James Markham Marshall Ambler was born in Markham, Virginia, on 30 December 1848. As a youth during the Civil War he served in a Virginia cavalry unit. He studied medicine at the University of Maryland, received a M.D. degree in 1870, and subsquently practiced in Baltimore. Appointed an Assistant Surgeon in the Navy in April 1874, he served initially in the practice ship Mayflower. During the next three years he was assigned to the gunboat Kansas, on the North Atlantic Station, and the frigate Minnesota, stationary training ship at the New York Navy Yard. From 1877 into 1879 Passed Assistant Surgeon Ambler was stationed at the Portsmouth Naval Hospital, near Norfolk, Virginia.

In 1879 Ambler joined the crew of the Arctic exploration steamer Jeannette, which sailed from San Francisco, California, in July 1879 to begin what would become a nearly two-year long expedition into the icepack north of Siberia. His medical skills were critical for maintaining the health of his shipmates during their long entrapment in the ice, and during their arduous journey over the rugged ice and frigid seas after the ship sank in June 1881.

Ambler was a member of expedition commander George W. Delong's boat crew, which landed at the northern end of the desolate Lena River Delta in September 1881. During the following weeks he treated his companions' frostbite and tried to maintain their strength as they slowly starved. Passed Assistant Surgeon Ambler was apparently one of the last three members of the group to succumb to hunger and exposure, sometime shortly after 30 October 1881.