DULUTH, MN (KDAL) - The Mesabi Miner is loading coal today and the Superior Midwest Energy Terminal before heading to Marquette, Michigan. When the Miner leaves, late Tuesday or early Wednesday, it will officially open the 2013 commercial shipping season in the Twin Ports. Several other ships are also expected to leave the harbor later this week. The Soo Locks are scheduled to open on March 25th. Last season, the port of Duluth-Superior moved just under 37 million tons of cargo which was about the same as the previous year. Depending on weather patterns and global economies, Seaway Port Authority Executive Director Adoph Ojard is hoping for an increase in shipping activity this year.