Had to bury a cat once in ground that was froze down to 10-12". I put a bag of charcoal down in the circle I needed, lit it on fire, covered it with a 55 gal drum on bricks so it was 5" off the ground, when charcoal was all burned it was thawed.

it wont take long even with the ground frozen depending on soil conditions a pick axe will make short work of the frozen dirt had to dig some hounds out of a coyote den one winter took about 2 hours of digging once got the frost it was easy going

A lot of how froze ground digs is determined by the type of soil and how wet it was when I froze. I have used a pick ax on froze ground here and can't say I thought it was a cure all. I would use the fire. A bored hole with a brace and bit and some diesel may help. If you could get some heat below ground level it would help thaw the sides. As it thaws enlarge your hole and do it again. Throw some coal down the hole with the diesel.

A lot of how froze ground digs is determined by the type of soil and how wet it was when I froze. I have used a pick ax on froze ground here and can't say I thought it was a cure all. I would use the fire. A bored hole with a brace and bit and some diesel may help. If you could get some heat below ground level it would help thaw the sides. As it thaws enlarge your hole and do it again. Throw some coal down the hole with the diesel.