Ensign Gardiner was a crew member of a PB5M Catalina patrol bomber with Patrol Squadron 46, U.S. Navy. He was Killed in Action while participating in aerial support over Korea on 5 November 1950. His remains were not recovered. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.

Gardiner was awarded the Purple Heart, the Combat Action Ribbon, the Korean Service Medal, the United Nations Service Medal, the National Defense Service Medal, the Korean Presidential Unit Citation and the Republic of Korea War Service Medal.