How deep can permafrost extend in northern Siberia?

In northern Siberia, permafrost is exceptionally deep, reaching thicknesses of 1,500 metres (5,000 feet). Some reports indicate that the deepest known permafrost in the region exceeds 2,000 feet.12

The depth of permafrost is influenced by several factors, including local climate, vegetation, topography, and the geological history of the area, such as whether it was previously covered by glaciers or sea ice. In unglaciated areas, very deep permafrost likely formed during the extreme cold of the ice ages.23