Shell Oil announced Thursday that it's abandoning efforts to drill in icy waters off Alaska’s northern coast this year, a decision that prompted Alaska's senators to accuse the Obama administration of blocking access to large domestic supplies. The company’s plans to drill in Arctic waters have long been under attack from environmental groups. The Interior Department, after the BP oil spill, halted the oil giant’s plan to drill in 2010. Now the company – which is awaiting air quality permits and Interior’s permission – is throwing in the towel on 2011 too. The Houston Chronicle reports: