Due to a back injury he could not compete in 2007. He competed in the U-23 world Regatta in the double sculls event in 2002 with Igor Kuzmin, earning 7th position and in 2003 with Oleg Vinogradov earning 4th position. His first appearance in the was in Athens 2004, where he competed in the quadruple sculls event with Andrei Šilin, Kuzmin and Vinogradov earning 9th position overall.
In Beijing 2008 Jämsä competed in the single sculls event earning 17th position overall.
At the 2012 Summer Olympics, he again competed in the men"s quadruple sculls with Tõnu Endrekson, Allar Raja and Kaspar Taimsoo. The team finished 4th.
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. 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.
Gold medals went to Poland and silver medals to Ukraine.
Overall wins
Quadruple sculls: 2005.
He is a member of rowing club "Pärnu Sõudeklubi" (Pärnu Rowing Club) located in Pärnu.