Scientific American: When permafrost thaws, microbes convert ancient organic matter in the frozen soil into climate-warming gases, like carbon dioxide and methane, potentially triggering a positive feedback loop that further melts the Arctic. But the once-barren soil also spouts new–and larger–shrubs that can act as a carbon sink, and scientists have wondered what the net effect of permafrost thawing would be on atmospheric carbon balance. A new study published this week in Nature suggests that changing …