Joekulhlaup initiation by ice-dam flotation: The significance of glacier debris content

Ice-dam flotation is a commonly described mechanism for the initiation of joekulhlaups (catastrophic floods) from ice-dammed lakes, but predictions of the critical lake depth required for flotation often differ from the actual lake depth at which flotation occurs. Glacier debris content is identified as an insufficiently recognized variable in ice-dam flotation. It is demonstrated that high debris contents could suppress flotation, and thereby affect the timing, mechanism and magnitude of catastrophic lake drainage events. The density of the part of the glacier forming the ice dam (rather than pure ice density) is the key to predicting ice-dam flotation.