He was elected to the Norwegian Parliament from Finnmark in 1950, but was not re-elected in 1954. Instead he served in the position of deputy representative during the term 1954–1957.
Karlstrøm was a member of Talvik municipality council from 1931 to 1940 and 1945 to 1955, serving as mayor in the periods 1945–1947 and 1947–1951.
