"The world's ice sheets serve as cold-storage for creatures the Earth hasn't seen in eons. Scientists don't expect another Contagion or Andromeda Strain, but the release of unknown life forms does pose new concerns about effects of global warming."
"BOZEMAN, Mont. – Locked in frozen vaults on Antarctica and Greenland, a lost world of ancient creatures awaits another chance at life. Like a time-capsule from the distant past, the polar ice sheets offer a glimpse of tiny organisms that may have been trapped there longer than modern humans have walked the planet, biding their time until conditions change and set them free again.
With that ice melting at an alarming rate, those conditions could soon be at hand. Masses of bacteria and other microbes – some of which the world hasn't seen since the Middle Pleistocene, a previous period of major climate change about 750,000 years ago – will make their way back into the environment.
Once thought to be too harsh and inhospitable to support any living thing, the ice sheets are now known to be a gigantic reservoir of microbial life. Altogether, the biomass of microbial cells in and beneath the ice sheet may amount to more than 1,000 times that of all the humans on Earth."