The Columbia River (CR) estuary is characterized by high river discharge and strong tides that generate high velocity flows and sharp density gradients. Its dynamics strongly affects the coastal ocean circulation. Tidal straining in turn modulates the stratification in the estuary. Simulating the hydrodynamics of the CR estuary and plume therefore requires a multi-scale model as both shelf and estuarine circulations are coupled. Such a model has to keep numerical dissipation as low as possible in order to correctly represent the plume propagation and the salinity intrusion in the estuary. Here, we show that the 3D baroclinic discontinuous Galerkin finite element model SLIM 3D is able to reproduce the main features of the CR estuary-to-ocean continuum. We introduce new vertical discretization and mode splitting that allow us to model a region characterized by complex bathymetry and sharp density and velocity gradients. Our model takes into account the major forcings, i.e. tides, surface wind stress and river discharge, on a single multi-scale grid. The simulation period covers the end of spring-early summer of 2006, a period of high river flow and strong changes in the wind regime. SLIM 3D is validated with in-situ data on the shelf and at multiple locations in the estuary and compared with an operational implementation of SELFE. The model skill in the estuary and on the shelf indicate that SLIM 3D is able to reproduce the key processes driving the river plume dynamics, such as the occurrence of bidirectional plumes or reversals of the inner shelf coastal currents.

The paper deals with the classical ice engineering challenge of ice-induced vibrations (IIV) of offshore platforms. There is still a general industry concern with aspects of IIV and the load amplification that can arise in some situations resulting from ice interaction with a structure. It was thought important to re-visit current design methodology and practice, as well as the data that led to their formulation. A joint industry project (JIP) was organized, in which the main offshore oil companies joined together to sponsor development and validation of models for ice induced vibration. Broadly, the JIP: i) identified interesting aspects of the mechanisms behind IIV; ii) sponsored further development of three numerical modeling approaches chosen for the range of physics they captured; iii) and, provided calibrated models to an independent engineering company who used them to assess the model's accuracy in simulating five full-scale events whose data had been withheld from the model developers - ensuring an independent validation rather than a further fitting of models to data. This paper is a "briefing" and provides an overview of the background, progress, and some validation findings: a status report on the reliability of present procedures available to the offshore industry when designing platforms in moving ice where IIV can be expected. The "science" behind the models will be presented by the model developers themselves (e.g. Hendrikse & Metrikine, 2013) and in further publications once the JIP confidentiality conditions expire.