Spanning 10 billion scales from millimetre turbulence to global circulation

Speaker: 

Dr Bishakhdatta Gayen

Affiliation: 

Australian National University

Date: 

Mon, 27/08/2018 - 4:00pm

Venue: 

RC-3085, The Red Centre, UNSW

Abstract: 

The general ocean circulation, of crucial importance to the global climate, involves fluid motion on scales ranging from turbulence, internal waves, eddies and fronts, planetary Rossby waves and basin-scale gyre recirculation. Equilibrium is maintained between continuous large-scale forcing and energy dissipation. Understanding the physics of various dissipation mechanisms is important for improving the dynamical description of large-scale circulation. Large-scale ocean models do not accurately model turbulent convection, breaking waves, and turbulence, providing motivation to develop a better understanding of these mechanisms. In this presentation, the primary focus will be on understanding the role of turbulence and convection in ocean circulation.

In order to examine the effect of convection in ocean circulation, a model has been developed of circulation with flow driven by surface buoyancy in a closed basin using Direct Numerical Simulations. The circulation cell involves a horizontal boundary flow, turbulent plume motion and week interior return flow. Under planetary rotation, even in the absence of wind stress, the flow becomes three-dimensional with small-scale deep convection and broad basin-scale gyres. For the first time, DNS is used to model this circulation and quantify the heat transfer and flow energetics, demonstrating several dynamical regimes. The role of turbulent convection in melting of basal ice shelves and circulation around the Antarctic basin will also be discussed. 

 

Biography:

Dr Bishakhdatta Gayen is a Research Fellow at the Research School of Earth Sciences at Australian National University.  His current research interests are nonlinear internal waves in the ocean, turbulent convection, modeling of Antarctic ice melting and Southern ocean dynamics. Bishak was awarded an ARC DECRA fellowship in 2013, and received the RJL Hawke post-doctoral fellowship from the Australian Antarctic Science Program to study subsurface melting of ice shelves around Antarctic with implications for future global sea level rise.

School Seminar Series: