Glaciohydraulic supercooling is potentially an important mechanism of basal ice formation with significant implications for Quaternary Science, but remains controversial. Some studies cite similarities between basal ice and the ice forming at vents of upwelling supercooled subglacial water as evidence that where supercooling occurs it dominates basal ice formation. Other studies find no evidence linking supercooling to basal ice even at glaciers where supercooling occurs, questioning the supposed genetic link between basal ice and vent ice. At Svínafellsjökull, southeast Iceland, we compare the physical characteristics and geographical distribution of stratified basal ice with the characteristics and distribution of phenomena such as upwellings and anchor ice terraces associated with supercooling. Two physically and geographically distinct basal ice populations emerge: one occurs only where there is evidence for glaciohydraulic supercooling and has physical characteristics consistent with an origin by supercooling; the other is ubiquitous, even at locations where there is no evidence for supercooling, and has characteristics consistent with non-supercooling modes of origin. We suggest that glaciohydraulic supercooling does not account for all of the basal ice at Svínafellsjökull, and that other mechanisms of basal ice formation are also significant.