U.S. scientists will head to the Arctic this week on a quest to map the ocean floor, and will collaborate with Canada on a surveying trip in September. The two nations — and their Arctic-bordering compatriots Russia, Denmark, and Norway — are scrambling to measure their respective continental shelves, with an eye to claiming as much as they can of the estimated 90 billion barrels of oil that could potentially become accessible if the Arctic gets melty enough. So how’s the northern region doing these days? “We thought Arctic ice cover might recover after last year’s unprecedented melting,” says Mark Serreze of the National Snow and Ice Data Center, but, “it now looks as if it will be a very close call indeed whether 2007 or 2008 is the worst year on record for ice cover over the Arctic.” Such conditions are, notes oceanographer Larry Mayer, “bad for the Arctic, but very, very good for mapping.”