TY - JOUR TI - The effect of wind and momentum advection in the James River estuary from field observations DO - https://doi.org/doi:10.7282/T32B8X28 PY - 2012 AB - From moorings deployed to the lower part of the James River (the southernmost tributary to the Chesapeake Bay), time series of velocity, salinity and pressure are collected for a length of 40 days. The time period covers one full spring and neap tide and both high wind and low wind scenarios. The velocity field, notably the lateral velocity and the calculated vertical velocity, as well as the salinity field are examined both spatially and temporally along a cross channel transect. Major findings include clear spring-neap variation in the lateral flow and little spring-neap variation in the longitudinal flow, persistent southward residual flow in the cross channel direction, tidal asymmetry in the vertical velocity, and tidal/subtidal variation in the salinity field. The wind effect is seen from augmented exchange flow and stratification after strong down estuary wind and weakened exchange flow and stratification after strong up estuary wind. It also impacts the lateral flow through Ekman dynamics as the down estuary wind introduces max southward flow and up estuary wind brings max northward flow in the cross channel direction. The role of advective acceleration in this estuary is examined through the momentum budget which includes three advective acceleration terms and two pressure gradient terms calculated from the data and the vertical stress divergence term inferred from the momentum balance. The outstanding advection comes from the second half of the ebb tide with different signs over different sides of the main channel. On both subtidal and tidal scales, it accelerates the along channel flow seaward over the southern shoal and landward over the northern channel and therefore superimposes additional residual flow structure to the along channel flow. The results, especially the advective acceleration being in the first order momentum balance in the upper layer, demonstrate that the along channel momentum balance is more complex than previously thought. KW - Oceanography KW - Winds--Measurement KW - Oceanography--Virginia--James River LA - eng ER -