Clarke will oversee Modem's London and Frankfurt creative departments and will be charged with developing the agency's creative offering. He starts on 10 April.
Clarke replaces Chip Reingold, who has returned to San Francisco after two years heading Modem's European creative effort.
Reingold now takes a global creative role and will continue to work on international Modem clients including HP and GlaxoSmithKline.
The appointment of a British creative director is a significant step for the agency, which has a history of bringing management in from the US.
Norm Johnston, the managing director for Europe at Modem, said: "This is an opportunity for us to build our reputation as a top creative force. This year, our focus will be on creativity."
Clarke has worked at Wheel for four years, and was part of the management team involved in the sale of the agency to the Swedish group LB Icon in January 2005.