National Geographic: Arctic sea ice shrank drastically this summer, reaching a record low, largely because warm ocean currents ate away at the base of the ice sheet, new research says. Wind currents also played a key role, blowing sea ice south into the Atlantic Ocean, where the ice then melted, according to the research. With more global warming in store, researchers said, the prognosis is grim for the Arctic’s so-called perennial sea ice, which is the ice that survives through the …