1. Exhumed fumes
The scariest entity to emerge from the melt so far is methane, a greenhouse gas 30 times more potent than CO2. Released when formerly frozen matter decomposes in thawed tundra, the gas boosts atmospheric temperatures, defrosting more acreage—a spine-chilling feedback loop.
Eideard 
Scientists Revive ‘Zombie’ Virus After 50,000 Years Trapped in Siberian Permafrost https://www.commondreams.org/news/2022/11/26/scientists-revive-zombie-virus-after-50000-years-trapped-siberian-permafrost
Researchers documented 13 never-before-seen viruses that have been lying dormant, frozen in thick ice, over tens of thousands of years.