Former Revere Mayor Thomas G. Ambrosino will officially begin his tenure as Chelsea’s city manager on Monday, July 20. The City Council last month chose Ambrosino from among two finalists for the position, which Jay Ash vacated in January to become the state’s housing and economic development secretary. Ash had been city manager since 2000. Ambrosino and councilors subsequently negotiated a four-year contract. Ambrosino served 12 years as Revere’s mayor. Since retiring in January 2012, he has been executive director of the state Supreme Judicial Court. Ned Keefe, Chelsea’s assistant city manager, is serving as acting manager. “I’m excited about this opportunity,” Ambrosino said in an interview. “Chelsea is a very vibrant community with lots of opportunities, and I’m looking forward to leading Chelsea to even better days ahead.”John Laidler can be reached at email@example.com.