He currently serves as a member of the Montana House of Representatives for District 98, which encompasses Missoula, for the Democratic Party since 2023.

Karlen graduated from the University of Montana with a Bachelor of Science in Wildlife biology with a minor in Climate Change Studies.

In 2020, Karlen was a Legislative Affairs Intern at the U.S. Forest Service, Office of the Chief in Washington, D.C. Karlen is an alumnus of the Max Baucus Leaders Program serving as a Legislative Intern for the U.S. Senate majority leader.

He is currently a board member of the Climate and Energy Board of Missoula, Montana and works as a Wildlife Research Associate of the Boone and Crockett Club based at the University of Montana, and coaches youth ski racing.

He is a member of the Natural Resources, Business and Labor, Legislative Administration, and Fish, Wildlife and Parks committees.