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In field observations from a sinuous estuary, the drag coefficient (Formula presented.) based on the momentum balance was in the range of (Formula presented.), much greater than expected from bottom friction alone. (Formula presented.) also varied at tidal and seasonal timescales. (Formula presented.) was greater during flood tides than ebbs, most notably during spring tides. The ebb tide (Formula presented.) was negatively correlated with river discharge, while the flood tide (Formula presented.) showed no dependence on discharge. The large values of (Formula presented.) are explained by form drag from flow separation at sharp channel bends. Greater water depths during flood tides corresponded with increased values of (Formula presented.), consistent with the expected depth dependence for flow separation, as flow separation becomes stronger in deeper water. Additionally, the strength of the adverse pressure gradient downstream of the bend apex, which is indicative of flow separation, correlated with (Formula presented.) during flood tides. While (Formula presented.) generally increased with water depth, (Formula presented.) decreased for the highest water levels that corresponded with overbank flow. The decrease in (Formula presented.) may be due to the inhibition of flow separation with flow over the vegetated marsh. The dependence of (Formula presented.) during ebbs on discharge corresponds with the inhibition of flow separation by a favoring baroclinic pressure gradient that is locally generated at the bend apex due to curvature-induced secondary circulation. This effect increases with stratification, which increases with discharge. Additional factors may contribute to the high drag, including secondary circulation, multiple scales of bedforms, and shallow shoals, but the observations suggest that flow separation is the primary source., Environmental Fluid Mechanics

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Warner, J. C., Geyer, W. R., Ralston, D. K., & Kalra, T. Using tracer variance decay to quantify variability of salinity mixing in the Hudson River Estuary. Journal of Geophysical Research: Oceans, 125(12), (2020): e2020JC016096, https://doi.org/10.1029/2020JC016096., The salinity structure in an estuary is controlled by time‐dependent mixing processes. However, the locations and temporal variability of where significant mixing occurs is not well‐understood. Here we utilize a tracer variance approach to demonstrate the spatial and temporal structure of salinity mixing in the Hudson River Estuary. We run a 4‐month hydrodynamic simulation of the tides, currents, and salinity that captures the spring‐neap tidal variability as well as wind‐driven and freshwater flow events. On a spring‐neap time scale, salinity variance dissipation (mixing) occurs predominantly during the transition from neap to spring tides. On a tidal time scale, 60% of the salinity variance dissipation occurs during ebb tides and 40% during flood tides. Spatially, mixing during ebbs occurs primarily where lateral bottom salinity fronts intersect the bed at the transition from the main channel to adjacent shoals. During ebbs, these lateral fronts form seaward of constrictions located at multiple locations along the estuary. During floods, mixing is generated by a shear layer elevated in the water column at the top of the mixed bottom boundary layer, where variations in the along channel density gradients locally enhance the baroclinic pressure gradient leading to stronger vertical shear and more mixing. For both ebb and flood, the mixing occurs at the location of overlap of strong vertical stratification and eddy diffusivity, not at the maximum of either of those quantities. This understanding lends a new insight to the spatial and time dependence of the estuarine salinity structure., This study was funded through the Coastal Model Applications and Field Measurements Project and the Cross‐shore and Inlets Project, US Geological Survey Coastal Marine Hazards and Resources Program. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the US Government.

Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 126(1), (2021): e2020JC016771, https://doi.org/10.1029/2020JC016771., Estuaries worldwide have experienced modifications including channel deepening and intertidal reclamation over several centuries, resulting in altered fine sediment routing. Estuaries respond differently based on preexisting geometries, freshwater and sediment supplies, and extents and types of modification. The Coos Bay Estuary in Oregon is a relatively small estuary with complex geometry that has been extensively modified since 1865. A sediment transport model calibrated to modern conditions is used to assess the corresponding changes in sediment dynamics. Over ∼150 years, channel deepening (from ∼6.7 to 11 m), a 12% increase in area, and a 21% increase in volume have led to greater tidal amplitudes, salinity intrusion, and estuarine exchange flow. These changes have reduced current magnitudes, reduced bed stresses, and increased stratification, especially during rainy periods. Historically, fluvially derived sediment was dispersed across broad, deltaic‐style flats and through small tidal channels. Now, river water and sediments are diverted into a dredged navigation channel where an estuarine turbidity maximum (ETM) forms, with modeled concentrations >50 mg/L and measured concentrations >100 mg/L during discharge events. This “new” ETM supplies sediment to proximal embayments in the middle estuary and the shallow flats. Overall, sediment trapping during winter (and high river discharges) has increased more than two‐fold, owing to increased accommodation space, altered pathways of supply, and altered bed stresses and tidal asymmetries. In contrast to funnel‐shaped estuaries with simpler geometries and river‐channel transitions, these results highlight the importance of channel routing together with dredging in enhancing sediment retention and shifting pathways of sediment delivery., The Science Collaborative is funded by the National Oceanic and Atmospheric Administration and managed by the University of Michigan Water Center (NAI4NOS4190145)., 2021-06-14

These are the observational data collected in 2017 from the North River estuary. Data files include the long-term (LT) CTD and Aquadopp measurements from April to July, the short-term (STI from April to May and STII in late July) CTD measurements, eight shipboard CTD and ADCP surveys in April, May and July, the ADV measurements in late July, the North River mid-estuary region bathymetry, and the North River discharge (from USGS measurements)., National Science Foundation #1634480

Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 125(10), 2020): e2020JC016267, htps://doi.org/10.1029/2020JC016267., Flow separation has been observed and studied in sinuous laboratory channels and natural meanders, but the effects of flow separation on along‐channel drag are not well understood. Motivated by observations of large drag coefficients from a shallow, sinuous estuary, we built idealized numerical models representative of that system. We found that flow separation in tidal channels with curvature can create form drag that increases the total drag to more than twice that from bottom friction alone. In the momentum budget, the pressure gradient is balanced by the combined effects of bottom friction and form drag, which is calculated directly. The effective increase in total drag coefficient depends on two geometric parameters: dimensionless water depth and bend sharpness, quantified as the bend radius of curvature to channel width ratio. We introduce a theoretical boundary layer separation model to explain this parameter dependence and to predict flow separation and the increased drag. The drag coefficient can increase by a factor of 2–7 in “sharp” and “deep” sinuous channels where flow separation is most likely. Flow separation also enhances energy dissipation due to increased velocities in bends, resulting in greater loss of tidal energy and weakened stratification. Flow separation and the associated drag increase are expected to be more common in meanders of tidal channels than rivers where point bars that inhibit flow separation are more commonly found. The increased drag due to flow separation reduces tidal amplitude and affects velocity phasing along the estuary and could result in morphological feedbacks., Support for D. K. R. and the research leading to these results was funded by NSF award OCE‐1634480., 2021-04-14

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Geyer, W. R., Ralston, D. K., & Chen, J. Mechanisms of exchange flow in an estuary with a narrow, deep channel and wide, shallow shoals. Journal of Geophysical Research: Oceans, 125(12), (2020): e2020JC016092, https://doi.org/10.1029/2020JC016092., Delaware Bay is a large estuary with a deep, relatively narrow channel and wide, shallow banks, providing a clear example of a “channel‐shoal” estuary. This numerical modeling study addresses the exchange flow in this channel‐shoal estuary, specifically to examine how the lateral geometry affects the strength and mechanisms of exchange flow. We find that the exchange flow is exclusively confined to the channel region during spring tides, when stratification is weak, and it broadens laterally over the shoals during the more stratified neap tides but still occupies a small fraction of the total width of the estuary. Exchange flow is relatively weak during spring tides, resulting from oscillatory shear dispersion in the channel augmented by weak Eulerian exchange flow. During neap tides, stratification and shear increase markedly, resulting in a strong Eulerian residual shear flow driven mainly by the along‐estuary density gradient, with a net exchange flow roughly 5 times that of the spring tide. During both spring and neap tides, lateral salinity gradients generated by differential advection at the edge of the channel drive a tidally oscillating cross‐channel flow, which strongly influences the stratification, along‐estuary salt balance, and momentum balance. The lateral flow also causes the phase variation in salinity that results in oscillatory shear dispersion and is an advective momentum source contributing to the residual circulation. Whereas the shoals make a negligible direct contribution to the exchange flow, they have an indirect influence due to the salinity gradients between the channel and the shoal., The ideas in this paper were influenced by discussions with Robert Chant. Funding was provided by National Science Foundation grants OCE‐1325136, OCE‐1634490, and OCE‐1736539., 2021-04-29

We examine the direct relationships for both individual values and organizational-level culture on the quality of leader-member exchange (LMX) in a multilevel, multi-society study. In addition, we investigate the moderating roles of organizational- and societal- level cultures. Using 2343 respondents from 12 samples, we performed hierarchical linear modelling analysis and found that individual-level collectivism and organizational-level clan and hierarchy cultures were positively related to LMX, while individual-level individualism and organizational-level market and adhocracy cultures were negatively related to LMX. None of the organizational culture types or societal cultures had any moderating effects. One implication of the lack of moderating findings is that the main effect findings may be global, suggesting that they are not constrained by the organizational culture or societal culture in which they are embedded. We discuss additional implications for these findings.

Many single-country studies have examined compatibility between the individual values of the employee and organizational cultural values, typically referred to as person-organization (P-O) fit. However, little progress has been made in understanding whether P-O fit relationships generalize across countries and, if so, whether and how societal values impact this relationship. Because of this void, it is important to extend the P-O fit literature cross-culturally to explain not only how individual values relate to organizational values but also how societal values influence P-O fit relationships. Our study of 1,307 business professionals across six diverse countries focused on individualism/collectivism values at societal, organizational, and individual levels. We found that individual values are consistently congruent with organizational cultural values in individualistic societies, but found mixed results for P- O values fit in collectivistic societies. Our results provide more support for the contingency perspective (rather than the nested theory of culture) on how societal values influence P-O values fit relationships. Implications for the cross-cultural generalizability of extant P-O fit theory as well as for organizations are discussed.