'has somewhat changed' is correct and usable in written English.
You can use it when you want to express that something has slightly or moderately changed. For example: "The company's corporate culture has somewhat changed since the new CEO took over."
In his column today in The Jerusalem Post, Mr. Kuttab said that after reflection and debate he had somewhat changed his mind about the executions as necessary "radical deterrent steps" in the context of a "war".
"Well it was certainly one of the commitments that we made pre-election, but the circumstances have somewhat changed and sometimes one priority has to give way to a greater priority and the anti-terrorist campaign, the need for stronger counter-terrorism measures, is really absolutely critical right now," Abbott told the ABC.
A major theme of the episode is the humanization of "Caprica-Six" – while Caprica-Six shows her manipulative streak in parts of the episode, in particular during her conversation in the beach-side house with Boomer, the destruction of the Twelve Colonies and her love of Baltar have somewhat changed her psychology.
At 81 years old, Faustino is still spry and still doesn't go to town very often, but he has somewhat adapted to the changes surrounding him.
But there is a hint of indication that the Republican Party may have to somewhat change its tune from the usual patent demagoguery we are served on the ideological platter.
He has also changed somewhat in sensibility.
(This has, however, changed somewhat. As live performance opportunities have diminished since the 1960s, jazz musicians have adapted their approach, with the studio and rehearsals becoming more important to the process).
