Reuters: The thickest, oldest and toughest sea ice around the North Pole is melting, a bad sign for the future of the Arctic ice cap, NASA satellite data showed on Tuesday. "Thickness is an indicator of long-term health of sea ice, and that’s not looking good at the moment," Walt Meier of the National Snow and Ice Data Center told reporters in a telephone briefing. This adds to the litany of disturbing news about Arctic sea ice, which has been retreating over the last three …