BRUSSELS — NATO nations are sending troops to Norway for a cold-weather exercise this week, as alliance officials kick off a yearslong analysis into causes for conflict in the Arctic. As part of the planning effort, a U.S. and Norwegian-led research task force will compile a report by 2029 under the name “High North Scenarios for Wargaming and Analysis — Winter Storm 2030.” Beyond the lead nations, NATO countries to have thus far committed to participating in the Arctic security simulation