Occurring beneath a layer of snow.
The subnivean climate is the environment in and under the snowpack. Many animals spend an active winter here.
'Pukak' is an Inuit word for that environment.
Etymology: Latin 'sub', under + 'nives', snow.
Here is an article about the subnivean zone. The image below is from this site.
This word was posted by a friend on Facebook recently, and came to mind again as I shoveled snow today: it was a thin layer of snow, but some creatures had managed to use the cover, and left a network of small tunnels across my driveway.