Grain growth of ice doped with soluble impurities

• Published in: The Cryosphere
• Main Authors: Q. Wang, S. Fan, C. Qi
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2024
• Subjects: Environmental sciences; GE1-350; Geology; QE1-996.5; The Cryosphere
• Online Access: https://doi.org/10.5194/tc-18-1053-2024; https://doaj.org/article/b127ac63fa07417986ec31723f42d308

The grain size of polycrystalline ice affects key parameters related to the dynamics of ice masses, such as the rheological and dielectric properties of terrestrial ice as well as the ice shells of icy satellites. To investigate the effect of soluble impurities on the grain-growth kinetics of polycrystalline ice, we conducted annealing experiments on polycrystalline ice samples doped with different concentrations of KCl (10 −2 , 10 −3 , 10 −4 and 10 −5 mol L −1 ) or MgSO 4 (10 −2 and 10 −5 mol L −1 ). Samples were annealed for a maximum of 100 h at a hydrostatic confining pressure of 20 MPa (corresponding to a depth of about 2 km) and different constant temperatures of 268, 263, 258 and 253 K (corresponding to − 5, − 10, − 15 and − 20 °C, respectively). After each experiment, images of a polished sample surface were obtained using an optical microscope equipped with a cold stage. With grain boundaries detected, grains were reconstructed from the images, and an average grain size was determined for each sample. Normal grain growth occurred in all samples. Grain-size data are interpreted using the following grain-growth model: d n - d 0 n = k t <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="63pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="460baa849c7d73d1781529949316097c"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="tc-18-1053-2024-ie00001.svg" width="63pt" height="15pt" src="tc-18-1053-2024-ie00001.png"/></svg:svg> ( d : grain size; d 0 : starting grain size; n : grain-growth exponent; k : growth constant; t : duration). Values of the best-fit grain-growth exponent, n , for all samples range from 2.6 to 6.2, with an average value of 4.7. Pure ice exhibits 3.1 ⩽ n ⩽ <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="29pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="85cb61edab7e06b832fc006f6ac93996"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="tc-18-1053-2024-ie00002.svg" width="29pt" height="10pt" ...