His first appearance in the Olympic Games was in Athens 2004, where he competed in the quadruple sculls event with Andrei Šilin, Kuzmin and Vinogradov earning 9th position overall.

At the 2012 Summer Olympics, he again competed in the men's quadruple sculls with Tõnu Endrekson, Allar Raja and Kaspar Taimsoo.

[3] Jämsä's debut in the World Rowing Championships took place in Milan, Italy in 2003, where he competed in the double sculls event with Kuzmin earning 9th position overall.

Jämsä won his first World Championships medal in 2005 in Gifu, Japan in the quadruple sculls event with Tõnu Endrekson, Leonid Gulov and Jüri Jaanson when they finished third after Poland and Slovenia.

In the 2006 World Championships held in Eton, Great Britain Jämsä was again the strokesman in the bronze-winning quadruple sculls team with Endrekson, Kuzmin and Allar Raja.