Ice core obtained for crystallographic analysis, Athabasca River, Alberta (Canada), March 7, 2007
There are different types of river ice and one way of assessing ice type is by analysing an ice core sample. Sometimes the ice type can be identified directly from the ice core – for example the dirty layer in the photo above is frazil ice. Suspended frazil ice particles exhibit a highly adhesive behaviour in supercooled water and can pick up particles of sediment from the river bed before flocculating and floating up to the surface. But what’s above the dirty layer – is that snow ice or frazil ice? And is that clearer ice below columnar ice? The only way to really tell is to look at thin slices of the ice under polarized light. Then the individual crystals become visible.
(Photos by University of Alberta Rvier Ice Group.)