Transferred to the United States Navy by Executive Order No. 8029 of 1 November 1941, Modoc joined the Greenland Patrol, whose orders were to do "a little of everything." This duty involved keeping convoy routes open, breaking and finding leads in ice for the Greenland convoys, escorting the convoys and rescuing survivors from torpedoed ships, constructing and maintaining aids to navigation, and reporting weather conditions.
Transferred to the United States Navy by Executive Order No. 8029 of 1 November 1941, Modoc joined the Greenland Patrol, whose duties were broad and varied. This involved maintaining safe passage for convoys, navigating ice floes, escorting convoys, rescuing survivors from torpedoed ships, constructing and maintaining navigational aids, and reporting weather conditions.