Laser-light scattering from polar ice: Theory and experiment
Stolz, Michael Robert
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Laser-light scattering (LLS) is an accepted method for measuring the concentration of water insoluble aerosol deposits (dust) in polar ice. LLS on ice can also be used to measure water soluble aerosols, as well as imperfections (air bubbles and cavities) in polar ice. LLS was originally used on ice meltwater for measuring the dust concentration in polar ice, but was later also applied to ice directly, for measuring the dust concentration profile along deep, bubble-free sections of the Greenland Ice Sheet Project 2 (GISP2) ice core from central Greenland. In this dissertation, we present results that extend the usability of LLS on ice into the realm of the non-transparent, bubbly polar ice, and put previous empirical findings on a theoretical footing. For LLS on clear, bubble-free polar ice, we studied numerically the scattering of light by soluble and insoluble aerosol particles embedded in the ice to complement previous experimental studies. For air bubbles in polar ice, we calculated the effects of multiple light scattering using Mie theory and Monte Carlo simulations, and found a new method for determining the bubble size and number concentration using LLS on bubbly ice in conjunction with ice density measurements. We constructed a new, versatile and compact instrument, which allows the application of traditional, as well as new LLS methods, and we demonstrated that LLS can be used on bubbly ice to measure annual layers rapidly in an objective manner.