The Investigation of Ice Melting Rates in Homogeneous Isotropic Turbulence

Abstract:

Melting of ice in the polar regions causes a significant portion of global sea level rise. Specifically, at ice-ocean interfaces such as tidewater glaciers or ice shelves, currents bring relatively warm salty water, thus producing temperature gradients and enhancing melting. Furthermore, turbulence generating processes such as buoyant meltwater plumes, tides, and density gradients increase the rate at which cold meltwater surrounding ice is replenished by warmer water, also driving melting in these locations. Currently absent from the literature is a thorough quantification of the effect turbulence, ambient water temperature, and salinity have on ice melting rates.

To understand the underlying physics of these parameters on melting rates, we designed an experimental facility that uses a random jet array to generate homogeneous isotropic turbulence absent mean flow in the center of a water tank. While in the ocean turbulence is typically found with waves and currents, baseline conditions can be established for ice sheet modeling applications with this fundamental experimental study. An ice sphere was placed stationary in the center of the tank. To determine the respective contributions to melting by temperature gradients compared to turbulence, melting rates were quantified under conditions varying ambient water temperature, salinity, and turbulence intensities. To calculate the velocity field surrounding the ice, particle image velocimetry (PIV) measurements were made. Turbulence statistics including turbulent kinetic energy, dissipation, spectra, and integral scales were computed from PIV data. Time-lapse photography was used to measure the melting rate while simultaneous laser-induced fluorescence (LIF) was used to quantify instantaneous melting dynamics to link to turbulent flow behavior.