account for less than 50% of the recruitment variability; however, a combination of simulated flow of Atlantic water into the Barents Sea and local primary production accounts for 70% of the variability with a 3-year lead. The associated regression predicts increased recruitment between 2007 and 2008 from about 450–700 million individuals with a standard error of nearly 150 million. [Copyright &y& Elsevier]

Based on a ship survey during January 1998, the characteristics of the flow, the thermohaline properties and the volume transport of the Arabian Sea are discussed. A strong westward flow exists between 10.5°N and 11°N, part of which turns to the south as the Somali current near the coast at about 10°N and the rest turns north. At the passage between the African continent and the Socotra Island, the northern branch separates into two flows: the left one enters the passage and the right one flows eastward along the southern slope of the island. Off the island the flow separates once more, most of it meandering northeast and a small fraction flowing southeast. Volume transport calculation suggests that the tidal transport is one or two orders of magnitude smaller than the total transport in this region and it becomes more important near the coast. The average velocity of the flow in the upper layer (0–150 m) is about 20 cm s−1, with a maximum of 53 cm s−1 appearing east of the Socotra Island, and the subsurface layer (200–800 m) has an average velocity of 8.6 cm s−1; the velocity becomes smaller at greater depths. The depth of the seasonal thermocline is about 100 m, above which there is a layer with well mixed temperature and dissolved oxygen. High-salinity and oxygen-rich water appears near the surface of the northern Arabian Sea; a salinity maximum and oxygen minimum at 100 m depth along 8°N testifies the subduction of surface water from the northern Arabian Sea. Waters from the Red Sea and the Persian Gulf also influence the salinity of the area. [ABSTRACT FROM AUTHOR]

Abstract: A purely continuum theory for the thermophoretic velocity of aerosol and hydrosol particles in the zero Knudsen number, near continuum limit, , valid for both gases and liquids, is proposed. This theoretical result is based upon a fundamentally modified version of the traditional equations governing continuum fluid motion, one which accounts for an intrinsic difference in a fluid''s barycentric (mass-based) velocity and its kinematic velocity of volume, this difference arising during molecular transport processes in fluids within which a mass density gradient exists. Our continuum-scale approach contains no free parameters, nor does it rely upon any sub-continuum, molecular concepts, such as Maxwell''s thermally-induced velocity-slip condition. The resulting expression for the thermophoretic velocity of a non-Brownian, spherical particle agrees both constitutively and phenomenologically with available correlations of such velocity data in gases, as well as with the more limited data for liquids. Furthermore, the effect of shape and orientation is discussed for the case of non-spherical particles, with specific results furnished for effectively non-conducting particles. Agreement of the theory with the data furnishes explicit experimental support of the non-traditional fluid-mechanical equations utilized herein. [Copyright &y& Elsevier]

Abstract: Efficient monitoring of large-scale current systems for climate research requires the development of new techniques to estimate ocean transports. Here, a methodology for continuous estimation of dynamic height profiles and geostrophic currents from moored temperature sensors is presented. The technique is applied to moorings deployed in the Atlantic Deep Western Boundary Current at 26.5°N, off Abaco, the Bahamas (WOCE ACM-1 array). Relative geostrophic currents are referenced using bottom pressure sensors and available shipboard direct velocity (lowered-ADCP) sections over the period of the deployment, to obtain a time series of absolute volume transport. Comparison with direct velocity measurements from a complete array of current meters shows good agreement for the mean transport and its variablity on time scales longer than 10 days, but larger variability in the current meter derived transport at time scales shorter than 10 days. A rigorous error analysis assesses the contributions of various error sources in the geostrophic as well as direct transport estimates. Low-frequency drift of the bottom pressure sensors is found to be the largest error source in the geostrophic transport estimates and recommendations for improvement of the technique and related measurement technologies are made. [Copyright &y& Elsevier]

Abstract: Two moorings were deployed at 168°30′E (Sta. WPW) and 169°30′E (WPE) on 18°20′N in Wake Island Passage (WIP) to measure the velocity of the eastern branch of the deep western boundary current (DWBC) in the North Pacific. We obtained hourly velocity data from eight current meters located at depths of 3020, 4020, 5020, and 5120m (near-bottom) at WPW and 2000, 4000, 5000, and 5300m (near-bottom) at WPE, and analyzed daily mean velocity data for 374 days from 10 February 1999 to 18 February 2000. The velocity of the DWBC and its variations are large near the ocean floor, at depths of 5000m and more. The DWBC at WPE increases exponentially with depth, with the near-bottom mean velocity being 3.5cms−1, whereas the DWBC at WPW is almost uniform at the bottom layer with the mean velocity being 1.9cms−1. The direction of the DWBC in WIP is dominant between 15 and 55°T with a mean of approximately 35°T. This orientation is due to the direction of the bottom topography around 5000-m depth. The velocity and its variations decay markedly at 4000m, indicating the characteristics of the eastern branch current of the DWBC, which is formed primarily by the portion of the DWBC below 4500m. A peculiar property is that the velocity and its variations of the DWBC are much less in the western part (WPW) than in the eastern part (WPE) of WIP. The presence of several seamounts may decrease the velocity and modify the structure of the DWBC in the western half of WIP. On the other hand, the eastern half of WIP is deep and has no significant seamounts, which may enable the DWBC to flow smoothly there. The volume transport of the DWBC in WIP is estimated to be 3.6±1.3Sv (106 m3 s−1) northward on average, with a range of −5.3–14.8Sv, although the uncertainty of the mean value must be larger than 1.3Sv because of the estimation from just two moorings. The mean volume transport of the eastern branch current of the DWBC is found to be a little more than 3.6Sv by adding the transport in the passages west of WIP. The velocity and volume transport of the DWBC vary markedly with a period of approximately four months. A pause of the DWBC occurs in relation to the four-month variation. At WPW, the velocity and its variations at 4020m are similar to those at 3020m. The variations are sinusoidal with a four-month period, being almost out of phase with those at WPE. These are interpreted to be an eddy that may be propagated by Rossby waves and trapped in WIP. The four-month variations of the DWBC may be due to interaction with the eddy. [Copyright &y& Elsevier]

Abstract: Four bottom-mounted current profilers were deployed across the Taiwan Strait from September 28 to December 14 of 1999 to monitor the current velocity when the northeast monsoon was strong. Results indicate both diurnal and semidiurnal tidal currents were primarily barotropic. The barotropic diurnal tide might be explained by a single Kelvin wave propagating along the Mainland China coast from north to south. However, the barotropic semidiurnal tide manifested as a more complicated form in the Taiwan Strait. The subtidal current generally fluctuated with the northeast winds. When the northeast wind was weak, the along- and cross-strait subtidal current flowed primarily against the wind and toward Taiwan, respectively. As the northeast wind intensified, the along-strait current flowed downwind, brought the cold China coastal water southward, and formed a baroclinic velocity front in the western portion of the Taiwan Strait. The Ekman effect forced the cross-strait current toward Mainland China in the upper water column and toward Taiwan in the lower water column, respectively. The along-strait volume transport, estimated from interpolated current velocity, varied from −5 to 2Sv with a mean value of 0.12±0.33Sv. Similar transport was also estimated from the sea level difference across the Taiwan Strait. Although the local wind played a dominant role for the fluctuations of current velocity and transport in the Taiwan Strait, it could be not the only important factor. The current or transport directed frequently against the wind could be related to the northward current, which was consistently observed in the Penghu Channel. [Copyright &y& Elsevier]

The seasonal cycle in the Atlantic inflow to the Barents Sea is investigated by using 4-year long records from moored current meters, additional moorings of shorter duration, and hydrographic measurements. A higher transport during winter than summer is most common, but in years where the Barents Sea climate changes from a climatically cold to a climatically warm period (and probably vice versa), it may differ substantially from this. The higher transport during winter is related to barotropic currents that are forced by sea-level changes within the section induced by a shear in the cross-section wind stress, although possibly enhanced by variations in the remotely forced Norwegian Atlantic Current. The seasonal variation within the section is not uniform, and the strongest seasonal signal is found in the middle and northern parts. In the area near 71°30′N the wind (both speed and direction) changes substantially from winter to summer, without changes of the net Ekman transport. The water-level gradient, and the associated barotropic current, therefore has no seasonal variation in this area. However, there is a seasonal signal in the front between the Atlantic and Coastal Waters near the Norwegian Coast. This is due to coastal downwelling during winter that is forced by strong southwesterly winds. The mean transport of Atlantic Water is estimated to 1.7 Sv (1 Sv=106 m3 s-1) during winter and 1.3 Sv during summer, but there is a pronounced minimum in Atlantic inflow (or even outflow) in spring due to an annual event of northerly winds. [Copyright &y& Elsevier]

The Mahanadi River is one of the largest river systems in the east coast of Indiaand the estuary drains and communicates with the Bay of Bengal. The seasonallyvarying fresh water river discharge and the intrusion of salt water from the baydepend on the flow associated with the semi-diurnal component of the astronomicaltide (dominated by M2 component). A numerical model has been developed tosimulate and study the salinity structure, velocity profile, flow and circulation patternand have been compared with the observed data. A reasonably good agreement isnoticed between the model simulations and the observations. The model result hasbeen utilised to compute sediment load transport to the estuary channel over a tidalcycle as well as on a monthly time scale. The sediment load transport owing to monthlyclimatological rainfall is discussed and it is inferred that a dynamic equilibrium existson a long-term over good/bad monsoons. [ABSTRACT FROM AUTHOR]

The Gulf of Finland is a 400-km long and 48–135-km wide tributary estuary of the Baltic Sea featuring the longitudinal two-layer estuarine flow modified by transverse circulation. Longitudinal volume transport in the deep layer is investigated by decomposing it into an averaged, slowly changing estuarine component (due to large-scale density gradients, river discharge and mean wind stress) and wind-driven fluctuating component. The derived expression relates the total deep-layer transport to the projection of wind stress fluctuation to a site-specific direction. The relationship is tested and calibrated by the results from numerical experiments carried out with the three-dimensional baroclinic circulation model. For the entrance to the Gulf of Finland, winds from northeast support standard estuarine circulation and winds from southwest work against the density-driven and riverine flow. The deep estuarine transport may be reversed if the southwesterly wind component exceeds the mean value by 4–5.5 m s−1. According to the data from hydrographic observations in the western Gulf of Finland, an event of advective halocline disappearance was documented in August 1998. Comparison of the deep-water transport estimates calculated from the wind data in 1998 with the observed salinity variations showed that the events of rapid decay of estuarine stratification were coherent with the estimated reversals of deep-layer volume transport, i.e. events of salt wedge export from the gulf. [Copyright &y& Elsevier]

The monthly and annual mean freshwater, heat and salt transport through the open boundaries of the South and East China Seas derived from a variable-grid global ocean circulation model is reported. The model has 1/6° resolution for the seas adjacent to China and 3° resolution for the global ocean. The model results are in fairly good agreement with the existing estimates based on measurements. The computation shows that the flows passing through the South China Sea contribute volume, heat and salt transport of 5.3 Sv, 0.57 PW and 184 Ggs−1, respectively (about 1/4) to the Indonesian Throughflow, indicating that the South China Sea is an important pathway of the Pacific to Indian Ocean throughflow. The volume, heat and salt transport of the Kuroshio in the East China Sea is 25.6 Sv, 2.32 PW and 894 Ggs−1, respectively. Less than 1/4 of this transport passes through the passage between Iriomote and Okinawa. The calculation of heat balance indicates that the South China Sea absorbs net heat flux from the sun and atmosphere with a rate of 0.08 PW, while the atmosphere gains net heat flux from the Baohai, Yellow and East China Seas with a rate of 0.05 PW. [ABSTRACT FROM AUTHOR]

The characteristics of the Kuroshio axis south of Kyushu, which meanders almost sinusoidally, are clarified in relation to the large meander of the Kuroshio by analyzing water temperature data during 1961–95 and sea level during 1984–95. The shape of the Kuroshio axis south of Kyushu is classified into three categories of small, medium, and large amplitude of meander. The small amplitude category occupies more than a half of the large-meander (LM) period, while the medium amplitude category takes up more than a half of the non-large-meander (NLM) period. Therefore, the amplitude and, in turn, the curvature of the Kuroshio axis is smaller on average during the LM period than the NLM period. The mean Kuroshio axis during the LM period is located farther north at every longitude south of Kyushu than during the NLM period, with a slight difference west of the Tokara Islands and a large difference to the east. A northward shift of the Kuroshio axis in particular east of the Tokara Islands induces small amplitude and curvature of the meandering shape during the LM period. During the NLM period, the meandering shape and position south of Kyushu change little with Kuroshio volume transport. In the LM formation stage, the variation of the Kuroshio axis is small west of the Tokara Islands but large to the east due to a small meander of the Kuroshio. In the LM decay stage, the Kuroshio meanders greatly south of Kyushu and is located stably near the coast southeast of Kyushu. [ABSTRACT FROM AUTHOR]

Interannual variations of sea level at the Nansei Islands and volume transport of the Kuroshio during 1967–95 are calculated by integrating variations carried by windforced Rossby waves. Effects of eddy dissipation and ocean ridges are considered. Ridge effect is inferred by comparing between the calculated and observed sea levels. The calculation is satisfactory to sea levels and Kuroshio transport for the whole period. They are mostly caused by Rossby waves forced by wind and modified by the ridges, and are due to barotropic wave primarily and the first baroclinic wave secondly. The calculated Kuroshio transport well represents variations of several-year scales with maximums in respective duration of the large meander (LM) of the Kuroshio, as well as bi-decadal variation that transport was small during the non-LM period of 1967–75 and large during the LM-dominant period of 1975–91. Mean volume transport of the subtropical gyre is estimated at 57 Sv (1 Sv = 106 m3s−1) and divided by the Nansei Shoto Ridge into those of the Kuroshio in the East China Sea (25.5 Sv) and a subsurface current east of this ridge (31.5 Sv). The Subtropical Countercurrent and a southward deep current east of the Izu-Ogasawara Ridge are estimated at 16 Sv and 7 Sv, respectively. The calculated transports of the Kuroshio and other subtropical currents reach maximums at every El Niño event due to strong excitement of upwelling barotropic Rossby wave. [ABSTRACT FROM AUTHOR]

The variability of the New Guinea Coastal Current (NGCC) and New Guinea Coastal Undercurrent (NGCUC) were examined from one year time series of current data from ADCP moorings at 2°S, 142°E and 2.5°S, 142°E. Change in the hydrographic structure induced by monsoonal wind forcing was also examined from hydrographic data along the 142°E covering consecutively two winter seasons and two summer seasons. The westward NGCUC was observed to persist year around. The annual mean depth of the current core was 220 m, the mean speed of the zonal component was 54 cm/s with a standard deviation of 15 cm/s at the 2.5°S site. Velocity fluctuations at 20–30 day period were observed year around. Seasonal reversal of the surface intensified NGCC was clearly observed. In the boreal summer characterized by the southeasterly monsoon, westward currents of over 60 cm/s were dominant in the surface layer. The warm, low-salinity layer thickened at this time and sloped down toward the New Guinea coast from the equator. This surface water accumulation may be caused by onshore Ekman drift at the New Guinea coast, combined with weak Ekman upwelling at the equator. In the boreal winter, an eastward surface current developed to 100 cm/s extending down to 100 m depth in response to the northwesterly monsoonal winds. Coastal upwelling was indicated in this season and the surface water accumulated at the equator due to Ekman convergence. Shipboard ADCP data indicated that the NGCUC intensified in boreal summer as the width and depth of the NGCUC increased. [ABSTRACT FROM AUTHOR]

The Kuroshio Current has a considerable impact on the environmental characteristics and dynamic of the East China Sea (ECS). On the ECS continental shelf within the study area of (124°E-126°E, 25°N-27°N), the Kuroshio Branch Current (KBC) exists in a stable state and flows towards the main Kuroshio axis. The significant difference in potential vorticity is on both sides of the Kuroshio main axis, which makes it difficult for the seawater on the right side of the Kuroshio main axis to intrude the ECS continental shelf. Based on Argo data, satellite data and reanalysis data, an abnormal reverse intrusion of the KBC was observed during the passage of super typhoon Soudelor in 2015. The mean reverse volume transport during the period of Soudelor reached about 0.56 Sv, and the daily mean volume transport on August 9 reached up to 1.29 Sv. Soudelor inputted additional positive potential vorticity fluxes on the right side of the Kuroshio main axis and counteracted the significant potential vorticity difference on both sides of the Kuroshio main axis, which provided a channel for the apparently reverse enhanced ocean current. The significant Ekman downwelling and changes of the upper ocean stratification also promoted the reverse intrusion of KBC. This study offers new insights into the influence of typhoons on the intrusion of the Kuroshio onto the ECS continental shelf. ● A reverse intrusion of the Kuroshio Branch Current to the continental shelf under the influence of super typhoon has been discovered for the first time. ● The maximum reverse transport volume was up to 1.29Sv. ● The dynamic mechanism of reverse seawater intrusion is analysed. [ABSTRACT FROM AUTHOR]

The Alaskan Stream is the westward boundary current of the North Pacific subarctic gyre. In the central region of the North Pacific, the Alaskan Stream serves as a connection between the Alaskan gyre, Western subarctic gyre and Bering Sea gyre. Its volume transport is very important in estimating the magnitude of the subarctic circulation in the North Pacific. In order to clarify its seasonal and interannual variation, we conducted observations along a north-south section at 180° during June from 1990 to 1997. Moorings were deployed from 1995 to 1997. Hydrographic casts were made at intervals of ∼37 km to a depth of 3000 m. Moorings were set between CTD stations, with Moor1 (Moor2) at the center (southern edge) of the Alaskan Stream. Geostrophic volume transport (referred to 3000 m) revealed large interannual variability in the Alaskan Stream. Average volume transport over the 8 years was 27.5 × 106 m3s-1 with a standard deviation of 6.5 × 106 m3s-1. Maximum transport was 41.0 × 106 m3s-1 (1997) and minimum was 21.7 × 106 m3s-1 (1995). Stable westward flows were observed at Moor1 1500 m (259°, 11.7 cm s-1) and 3000 m (240°, 3.7 cm s-1, 1996–1997 year average). The ratio of eddy to mean kinetic energy ( KE′/ $$\overline {KE} $$ ) was very small (<0.6) throughout the year. A relatively weak and unstable westward flow was observed at Moor2 at 3000 m depth. Conversely, the average flow direction at Moor2 5000 m was eastward. [ABSTRACT FROM AUTHOR]

We examine results from a cruise in May 1997. CTD casts to near the bottom were made south of the Aleutian Islands, across Amchitka Pass, and north of the islands. We computed a westward geostrophic speed of 123 cm s−1 at 173.5°W in the Alaskan Stream. The computed volume transport there, referred to the bottom, was 25×106m3s−1. On other similar sections, transports were 8–15 × 106 m3s−1. Various complex variations in geopotential height along the Stream apparently altered the cross-stream gradients, and hence the transports. Rotational tendencies were also present. Northward inflow through Amchitka Pass was quite strong (6 × 106 m3s−1). Data north of the islands supported the existence of a zero-velocity reference level of variable depth. [ABSTRACT FROM AUTHOR]

A spatially varying non-stationary gravest empirical mode (GEM) field is constructed by incorporating the calendar month as an extra parameter to infer the subsurface thermohaline structure from the Pressure-sensor equipped Inverted Echo Sounder (PIES) observations in the western equatorial Pacific Ocean. This monthly GEM (MGEM) overcomes the application limitation of traditional GEM in the equatorial ocean due to the poor vertical coherence thermohaline structure there. The MGEM can capture 77% of the thermohaline variance for the upper 500 dbar, which is only 62% by the traditional GEM method. The most significant improvement of MGEM is for the deep ocean between 500 and 1900 dbar, where only 12% of the thermohaline variance can be captured by the GEM, but improved to 44% by the MGEM method. Based on the MGEM, a 24-month volume transport time series is estimated from observations by three PIESs deployed across the nascent North Equatorial Countercurrent (NECC) at 4°N, 6°N, and 8°N along the 130°E transect during 2014–2016. By establishing an empirical relationship between the 24 month-long volume transport and the synchronous altimeter data, a 24 year-long time series of NECC volume transport during 1993–2016 are constructed, and the seasonal and interannual variations of the NECC are investigated. The nascent NECC between 4°N-6°N was found to have quite strong seasonal variations with the strongest transport of 23 Sv occurring in February and the weakest transport of 11 Sv occurring in September. It is strengthened during the developing phase of El Niños, and is weakened during La Niñas. The 2015/16 El Niño exerts a significant impact on the nascent NECC with the amplitude comparable to that of the 1997/98 event, which even obscures the NECC's seasonality. • Pressure-sensor equipped Inverted Echo Sounder (PIES) observations in the western equatorial Pacific Ocean for the first time. • Development of a 3-dimensional GEM field with the third axis being time-of-year (MGEM field). • Significant improvement of MGEM in capturing thermohaline variance of deep ocean between 500 and 1900 dbar. • The nascent NECC has strong seasonal variations with its transport being doubled in winter compared with that in fall. [ABSTRACT FROM AUTHOR]

Subsurface-intensified anticyclones are ubiquitous in the ocean, yet their impact on the large-scale transport of heat, salt and chemical tracers is poorly understood. These submesoscale coherent vortices (SCVs) can trap and advect waters thousands of kilometers away from the formation region, providing a transport pathway that is unresolved by low-resolution Earth System Models. However, knowledge of the importance of these eddies for the large scale circulation is hindered by the lack of systematic observations. Here, we take advantage of the global network of Argo floats to identify occurrences of these eddies, which appear as weakly stratified anomalous water masses with Gaussian-shaped vertical structures. We develop a general algorithm to detect subsurface eddies that have propagated away from their source region, and apply it to the database of Argo float profiles, resulting in roughly 4000 detections from more than 20 years of observations. We further group detections into regional populations to identify hot-spots of generation and mechanisms of formation. Analysis of regional SCV statistics reveals important sites of SCV generation in Eastern Boundary Upwelling Systems, marginal sea overflows, and mode water formation regions along major open-ocean fronts. Because of the heat and salt anomaly contained within their cores, SCV could leave a significant imprint on the hydrographic properties of water masses in regions of high SCV density. • We develop and apply a new algorithm to detect submesoscale coherent vortices (SCVs) from Argo float profiles throughout the global ocean. • We identify and characterize regional SCV populations with consistent hydrographic properties. • We link notable SCV populations to their mechanisms of formation, and quantify their impact on regional hydrography. [ABSTRACT FROM AUTHOR]

Mapping small-scale high-precision velocity fields is of great significance to oceanic environment research. Coastal acoustic tomography (CAT) is a frontier technology used to observe large-scale velocity field in the horizontal slice. Nonetheless, it is difficult to observe the velocity field using the CAT in small-scale areas, specifically where the flow field is complex such as ocean ranch and artificial upwelling areas. This paper conducted a sound transmission experiment using four 50 kHz CAT systems in the Panzhinan waterway. Notably, sound transmission based on the round-robin method was recommended for small-scale CAT observation. The travel time between stations, obtained by correlation of raw data, was applied to reconstruct the horizontal velocity fields using Tapered Least Square inversion. The minimum net volume transport was 8.7 m3/s at 12:32, 1.63% of the total inflow volume transport indicating that the observational errors were acceptable. The relative errors of the range-average velocity calculated by differential travel time were 1.54% (path 2) and 0.92% (path 6), respectively. Moreover, the inversion velocity root-mean-square errors (RMSEs) were 0.5163, 0.1494, 0.2103, 0.2804 and 0.2817 m/s for paths 1, 2, 3, 4 and 6, respectively. The feasibility and acceptable accuracy of the CAT method in the small-scale velocity profiling measurement were validated. Furthermore, a three-dimensional (3-D) velocity field mapping should be performed with combined analysis in horizontal and vertical slices. [ABSTRACT FROM AUTHOR]

Instruments on two bottom-mount platforms deployed in the Bohai Strait during a cruise from January 6–13, 2018 recorded an intense northerly wind event. The responses of hydrodynamic and hydrographical characteristics in Bohai Sea and Yellow Sea to the wind event were analyzed aided by the wind, wave, sea surface suspended sediment concentration and sea surface height datasets from open sources. It is shown that the strong wind event had a significant impact on the redistribution of sea surface height, regional wave conditions, regional circulations and the accompanying sediment transport pattern. Specifically, the sediment transport through the Bohai Strait may be divided into two chronological phases related to the wind event: (1) the enhanced sediment transport phase during the buildup and peak of the wind event when both the Northern Shandong Coastal Current and regional suspended sediment concentration were sharply increased; and (2) the relaxation phase when the northerly wind subsided or even reversed, accompanied by the enhanced Yellow Sea Warm Current with lowered suspended sediment concentration. Such results at synoptic scale would improve our capability of quantifying sediment exchange between the Bohai and Yellow sea, through the Bohai Strait and provide valuable reference for the study of other similar environments worldwide. [ABSTRACT FROM AUTHOR]

To investigate the behavioral characteristics of the water temperature inversion layer (TIL), we used data (KODC) from areas in the Northern East China Sea from 1995 to 2016. Water temperature and salinity surveys were conducted 8820 casts over 22 years. Of these, 1589 water temperature inversion layers were found, and the probability of occurrence was 18.0%. In the Gageo island, probability of TIL occurrence in winter was 25 times higher than in summer. On the other hand, in the south of Jeju Island, summer values were 3.7 times higher than winter values. A T–S diagram analysis shows the components of the water temperature inversion layers. Yellow Sea Cold Water was mainly found in the winter, while Jeju Warm Currents and Tsushima Warm Currents were found in summer. The correlation between the probability of the occurrence of a monthly water temperature inversion layer and the amount of seawater volume transported into the study area was analyzed. The correlation coefficient was higher than r = 0.8 in parts of southern Jeju Island. On the other hand, the correlation coefficient was r = −0.6 in the Gageo Island. The spatial correlation index for the seawater volume transport and the water temperature inversion layer is presented. [ABSTRACT FROM AUTHOR]

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. • Time-series of in-situ measurements were collected simultaneously at two stations across the Bohai Strait. • Intermittent summer wind gusts altered the exchange flows through the Bohai strait, by temporarily raising the barotropic contribution to nearly 47% in an otherwise baroclinic-dominated summer pattern. • For the period of the measured summer wind gust, the net barotropic transports were one order of magnitude greater than the baroclinic counterparts. For the whole summer season, the barotropic transports also cannot be ignored. [ABSTRACT FROM AUTHOR]

Repeated glider surveys were conducted in the Japan Sea during April–June 2016. Observations revealed mesoscale hydrographic structures of the subpolar front, the Tsushima Warm Current, and eddies formed around flows in the central Japan Sea off Sado Island, in addition to fine-scale water properties associated with mesoscale variation. Data collected from satellite altimeters and thermometers, profiling floats, and ship conductivity–temperature–depth profiles were also analyzed to elucidate spatiotemporal characteristics in multiscale phenomena: mesoscale to fine scale. We present new quantitative estimates of the geostrophic volume transports of the Tsushima Warm Current and the subpolar front current in the central Japan Sea, based on hydrographic data from the glider's transects: they are, respectively, 2.5–2.7 Sv and 1.1–1.4 Sv. The mesoscale frontal/eddy structures varied greatly on a timescale of less than one month. We classified water masses, which revealed that the upper-layer, the low-salinity water within an anticyclonic eddy, was characterized in terms of salinity <34.0, potential density (σ θ) 25.5 kg m−3 < σ θ ≤ 26.1 kg m−3, and vertical thickness >100 m in this region, for which there are few hydrographic measurement data. • Repeated glider surveys were conducted in the Japan Sea during April–June 2016. • Results reveal large intra-monthly variability of mesoscale frontal structures. • The volume transport of the Tsushima Warm Current is estimated. • An upper-layer, low-salinity water was found within an anticyclonic eddy. [ABSTRACT FROM AUTHOR]

The oceanic response of the Taiwan Strait (TWS) to Typhoon Nesat (2017) was investigated using a fully coupled atmosphere-ocean-wave model (COAWST) verified by observations. Ocean currents in the TWS changed drastically in response to significant wind variation during the typhoon. The response of ocean currents was characterised by a flow pattern generally consistent with the Ekman boundary layer theory, with north-eastward volume transport being significantly modified by the storm. Model results also reveal that the western TWS experienced the maximum generated storm surge, whereas the east side experienced only moderate storm surge. Heat budget analysis indicated that surface heat flux, vertical diffusion, and total advection all contributed to changes in water temperature in the upper 30 m with advection primarily affecting lower depths during the storm. Momentum balance analysis shows that along-shore volume acceleration was largely determined by a combined effect of surface wind stress and bottom stress. Cross-shore directional terms of pressure gradient and Coriolis acceleration were dominant throughout the model run, indicating that the effect of the storm on geostrophic balance was small. This work provides a detailed analysis of TWS water response to typhoon passage across the strait, which will aid in regional disaster management. [ABSTRACT FROM AUTHOR]