At the request of Dr. Johnson, this talk will not be recorded. Please email Dr. Blair Johnson for more information about her talk and her work.
Speaker: Blair Johnson, Maseeh Department of Civil, Architectural & Environmental Engineering, The University of Texas at Austin
Title: Enhancement of ice melting rates in isotropic turbulence
Host: Sara Santos
Abstract: Recently, numerical simulations have been found to underpredict ice loss of submarine glaciers. A major source of uncertainty is the effect of turbulence on melting, and how to properly account for energetic turbulent flows in modeling. Turbulence continually stirs cold meltwater immediately adjacent to submarine ice with relatively warmer or saline ambient fluid in the environment, promoting more efficient melting. However, the mechanism by which turbulence, when coupled with ambient salinity and temperature, increases melt rates is still unknown. To understand the fundamental physics by which ocean turbulence, temperature, and salinity affect melting rates, we designed a laboratory study that allows us to explore melting of a submerged ice sphere. We performed a baseline study with quiescent ambient water ranging in temperature from 2 to 10 degrees Celsius to explore the flow of convective currents and meltwater plumes with freshwater and saltwater. In subsequent tests, we performed experiments in homogeneous isotropic turbulence absent mean flow using a custom-designed apparatus at three different levels of turbulent kinetic energy. We use particle image velocimetry (PIV) to measure the velocity field and turbulence statistics of the ambient water and meltwater to study the unique boundary layer flows that develop. Using laser induced fluorescence (LIF), we are able to instantaneously couple flow dynamics with melting and quantify mixing of localized meltwater plumes. We present a full quantification of melting across a wide parameter space exploring contributions from ambient turbulence, temperature, and salinity. These experiments allow us to quantify key uncertain parameters that will improve models of glacier melting.