President Obama on Tuesday will propose speeding the acquisition and building of new Coast Guard icebreakers that can operate year-round in the nation’s polar regions, part of an effort to close the gap between the United States and other nations, especially Russia, in a global competition to gain a foothold in the rapidly changing Arctic. On the second day of a three-day trip to Alaska to highlight the challenge of climate change and call for a worldwide effort to address its root causes, Mr. Obama’s proposals will touch on one of its most profound effects. The retreat of Arctic sea ice has created opportunities for shipping, tourism, mineral exploration and fishing — and with it, a rush of marine traffic that is bringing new difficulties. “Arctic ecosystems are among the most pristine and understudied in the world, meaning increased commercial activity comes with significant risks to the […]