"Thawing permafrost cracked the casing on a BP oil well earlier this year, starting a leak that continued for days."
"Alaska's main oil and gas regulatory body has ordered a review of all North Slope wells after a spill last spring was connected to thawing permafrost, subsidence and a cracked casing.
The emergency order, issued Monday by the Alaska Oil and Gas Conservation Commission (AOGCC), said the outer casing that cracked had been set in the permafrost.
In April, one of BP's older wells leaked oil and gas for days before it could be shut down. The company reported that roughly 45,000 kilograms of gas and 63 gallons of crude leaked. According to Alaska Public Media, BP blamed the failure then on a piece of a well casing that buckled under pressure from thawing permafrost."