Date: 30 September 2020
Time: 14:00 (GMT+3)
Speaker: Assist. Prof. Dr. N. Berkay Basdurak
Title: Modeling the Dynamics of Small-Scale River and Creek Plumes in Tidal Waters
Our webinar series is continuing with Dr. N. Berkay Basdurak! He will present his research on Modeling the Dynamics of Small-Scale River and Creek Plumes in Tidal Waters. The talk will be given in English on the Zoom platform. Please note that there will be a limited number of spots available and the Institute members will be prioritized in case of overbooking. You can register via clicking the link below. After the registration, the meeting ID and password will be sent automatically via Zoom.
Abstract
The fate of discharges from small rivers and mountainous streams are little studied relative to the dynamics of large river plumes. Flows from small watersheds are episodic, forming transient low-salinity surface plumes that vary tidally due to interaction of outflow inertia with buoyancy and ambient tidal currents. An implementation of the Regional Ocean Modeling System (ROMS v3.0), a three-dimensional, free-surface, terrain-following numerical model is applied to small river outflows (≤10 m3s-1) entering a tidal ocean, where they form small plumes of scale ~103 m or smaller. Analysis of the momentum balance points to three distinct zones: (i) an inertia-driven near-field, where advection, pressure gradient, and vertical stress divergence control the plume dynamics, (ii) a buoyancy-driven mid-field, where pressure gradient, lateral stress divergence, and rotational accelerations are dominant, and (iii) an advective far-field, where local accelerations induced by ambient tidal currents determine the fate of the river/estuarine discharge. The response of these small tidal plumes to different buoyancy forcing and outflow rate is explored. With increasing buoyancy, plumes change from narrow/elongated, bottom-attached flows to radially-expanding, surface-layer flows. Weak outflow promotes stratification within the plume layer, and with stronger outflow the plume layer becomes thinner and well-mixed. When compared with prototypical large-river plumes in which Coriolis effects are important: (i) in these small plumes there is no bulge and no coastal buoyancy current i.e., shore contact is mostly absent; and (ii) the plume is strongly influenced by ambient tidal currents, forming a tidal plume that is deflected upcoast/downcoast from the river mouth.
Keywords: Small scale, river plume, creek plume, plume dynamics
Biography
Dr. N. Berkay Basdurak is a physical oceanographer. He obtained his M.Sc. from METU in 2004. He obtained his Ph.D. in coastal oceanographic engineering in 2010 from University of Florida. Following postdoctoral fellowships at the Bodega Marine Laboratory (University of California, Davis) and Leibniz Institute for Baltic Sea Research, he recently joined METU, Institute of Marine Science.
He studies the physical processes in estuaries and coastal seas.
His research interests span a wide range of topics including eddy viscosity parameterizations for tidally and wind driven estuarine exchange flow, small scale river plumes under varying atmospheric forcing, surface boundary turbulence at small scales (i.e., submesoscale processes and frontal dynamics). He is interested in processes at the interface between the traditional fields of oceanography and fluid dynamics. He seeks to understand how the diverse components, processes, and scales fit together.
