The former Bees captain, 31, signed for the Gunners on Thursday.
Berta said: “We’re very pleased to welcome Christian Norgaard to the club. He has been a consistent high performer in the Premier League and brings many qualities to our club.
"He is a leader, and a player with high tactical intelligence and versatility who will have a very positive impact to the squad. We welcome Christian to Arsenal.”
Meanwhile, Norgaard admits he's excited to see what role manager Mikel Arteta has planned for him.
On his playing style, the Norway midfielder said: “It's developed a little bit over the years. I started as a more offensive player and now I'm a bit more of a holding midfielder. It's important for me that a team has a good defensive structure and hopefully I can contribute to that.
“Then coming off a season where I've had a lot of goal involvements, it's something I really hope I can take into this season as well.
“I don't know what the gaffer’s plans are with me, but hopefully I can also have some freedom to join the offensive play.”