National Geographic: Turns out there is such a thing as being too young and too thin. Arctic ice continued its decline this winter, with hardy, thicker old ice increasingly being replaced with quick-to-melt, thinner young ice, according to a new report by NASA and the National Snow and Ice Data Center. This winter’s maximum Arctic sea ice extent was 5.85 million square miles (15,150,000 square kilometers)–about 278,000 square miles (720,000 square kilometers) less than the Arctic average between …