What was found
EXCESSIVE VIBRATION WAS COMING FROM THE NOSE GEAR AREA AFTER GEAR RETRACTION. FLIGHT RETURNED TO DTW AND LANDED WITHOUT INCIDENT. UPON INSPECTION, FOUND LEFT NOSE GEAR DOOR OPEN. ALSO, ICE WAS NOTED IN NOSE WELL AND AROUND DOOR. SECURED DOOR AND REMOVED ICE ACCUMULATION. AIRCRAFT RETURNED TO SERVICE.