In 2007, the Arctic lost a massive amount of thick, multiyear sea ice, contributing to that year's record-low extent of Arctic sea ice. A new NASA-led study has found that the record loss that year was due in part to the absence of "ice arches," naturally-forming, curved ice structures that span the openings between two land points. These arches block sea ice from being pushed by winds or currents through narrow passages and out of the Arctic basin....