My guess is this is hybrid is the same phase combo, just in winter pelt.
However, the red fox in this hybrid was likely a cross fox-because it looks like a very freaky cross fox!
It could even almost pass for a swift fox, which is a very close relative of the arctic fox– a much closer relative to it than the red fox is.
Perhaps they could produce fertile offspring, for it is well established that a fertile hybrid zone existswhere kit foxes and swift foxes share territory in New Mexico. At one time, they were regarded as belonging to the same species, but it has since been determined that swift foxes and kit foxes are as genetically divergent as swift foxes are from arctic foxes. That means that the swift fox could produce fertile offspring with an arctic fox– but I doubt that anyone would try to do this breeding experiment.
I should note that because of their relationship to red foxes and swift and kit foxes, the arctic fox is no longer in its own genus. It is now in the genus Vulpes, with the vast majority of the other true foxes.