2. fissures and cracks are created in the brittle upper surface of glaciers as they pass over/around subsurface features, they do form a passage way for surface melt water to reach the base of glacers.
I forgot differential rates of movement account for them as well, however these are commonly associated with subsurface features as well but they are not a melt water feature as claimed by winnie.
Melt water sources - pressure and or geothermal - not friction. Water will reduce friction but is not caused by it that is the point of it all.
You may want to broaden your understanding of friction. It may be dynamic or static (and in the case of glaciers, both certainly exist). Both produce heat, as does torsion within the ice. Fissures can be a melt water feature - while the fissure may have started as a surface crack, running water and frost heave can certainly erode ice surfaces.