His father was grocer and brewery owner Johan Anthony Zinck Broch (1827–1923); his mother was Fanny Harriet Caroline Gamborg (1838–1926).

In 1910 he received a PhD degree in zoology, at which time he was named curator of the Royal Norwegian Society of Sciences and Letters (museum) in Trondheim.

In 1957 he was invited by the British Museum of Natural History to relocate to London to curate its amasses specimens.

He worked to improve conditions for marine life in Norway; he was chairman of the Association to promote fisheries in the Oslo Fjord in Drøbak (1932–1957).

He maintained a personal goal to publish at least one academic paper each year; his publication list includes about 180 works.